Migrate all controllers to REST API

src/main/java/org/example/petshopdesktop/DTOs/PurchaseOrderDTO.java

@@ -4,21 +4,21 @@ import javafx.beans.property.*;
 
 public class PurchaseOrderDTO {
 
-    private IntegerProperty purchaseOrderId;
+    private LongProperty purchaseOrderId;
     private StringProperty supplierName;
     private StringProperty orderDate;
     private StringProperty status;
 
-    public PurchaseOrderDTO(int id, String supplierName,
+    public PurchaseOrderDTO(long id, String supplierName,
                             String orderDate, String status) {
 
-        this.purchaseOrderId = new SimpleIntegerProperty(id);
+        this.purchaseOrderId = new SimpleLongProperty(id);
         this.supplierName = new SimpleStringProperty(supplierName);
         this.orderDate = new SimpleStringProperty(orderDate);
         this.status = new SimpleStringProperty(status);
     }
 
-    public int getPurchaseOrderId() { return purchaseOrderId.get(); }
+    public long getPurchaseOrderId() { return purchaseOrderId.get(); }
     public String getSupplierName() { return supplierName.get(); }
     public String getOrderDate() { return orderDate.get(); }
     public String getStatus() { return status.get(); }

src/main/java/org/example/petshopdesktop/api/dto/productsupplier/ProductSupplierResponse.java

@@ -4,6 +4,8 @@ import java.math.BigDecimal;
 
 public class ProductSupplierResponse {
     private Long id;
+    private Long productId;
+    private Long supplierId;
     private String productName;
     private String supplierName;
     private BigDecimal supplierPrice;
@@ -16,6 +18,22 @@ public class ProductSupplierResponse {
         this.id = id;
     }
 
+    public Long getProductId() {
+        return productId;
+    }
+
+    public void setProductId(Long productId) {
+        this.productId = productId;
+    }
+
+    public Long getSupplierId() {
+        return supplierId;
+    }
+
+    public void setSupplierId(Long supplierId) {
+        this.supplierId = supplierId;
+    }
+
     public String getProductName() {
         return productName;
     }

src/main/java/org/example/petshopdesktop/controllers/AdoptionController.java

@@ -1,5 +1,6 @@
 package org.example.petshopdesktop.controllers;
 
+import javafx.application.Platform;
 import javafx.collections.FXCollections;
 import javafx.collections.ObservableList;
 import javafx.event.ActionEvent;
@@ -10,15 +11,16 @@ import javafx.scene.control.*;
 import javafx.scene.control.cell.PropertyValueFactory;
 import javafx.stage.Modality;
 import javafx.stage.Stage;
+import org.example.petshopdesktop.api.dto.adoption.AdoptionResponse;
+import org.example.petshopdesktop.api.endpoints.AdoptionApi;
 import org.example.petshopdesktop.controllers.dialogcontrollers.AdoptionDialogController;
-import org.example.petshopdesktop.database.AdoptionDB;
 import org.example.petshopdesktop.models.Adoption;
 import org.example.petshopdesktop.util.ActivityLogger;
 
 import java.io.IOException;
-import java.sql.SQLException;
+import java.util.List;
-import java.sql.SQLIntegrityConstraintViolationException;
 import java.util.Optional;
+import java.util.stream.Collectors;
 
 public class AdoptionController {
 
@@ -35,7 +37,7 @@ public class AdoptionController {
     private TableColumn<Adoption, Integer> colAdoptionId;
 
     @FXML
-    private TableColumn<Adoption, Integer> colPetId;
+    private TableColumn<Adoption, String> colPetId;
 
     @FXML
     private TableColumn<Adoption, String> colCustomerName;
@@ -66,7 +68,7 @@ public class AdoptionController {
         tvAdoptions.getSelectionModel().setSelectionMode(javafx.scene.control.SelectionMode.MULTIPLE);
 
         colAdoptionId.setCellValueFactory(new PropertyValueFactory<>("adoptionId"));
-        colPetId.setCellValueFactory(new PropertyValueFactory<>("petId"));
+        colPetId.setCellValueFactory(new PropertyValueFactory<>("petName"));
         colCustomerName.setCellValueFactory(new PropertyValueFactory<>("customerName"));
         colAdoptionDate.setCellValueFactory(new PropertyValueFactory<>("adoptionDate"));
         colAdoptionFee.setCellValueFactory(new PropertyValueFactory<>("adoptionFee"));
@@ -118,47 +120,24 @@ public class AdoptionController {
 
         //if confirmed, start deletion
         if (result.isPresent() && result.get() == ButtonType.OK) {
-            int successCount = 0;
+            List<Long> ids = selectedAdoptions.stream()
-            int failCount = 0;
+                .map(a -> (long) a.getAdoptionId())
-            StringBuilder errors = new StringBuilder();
+                .collect(Collectors.toList());
 
-            for (Adoption adoption : selectedAdoptions) {
             try {
-                    int numRows = AdoptionDB.deleteAdoption(adoption.getAdoptionId());
+                AdoptionApi.getInstance().deleteAdoptions(ids);
-                    if (numRows > 0) {
-                        successCount++;
-                    } else {
-                        failCount++;
-                    }
-                }
-                catch (SQLIntegrityConstraintViolationException e) {
-                    ActivityLogger.getInstance().logException(
-                        "AdoptionController.btnDeleteClicked",
-                        e,
-                        String.format("Attempting to delete adoption ID %d - foreign key constraint", adoption.getAdoptionId()));
-                    failCount++;
-                    errors.append("Adoption ID ").append(adoption.getAdoptionId()).append(" is referenced in another table\n");
-                } catch (SQLException e) {
-                    ActivityLogger.getInstance().logException(
-                        "AdoptionController.btnDeleteClicked",
-                        e,
-                        String.format("Attempting to delete adoption ID %d", adoption.getAdoptionId()));
-                    failCount++;
-                    errors.append("Failed to delete adoption ID ").append(adoption.getAdoptionId()).append("\n");
-                }
-            }
-
-            //show results
-            if (failCount > 0) {
-                Alert alert = new Alert(Alert.AlertType.WARNING);
-                alert.setHeaderText("Delete Operation Completed with Errors");
-                alert.setContentText(String.format("Deleted: %d\nFailed: %d\n\n%s",
-                    successCount, failCount, errors.toString()));
-                alert.showAndWait();
-            } else if (successCount > 0) {
                 Alert alert = new Alert(Alert.AlertType.INFORMATION);
                 alert.setHeaderText("Database Operation Confirmed");
-                alert.setContentText("Successfully deleted " + successCount + " adoption record(s)");
+                alert.setContentText("Successfully deleted " + ids.size() + " adoption record(s)");
+                alert.showAndWait();
+            } catch (Exception e) {
+                ActivityLogger.getInstance().logException(
+                    "AdoptionController.btnDeleteClicked",
+                    e,
+                    "Deleting adoptions");
+                Alert alert = new Alert(Alert.AlertType.ERROR);
+                alert.setHeaderText("Delete Operation Failed");
+                alert.setContentText(e.getMessage());
                 alert.showAndWait();
             }
 
@@ -181,35 +160,55 @@ public class AdoptionController {
     }
 
     private void displayFilteredAdoptions(String filter) {
-        data.clear();
-        try {
         if (txtSearch.getText() == null || txtSearch.getText().isEmpty()) {
             displayAdoptions();
         } else {
-                data = AdoptionDB.getFilteredAdoptions(filter);
+            new Thread(() -> {
+                try {
+                    List<AdoptionResponse> adoptions = AdoptionApi.getInstance().listAdoptions(filter);
+                    List<Adoption> adoptionList = adoptions.stream()
+                        .map(this::mapToAdoption)
+                        .collect(Collectors.toList());
+
+                    Platform.runLater(() -> {
+                        data.setAll(adoptionList);
                         tvAdoptions.setItems(data);
-            }
+                    });
                 } catch (Exception e) {
+                    Platform.runLater(() -> {
+                        System.out.println("Error while fetching table data: " + e.getMessage());
                         ActivityLogger.getInstance().logException(
                             "AdoptionController.displayFilteredAdoptions",
                             e,
                             "Filtering adoptions with filter: " + filter);
-            System.out.println("Error while fetching table data: " + e.getMessage());
+                    });
+                }
+            }).start();
         }
     }
 
     private void displayAdoptions() {
-        data.clear();
+        new Thread(() -> {
             try {
-            data = AdoptionDB.getAdoptions();
+                List<AdoptionResponse> adoptions = AdoptionApi.getInstance().listAdoptions(null);
-        } catch (SQLException e) {
+                List<Adoption> adoptionList = adoptions.stream()
+                    .map(this::mapToAdoption)
+                    .collect(Collectors.toList());
+
+                Platform.runLater(() -> {
+                    data.setAll(adoptionList);
+                    tvAdoptions.setItems(data);
+                });
+            } catch (Exception e) {
+                Platform.runLater(() -> {
+                    System.out.println("Error while fetching table data: " + e.getMessage());
                     ActivityLogger.getInstance().logException(
                         "AdoptionController.displayAdoptions",
                         e,
                         "Fetching adoption data for table display");
-            System.out.println("Error while fetching table data: " + e.getMessage());
+                });
             }
-        tvAdoptions.setItems(data);
+        }).start();
     }
 
     private void openDialog(Adoption adoption, String mode) {
@@ -244,4 +243,17 @@ public class AdoptionController {
         btnEdit.setDisable(true);
         txtSearch.setText("");
     }
+
+    private Adoption mapToAdoption(AdoptionResponse response) {
+        return new Adoption(
+            response.getId().intValue(),
+            0,
+            0,
+            response.getPetName(),
+            response.getCustomerName(),
+            response.getAdoptionDate() != null ? response.getAdoptionDate().toString() : "",
+            0.0,
+            response.getAdoptionStatus()
+        );
+    }
 }

src/main/java/org/example/petshopdesktop/controllers/AnalyticsController.java

@@ -1,19 +1,25 @@
 package org.example.petshopdesktop.controllers;
 
-import javafx.collections.ObservableList;
+import javafx.application.Platform;
 import javafx.event.ActionEvent;
 import javafx.fxml.FXML;
 import javafx.scene.chart.*;
 import javafx.scene.control.Button;
 import javafx.scene.control.Label;
-import org.example.petshopdesktop.auth.UserSession;
+import org.example.petshopdesktop.api.dto.analytics.DailySales;
-import org.example.petshopdesktop.database.SaleDB;
+import org.example.petshopdesktop.api.dto.analytics.DashboardResponse;
-import org.example.petshopdesktop.models.analytics.*;
+import org.example.petshopdesktop.api.dto.analytics.TopProduct;
+import org.example.petshopdesktop.api.dto.sale.SaleResponse;
+import org.example.petshopdesktop.api.endpoints.AnalyticsApi;
+import org.example.petshopdesktop.api.endpoints.SaleApi;
 import org.example.petshopdesktop.util.ActivityLogger;
 
+import java.math.BigDecimal;
+import java.math.RoundingMode;
 import java.text.NumberFormat;
 import java.time.format.DateTimeFormatter;
-import java.util.Locale;
+import java.util.*;
+import java.util.stream.Collectors;
 
 public class AnalyticsController {
 
@@ -78,79 +84,111 @@ public class AnalyticsController {
 
     private void loadAnalyticsData() {
         lblError.setVisible(false);
+        new Thread(() -> {
             try {
-            loadSummaryData();
+                DashboardResponse dashboard = AnalyticsApi.getInstance().getDashboard(30, 10);
-            loadSalesOverTime();
+                List<SaleResponse> sales = SaleApi.getInstance().listSales(0, Integer.MAX_VALUE, null);
-            loadTopProductsByRevenue();
+
-            loadTopProductsByQuantity();
+                Platform.runLater(() -> {
-            loadPaymentMethodDistribution();
+                    try {
-            loadEmployeePerformance();
+                        loadSummaryData(dashboard);
+                        loadSalesOverTime(dashboard);
+                        loadTopProductsByRevenue(dashboard);
+                        loadTopProductsByQuantity(dashboard);
+                        loadPaymentMethodDistribution(sales);
+                        loadEmployeePerformance(sales);
                     } catch (Exception e) {
                         ActivityLogger.getInstance().logException("AnalyticsController.loadAnalyticsData", e, "Loading analytics data");
                         lblError.setText("Error loading analytics data. Please try again.");
                         lblError.setVisible(true);
                     }
+                });
+            } catch (Exception e) {
+                Platform.runLater(() -> {
+                    ActivityLogger.getInstance().logException("AnalyticsController.loadAnalyticsData", e, "Loading analytics data");
+                    lblError.setText("Error loading analytics data. Please try again.");
+                    lblError.setVisible(true);
+                });
+            }
+        }).start();
     }
 
-    private void loadSummaryData() throws Exception {
+    private void loadSummaryData(DashboardResponse dashboard) throws Exception {
-        SalesSummary summary = SaleDB.getSalesSummary();
+        if (dashboard != null) {
-        if (summary != null) {
+            BigDecimal totalRevenue = dashboard.getTotalRevenue() != null ? dashboard.getTotalRevenue() : BigDecimal.ZERO;
-            lblTotalRevenue.setText(currency.format(summary.getTotalRevenue()));
+            Long totalSales = dashboard.getTotalSales() != null ? dashboard.getTotalSales() : 0L;
-            lblTotalTransactions.setText(wholeNumber.format(summary.getTotalTransactions()));
+            Long totalProducts = dashboard.getTotalProducts() != null ? dashboard.getTotalProducts() : 0L;
-            lblAvgTransaction.setText(currency.format(summary.getAvgTransactionValue()));
+
-            lblTotalItems.setText(wholeNumber.format(summary.getTotalItemsSold()));
+            lblTotalRevenue.setText(currency.format(totalRevenue));
+            lblTotalTransactions.setText(wholeNumber.format(totalSales));
+
+            BigDecimal avgTransaction = BigDecimal.ZERO;
+            if (totalSales > 0) {
+                avgTransaction = totalRevenue.divide(BigDecimal.valueOf(totalSales), 2, RoundingMode.HALF_UP);
+            }
+            lblAvgTransaction.setText(currency.format(avgTransaction));
+            lblTotalItems.setText(wholeNumber.format(totalProducts));
         }
     }
 
-    private void loadSalesOverTime() throws Exception {
+    private void loadSalesOverTime(DashboardResponse dashboard) throws Exception {
-        ObservableList<DailySalesData> data = SaleDB.getDailySalesRevenue();
+        List<DailySales> dailySales = dashboard.getDailySales() != null ? dashboard.getDailySales() : new ArrayList<>();
         XYChart.Series<String, Number> series = new XYChart.Series<>();
         series.setName("Daily Revenue");
 
         DateTimeFormatter formatter = DateTimeFormatter.ofPattern("MMM dd");
-        for (DailySalesData dailySale : data) {
+        for (DailySales dailySale : dailySales) {
             String dateStr = dailySale.getDate().format(formatter);
-            series.getData().add(new XYChart.Data<>(dateStr, dailySale.getRevenue()));
+            BigDecimal totalSales = dailySale.getTotalSales() != null ? dailySale.getTotalSales() : BigDecimal.ZERO;
+            series.getData().add(new XYChart.Data<>(dateStr, totalSales));
         }
 
         chartSalesOverTime.getData().clear();
         chartSalesOverTime.getData().add(series);
     }
 
-    private void loadTopProductsByRevenue() throws Exception {
+    private void loadTopProductsByRevenue(DashboardResponse dashboard) throws Exception {
-        ObservableList<ProductSalesData> data = SaleDB.getTopProductsByRevenue(10);
+        List<TopProduct> topProducts = dashboard.getTopProducts() != null ? dashboard.getTopProducts() : new ArrayList<>();
         XYChart.Series<Number, String> series = new XYChart.Series<>();
         series.setName("Revenue");
 
-        for (ProductSalesData product : data) {
+        for (TopProduct product : topProducts) {
-            series.getData().add(new XYChart.Data<>(product.getTotalRevenue(), product.getProductName()));
+            BigDecimal totalRevenue = product.getTotalRevenue() != null ? product.getTotalRevenue() : BigDecimal.ZERO;
+            series.getData().add(new XYChart.Data<>(totalRevenue, product.getProductName()));
         }
 
         chartTopRevenue.getData().clear();
         chartTopRevenue.getData().add(series);
     }
 
-    private void loadTopProductsByQuantity() throws Exception {
+    private void loadTopProductsByQuantity(DashboardResponse dashboard) throws Exception {
-        ObservableList<ProductSalesData> data = SaleDB.getTopProductsByQuantity(10);
+        List<TopProduct> topProducts = dashboard.getTopProducts() != null ? dashboard.getTopProducts() : new ArrayList<>();
         XYChart.Series<Number, String> series = new XYChart.Series<>();
         series.setName("Quantity");
 
-        for (ProductSalesData product : data) {
+        for (TopProduct product : topProducts) {
-            series.getData().add(new XYChart.Data<>(product.getTotalQuantity(), product.getProductName()));
+            Integer quantitySold = product.getQuantitySold() != null ? product.getQuantitySold() : 0;
+            series.getData().add(new XYChart.Data<>(quantitySold, product.getProductName()));
         }
 
         chartTopQuantity.getData().clear();
         chartTopQuantity.getData().add(series);
     }
 
-    private void loadPaymentMethodDistribution() throws Exception {
+    private void loadPaymentMethodDistribution(List<SaleResponse> sales) throws Exception {
-        ObservableList<PaymentMethodData> data = SaleDB.getPaymentMethodDistribution();
+        Map<String, Long> paymentMethodCount = sales.stream()
+            .filter(sale -> sale.getIsRefund() == null || !sale.getIsRefund())
+            .collect(Collectors.groupingBy(
+                sale -> sale.getPaymentMethod() != null ? sale.getPaymentMethod() : "Unknown",
+                Collectors.counting()
+            ));
+
         chartPaymentMethods.getData().clear();
 
-        for (PaymentMethodData payment : data) {
+        for (Map.Entry<String, Long> entry : paymentMethodCount.entrySet()) {
             PieChart.Data slice = new PieChart.Data(
-                payment.getPaymentMethod() + " (" + payment.getTransactionCount() + ")",
+                entry.getKey() + " (" + entry.getValue() + ")",
-                payment.getTransactionCount()
+                entry.getValue()
             );
             chartPaymentMethods.getData().add(slice);
         }

src/main/java/org/example/petshopdesktop/controllers/AppointmentController.java

@@ -1,5 +1,6 @@
 package org.example.petshopdesktop.controllers;
 
+import javafx.application.Platform;
 import javafx.collections.FXCollections;
 import javafx.collections.ObservableList;
 import javafx.collections.transformation.FilteredList;
@@ -13,10 +14,14 @@ import javafx.stage.Modality;
 import javafx.stage.Stage;
 
 import org.example.petshopdesktop.DTOs.AppointmentDTO;
+import org.example.petshopdesktop.api.dto.appointment.AppointmentResponse;
+import org.example.petshopdesktop.api.endpoints.AppointmentApi;
 import org.example.petshopdesktop.controllers.dialogcontrollers.AppointmentDialogController;
-import org.example.petshopdesktop.database.AppointmentDB;
 import org.example.petshopdesktop.util.ActivityLogger;
 
+import java.util.List;
+import java.util.stream.Collectors;
+
 public class AppointmentController {
 
     @FXML private TableView<AppointmentDTO> tvAppointments;
@@ -71,41 +76,50 @@ public class AppointmentController {
     }
 
     private void loadAppointments(){
+        new Thread(() -> {
             try{
-            appointments.setAll(AppointmentDB.getAppointmentDTOs());
+                List<AppointmentResponse> responses = AppointmentApi.getInstance().listAppointments(null);
+                List<AppointmentDTO> appointmentDTOs = responses.stream()
+                    .map(this::mapToAppointmentDTO)
+                    .collect(Collectors.toList());
+
+                Platform.runLater(() -> {
+                    appointments.setAll(appointmentDTOs);
+                });
             }catch(Exception e){
+                Platform.runLater(() -> {
                     ActivityLogger.getInstance().logException(
                         "AppointmentController.loadAppointments",
                         e,
                         "Loading appointments for table display");
                     e.printStackTrace();
+                });
             }
+        }).start();
     }
 
     private void applyFilter(String text) {
-        if (filtered == null) {
+        String query = text == null || text.trim().isEmpty() ? null : text.trim();
-            return;
+        new Thread(() -> {
-        }
+            try {
+                List<AppointmentResponse> responses = AppointmentApi.getInstance().listAppointments(query);
+                List<AppointmentDTO> appointmentDTOs = responses.stream()
+                    .map(this::mapToAppointmentDTO)
+                    .collect(Collectors.toList());
 
-        String q = text == null ? "" : text.trim().toLowerCase();
+                Platform.runLater(() -> {
-        if (q.isEmpty()) {
+                    appointments.setAll(appointmentDTOs);
-            filtered.setPredicate(a -> true);
+                });
-            return;
+            } catch (Exception e) {
+                Platform.runLater(() -> {
+                    ActivityLogger.getInstance().logException(
+                        "AppointmentController.applyFilter",
+                        e,
+                        String.format("Filtering appointments with query: %s", query));
+                    e.printStackTrace();
+                });
             }
-
+        }).start();
-        filtered.setPredicate(a ->
-            String.valueOf(a.getAppointmentId()).contains(q)
-                || safe(a.getPetName()).contains(q)
-                || safe(a.getServiceName()).contains(q)
-                || safe(a.getAppointmentDate()).contains(q)
-                || safe(a.getAppointmentTime()).contains(q)
-                || safe(a.getCustomerName()).contains(q)
-                || safe(a.getAppointmentStatus()).contains(q)
-        );
-    }
-
-    private static String safe(String v) {
-        return v == null ? "" : v.toLowerCase();
     }
 
     @FXML
@@ -145,35 +159,24 @@ public class AppointmentController {
 
         //if confirmed, start deletion
         if (result.isPresent() && result.get() == ButtonType.OK) {
-            int successCount = 0;
+            List<Long> ids = selectedAppointments.stream()
-            int failCount = 0;
+                .map(a -> (long) a.getAppointmentId())
-            StringBuilder errors = new StringBuilder();
+                .collect(Collectors.toList());
 
-            for (AppointmentDTO appointment : selectedAppointments) {
+            try {
-                try{
+                AppointmentApi.getInstance().deleteAppointments(ids);
-                    AppointmentDB.deleteAppointment(appointment.getAppointmentId());
+                Alert alert = new Alert(Alert.AlertType.INFORMATION);
-                    successCount++;
+                alert.setHeaderText("Database Operation Confirmed");
-                }catch(Exception e){
+                alert.setContentText("Successfully deleted " + ids.size() + " appointment(s)");
+                alert.showAndWait();
+            } catch (Exception e) {
                 ActivityLogger.getInstance().logException(
                     "AppointmentController.btnDeleteClicked",
                     e,
-                        String.format("Attempting to delete appointment ID %d", appointment.getAppointmentId()));
+                    "Deleting appointments");
-                    failCount++;
+                Alert alert = new Alert(Alert.AlertType.ERROR);
-                    errors.append("Failed to delete appointment ID ").append(appointment.getAppointmentId()).append("\n");
+                alert.setHeaderText("Delete Operation Failed");
-                }
+                alert.setContentText(e.getMessage());
-            }
-
-            //show results
-            if (failCount > 0) {
-                Alert alert = new Alert(Alert.AlertType.WARNING);
-                alert.setHeaderText("Delete Operation Completed with Errors");
-                alert.setContentText(String.format("Deleted: %d\nFailed: %d\n\n%s",
-                    successCount, failCount, errors.toString()));
-                alert.showAndWait();
-            } else if (successCount > 0) {
-                Alert alert = new Alert(Alert.AlertType.INFORMATION);
-                alert.setHeaderText("Database Operation Confirmed");
-                alert.setContentText("Successfully deleted " + successCount + " appointment(s)");
                 alert.showAndWait();
             }
 
@@ -225,4 +228,19 @@ public class AppointmentController {
         alert.setContentText(msg);
         alert.showAndWait();
     }
+
+    private AppointmentDTO mapToAppointmentDTO(AppointmentResponse response) {
+        return new AppointmentDTO(
+            response.getId().intValue(),
+            0,
+            response.getCustomerName(),
+            0,
+            response.getPetNames(),
+            0,
+            response.getServiceName(),
+            response.getAppointmentDate().toString(),
+            response.getAppointmentTime().toString(),
+            response.getAppointmentStatus()
+        );
+    }
 }

src/main/java/org/example/petshopdesktop/controllers/InventoryController.java

@@ -1,5 +1,6 @@
 package org.example.petshopdesktop.controllers;
 
+import javafx.application.Platform;
 import javafx.collections.FXCollections;
 import javafx.collections.ObservableList;
 import javafx.event.ActionEvent;
@@ -10,15 +11,16 @@ import javafx.scene.control.*;
 import javafx.scene.control.cell.PropertyValueFactory;
 import javafx.stage.Modality;
 import javafx.stage.Stage;
+import org.example.petshopdesktop.api.dto.inventory.InventoryResponse;
+import org.example.petshopdesktop.api.endpoints.InventoryApi;
 import org.example.petshopdesktop.controllers.dialogcontrollers.InventoryDialogController;
-import org.example.petshopdesktop.database.InventoryDB;
 import org.example.petshopdesktop.models.Inventory;
 import org.example.petshopdesktop.util.ActivityLogger;
 
 import java.io.IOException;
-import java.sql.SQLException;
+import java.util.List;
-import java.sql.SQLIntegrityConstraintViolationException;
 import java.util.Optional;
+import java.util.stream.Collectors;
 
 public class InventoryController {
 
@@ -58,11 +60,9 @@ public class InventoryController {
     //Loads upon view bootup
     @FXML
     void initialize() {
-        //Buttons disabled until row is selected
         btnEdit.setDisable(true);
         btnDelete.setDisable(true);
-        //Enable multiple selection
+        tvInventory.getSelectionModel().setSelectionMode(javafx.scene.control.SelectionMode.SINGLE);
-        tvInventory.getSelectionModel().setSelectionMode(javafx.scene.control.SelectionMode.MULTIPLE);
 
         colInventoryId.setCellValueFactory(new PropertyValueFactory<>("inventoryId"));
         colProductId.setCellValueFactory(new PropertyValueFactory<>("prodId"));
@@ -71,19 +71,16 @@ public class InventoryController {
 
         displayInventory();
 
-        //Enables buttons when row is selected
         tvInventory.getSelectionModel().selectedItemProperty().addListener(
                 (observable, oldValue, newValue) -> {
                     btnEdit.setDisable(false);
                     btnDelete.setDisable(false);
                 });
 
-        //Filter as user types
         txtSearch.textProperty().addListener((observable, oldValue, newValue) -> {
             displayFilteredInventory(newValue);
         });
 
-        //EventListener for DELETE key
         tvInventory.setOnKeyPressed(event -> {
             if (event.getCode() == javafx.scene.input.KeyCode.DELETE) {
                 if (tvInventory.getSelectionModel().getSelectedItem() != null) {
@@ -100,71 +97,35 @@ public class InventoryController {
         openDialog(null, mode);
     }
 
-    //Prompts user for confirmation prior to deletion
     @FXML
     void btnDeleteClicked(ActionEvent event) {
-        //get selected inventory records
+        Inventory selectedInventory = tvInventory.getSelectionModel().getSelectedItem();
-        var selectedInventory = tvInventory.getSelectionModel().getSelectedItems();
+        if (selectedInventory == null) return;
-        if (selectedInventory.isEmpty()) return;
 
-        //ask user to confirm
         Alert question = new Alert(Alert.AlertType.CONFIRMATION);
         question.setHeaderText("Please confirm delete");
-        String message = selectedInventory.size() == 1
+        question.setContentText("Are you sure you want to delete this inventory record?");
-            ? "Are you sure you want to delete this inventory record?"
-            : "Are you sure you want to delete " + selectedInventory.size() + " inventory records?";
-        question.setContentText(message);
         question.getDialogPane().lookupButton(ButtonType.OK).requestFocus();
         Optional<ButtonType> result = question.showAndWait();
 
-        //if confirmed, start deletion
         if (result.isPresent() && result.get() == ButtonType.OK) {
-            int successCount = 0;
-            int failCount = 0;
-            StringBuilder errors = new StringBuilder();
-
-            for (Inventory inventory : selectedInventory) {
             try {
-                    int numRows = InventoryDB.deleteInventory(inventory.getInventoryId());
+                InventoryApi.getInstance().deleteInventory((long) selectedInventory.getInventoryId());
-                    if (numRows > 0) {
-                        successCount++;
-                    } else {
-                        failCount++;
-                    }
-                }
-                catch (SQLIntegrityConstraintViolationException e) {
-                    ActivityLogger.getInstance().logException(
-                        "InventoryController.btnDeleteClicked",
-                        e,
-                        String.format("Attempting to delete inventory ID %d - foreign key constraint", inventory.getInventoryId()));
-                    failCount++;
-                    errors.append("Inventory record '").append(inventory.getProdName()).append("' is referenced in another table\n");
-                }
-                catch (SQLException e) {
-                    ActivityLogger.getInstance().logException(
-                        "InventoryController.btnDeleteClicked",
-                        e,
-                        String.format("Attempting to delete inventory ID %d", inventory.getInventoryId()));
-                    failCount++;
-                    errors.append("Failed to delete '").append(inventory.getProdName()).append("'\n");
-                }
-            }
-
-            //show results
-            if (failCount > 0) {
-                Alert alert = new Alert(Alert.AlertType.WARNING);
-                alert.setHeaderText("Delete Operation Completed with Errors");
-                alert.setContentText(String.format("Deleted: %d\nFailed: %d\n\n%s",
-                    successCount, failCount, errors.toString()));
-                alert.showAndWait();
-            } else if (successCount > 0) {
                 Alert alert = new Alert(Alert.AlertType.INFORMATION);
                 alert.setHeaderText("Database Operation Confirmed");
-                alert.setContentText("Successfully deleted " + successCount + " inventory record(s)");
+                alert.setContentText("Successfully deleted inventory record");
+                alert.showAndWait();
+            } catch (Exception e) {
+                ActivityLogger.getInstance().logException(
+                    "InventoryController.btnDeleteClicked",
+                    e,
+                    "Deleting inventory");
+                Alert alert = new Alert(Alert.AlertType.ERROR);
+                alert.setHeaderText("Delete Operation Failed");
+                alert.setContentText(e.getMessage());
                 alert.showAndWait();
             }
 
-            //refresh display and reset inputs
             displayInventory();
             btnDelete.setDisable(true);
             btnEdit.setDisable(true);
@@ -183,66 +144,72 @@ public class InventoryController {
         }
     }
 
-    //Search filter
     private void displayFilteredInventory(String filter) {
-        data.clear();
-        try {
-            //If search box is empty, display all inventory
         if (txtSearch.getText() == null || txtSearch.getText().isEmpty()) {
             displayInventory();
-            }
+        } else {
+            new Thread(() -> {
+                try {
+                    List<InventoryResponse> inventories = InventoryApi.getInstance().listInventory(filter);
+                    List<Inventory> inventoryList = inventories.stream()
+                        .map(this::mapToInventory)
+                        .collect(Collectors.toList());
 
-            else {
+                    Platform.runLater(() -> {
-                data = InventoryDB.getFilteredInventory(filter);
+                        data.setAll(inventoryList);
                         tvInventory.setItems(data);
-            }
+                    });
-        }
+                } catch (Exception e) {
-
+                    Platform.runLater(() -> {
-        catch (Exception e) {
+                        System.out.println("Error while fetching table data: " + e.getMessage());
                         ActivityLogger.getInstance().logException(
                             "InventoryController.displayFilteredInventory",
                             e,
-                "Filtering inventory with filter: " + filter);
+                            String.format("Filtering inventory with keyword: %s", filter));
-            System.out.println("Error while fetching table data: " + e.getMessage());
+                    });
+                }
+            }).start();
         }
     }
 
-    //Displays all records from DB
     private void displayInventory() {
-        data.clear();
+        new Thread(() -> {
             try {
-            data = InventoryDB.getInventory();
+                List<InventoryResponse> inventories = InventoryApi.getInstance().listInventory(null);
-        }
+                List<Inventory> inventoryList = inventories.stream()
+                    .map(this::mapToInventory)
+                    .collect(Collectors.toList());
 
-        catch (SQLException e) {
+                Platform.runLater(() -> {
+                    data.setAll(inventoryList);
+                    tvInventory.setItems(data);
+                });
+            } catch (Exception e) {
+                Platform.runLater(() -> {
+                    System.out.println("Error while fetching table data: " + e.getMessage());
                     ActivityLogger.getInstance().logException(
                         "InventoryController.displayInventory",
                         e,
                         "Fetching inventory data for table display");
-            System.out.println("Error while fetching table data: " + e.getMessage());
+                });
             }
-        tvInventory.setItems(data);
+        }).start();
     }
 
-    //Opens inventory-dialog-view
     private void openDialog(Inventory inventory, String mode) {
-        //Opens FXML
         FXMLLoader fxmlLoader = new FXMLLoader(getClass().getResource("/org/example/petshopdesktop/dialogviews/inventory-dialog-view.fxml"));
         Scene scene = null;
 
         try {
             scene = new Scene(fxmlLoader.load());
-        }
+        } catch (IOException e) {
-
-        catch (IOException e) {
             ActivityLogger.getInstance().logException(
                 "InventoryController.openDialog",
                 e,
-                "Loading inventory dialog in " + mode + " mode");
+                String.format("Loading inventory dialog view in %s mode", mode));
             throw new RuntimeException(e);
         }
 
-        //Passes data and mode to the view
         InventoryDialogController dialogController = fxmlLoader.getController();
         dialogController.setMode(mode);
 
@@ -256,10 +223,22 @@ public class InventoryController {
         dialogStage.setScene(scene);
         dialogStage.showAndWait();
 
-        //Refresh inventory
         displayInventory();
         btnDelete.setDisable(true);
         btnEdit.setDisable(true);
         txtSearch.setText("");
     }
+
+    private Inventory mapToInventory(InventoryResponse response) {
+        return new Inventory(
+            response.getId().intValue(),
+            0,
+            response.getProductName(),
+            response.getCategoryName() != null ? response.getCategoryName() : "",
+            0,
+            response.getStoreName() != null ? response.getStoreName() : "",
+            response.getStockQuantity() != null ? response.getStockQuantity() : 0,
+            response.getReorderLevel() != null ? response.getReorderLevel() : 0
+        );
+    }
 }

src/main/java/org/example/petshopdesktop/controllers/ProductSupplierController.java

@@ -1,5 +1,6 @@
 package org.example.petshopdesktop.controllers;
 
+import javafx.application.Platform;
 import javafx.collections.FXCollections;
 import javafx.collections.ObservableList;
 import javafx.event.ActionEvent;
@@ -10,19 +11,16 @@ import javafx.scene.control.*;
 import javafx.scene.control.cell.PropertyValueFactory;
 import javafx.stage.Modality;
 import javafx.stage.Stage;
-import org.example.petshopdesktop.DTOs.ProductDTO;
 import org.example.petshopdesktop.DTOs.ProductSupplierDTO;
-import org.example.petshopdesktop.controllers.dialogcontrollers.ProductDialogController;
+import org.example.petshopdesktop.api.dto.productsupplier.ProductSupplierResponse;
+import org.example.petshopdesktop.api.endpoints.ProductSupplierApi;
 import org.example.petshopdesktop.controllers.dialogcontrollers.ProductSupplierDialogController;
-import org.example.petshopdesktop.database.ProductDB;
-import org.example.petshopdesktop.database.ProductSupplierDB;
-import org.example.petshopdesktop.models.ProductSupplier;
 import org.example.petshopdesktop.util.ActivityLogger;
 
 import java.io.IOException;
-import java.sql.SQLException;
+import java.util.List;
-import java.sql.SQLIntegrityConstraintViolationException;
 import java.util.Optional;
+import java.util.stream.Collectors;
 
 public class ProductSupplierController {
 
@@ -107,22 +105,27 @@ public class ProductSupplierController {
      * Display the ProductSupplierDTO to table view
      */
     private void displayProductSupplier() {
-        //Erase old content
+        new Thread(() -> {
-        data.clear();
+            try {
+                List<ProductSupplierResponse> productSuppliers = ProductSupplierApi.getInstance().listProductSuppliers(null);
+                List<ProductSupplierDTO> productSupplierDTOs = productSuppliers.stream()
+                    .map(this::mapToProductSupplierDTO)
+                    .collect(Collectors.toList());
 
-        //get ProductSupplier from database
+                Platform.runLater(() -> {
-        try{
+                    data.setAll(productSupplierDTOs);
-            data = ProductSupplierDB.getProductSupplierDTO();
+                    tvProductSuppliers.setItems(data);
-        } catch (SQLException e) {
+                });
+            } catch (Exception e) {
+                Platform.runLater(() -> {
+                    System.out.println("Error while fetching table data: " + e.getMessage());
                     ActivityLogger.getInstance().logException(
                         "ProductSupplierController.displayProductSupplier",
                         e,
                         "Fetching product-supplier data for table display");
-            System.out.println("Error while fetching table data: " + e.getMessage());
+                });
             }
-
+        }).start();
-        //put data in the table
-        tvProductSuppliers.setItems(data);
     }
 
     /**
@@ -130,22 +133,30 @@ public class ProductSupplierController {
      * @param filter word to filter table
      */
     private void displayFilteredProductSupplier(String filter){
-        data.clear();
-        try{
         if (txtSearch.getText() == null || txtSearch.getText().isEmpty()){
-                displayProductSupplier(); //If search bar is empty just display everything
+            displayProductSupplier();
-            }
+        } else {
-            else{
+            new Thread(() -> {
-                //Filter the using the keyword
+                try {
-                data = ProductSupplierDB.getFilteredProductSupplierDTO(filter);
+                    List<ProductSupplierResponse> productSuppliers = ProductSupplierApi.getInstance().listProductSuppliers(filter);
+                    List<ProductSupplierDTO> productSupplierDTOs = productSuppliers.stream()
+                        .map(this::mapToProductSupplierDTO)
+                        .collect(Collectors.toList());
+
+                    Platform.runLater(() -> {
+                        data.setAll(productSupplierDTOs);
                         tvProductSuppliers.setItems(data);
-            }
+                    });
                 } catch (Exception e) {
+                    Platform.runLater(() -> {
+                        System.out.println("Error while fetching table data: " + e.getMessage());
                         ActivityLogger.getInstance().logException(
                             "ProductSupplierController.displayFilteredProductSupplier",
                             e,
                             "Filtering product-supplier data with filter: " + filter);
-            System.out.println("Error while fetching table data: " + e.getMessage());
+                    });
+                }
+            }).start();
         }
     }
 
@@ -181,52 +192,24 @@ public class ProductSupplierController {
 
         //if confirmed, start deletion
         if (result.isPresent() && result.get() == ButtonType.OK) {
-            int successCount = 0;
+            List<Long> ids = selectedProductSuppliers.stream()
-            int failCount = 0;
+                .map(ps -> (long) ps.getSupId())
-            StringBuilder errors = new StringBuilder();
+                .collect(Collectors.toList());
 
-            for (ProductSupplierDTO productSupplier : selectedProductSuppliers) {
+            try {
-                try{
+                ProductSupplierApi.getInstance().deleteProductSuppliers(ids);
-                    int numRows = ProductSupplierDB.deleteProductSupplier(productSupplier.getSupId(), productSupplier.getProdId());
-                    if (numRows > 0) {
-                        successCount++;
-                    } else {
-                        failCount++;
-                    }
-                }
-                catch (SQLIntegrityConstraintViolationException e){
-                    ActivityLogger.getInstance().logException(
-                        "ProductSupplierController.btnDeleteClicked",
-                        e,
-                        String.format("Attempting to delete product-supplier - SupID: %d, ProdID: %d - foreign key constraint",
-                            productSupplier.getSupId(), productSupplier.getProdId()));
-                    failCount++;
-                    errors.append(String.format("Product-Supplier '%s - %s' is referenced in another table\n",
-                        productSupplier.getProdName(), productSupplier.getSupCompany()));
-                }
-                catch (SQLException e) {
-                    ActivityLogger.getInstance().logException(
-                        "ProductSupplierController.btnDeleteClicked",
-                        e,
-                        String.format("Attempting to delete product-supplier - SupID: %d, ProdID: %d",
-                            productSupplier.getSupId(), productSupplier.getProdId()));
-                    failCount++;
-                    errors.append(String.format("Failed to delete '%s - %s'\n",
-                        productSupplier.getProdName(), productSupplier.getSupCompany()));
-                }
-            }
-
-            //show results
-            if (failCount > 0) {
-                Alert alert = new Alert(Alert.AlertType.WARNING);
-                alert.setHeaderText("Delete Operation Completed with Errors");
-                alert.setContentText(String.format("Deleted: %d\nFailed: %d\n\n%s",
-                    successCount, failCount, errors.toString()));
-                alert.showAndWait();
-            } else if (successCount > 0) {
                 Alert alert = new Alert(Alert.AlertType.INFORMATION);
                 alert.setHeaderText("Database Operation Confirmed");
-                alert.setContentText("Successfully deleted " + successCount + " product-supplier(s)");
+                alert.setContentText("Successfully deleted " + ids.size() + " product-supplier(s)");
+                alert.showAndWait();
+            } catch (Exception e) {
+                ActivityLogger.getInstance().logException(
+                    "ProductSupplierController.btnDeleteClicked",
+                    e,
+                    "Deleting product-suppliers");
+                Alert alert = new Alert(Alert.AlertType.ERROR);
+                alert.setHeaderText("Delete Operation Failed");
+                alert.setContentText(e.getMessage());
                 alert.showAndWait();
             }
 
@@ -297,4 +280,14 @@ public class ProductSupplierController {
         txtSearch.setText("");
     }
 
+    private ProductSupplierDTO mapToProductSupplierDTO(ProductSupplierResponse response) {
+        return new ProductSupplierDTO(
+            response.getSupplierId().intValue(),
+            response.getProductId().intValue(),
+            response.getSupplierName(),
+            response.getProductName(),
+            response.getSupplierPrice().doubleValue()
+        );
+    }
+
 }

src/main/java/org/example/petshopdesktop/controllers/PurchaseOrderController.java

@@ -1,5 +1,6 @@
 package org.example.petshopdesktop.controllers;
 
+import javafx.application.Platform;
 import javafx.collections.FXCollections;
 import javafx.collections.ObservableList;
 import javafx.collections.transformation.FilteredList;
@@ -7,9 +8,13 @@ import javafx.fxml.FXML;
 import javafx.scene.control.*;
 import javafx.scene.control.cell.PropertyValueFactory;
 import org.example.petshopdesktop.DTOs.PurchaseOrderDTO;
-import org.example.petshopdesktop.database.PurchaseOrderDB;
+import org.example.petshopdesktop.api.dto.purchaseorder.PurchaseOrderResponse;
+import org.example.petshopdesktop.api.endpoints.PurchaseOrderApi;
 import org.example.petshopdesktop.util.ActivityLogger;
 
+import java.util.List;
+import java.util.stream.Collectors;
+
 public class PurchaseOrderController {
 
     @FXML private Button btnRefresh;
@@ -19,7 +24,7 @@ public class PurchaseOrderController {
 
     @FXML private TableView<PurchaseOrderDTO> tvPurchaseOrders;
 
-    @FXML private TableColumn<PurchaseOrderDTO,Integer> colOrderId;
+    @FXML private TableColumn<PurchaseOrderDTO,Long> colOrderId;
     @FXML private TableColumn<PurchaseOrderDTO,String> colSupplier;
     @FXML private TableColumn<PurchaseOrderDTO,String> colOrderDate;
     @FXML private TableColumn<PurchaseOrderDTO,String> colStatus;
@@ -53,17 +58,28 @@ public class PurchaseOrderController {
     }
 
     private void loadPurchaseOrders() {
+        new Thread(() -> {
             try {
-            purchaseOrders.setAll(PurchaseOrderDB.getPurchaseOrders());
+                List<PurchaseOrderResponse> responses = PurchaseOrderApi.getInstance().listPurchaseOrders(null);
+                List<PurchaseOrderDTO> dtos = responses.stream()
+                    .map(this::mapToPurchaseOrderDTO)
+                    .collect(Collectors.toList());
+
+                Platform.runLater(() -> {
+                    purchaseOrders.setAll(dtos);
+                    tvPurchaseOrders.setItems(filtered);
+                });
             } catch (Exception e) {
+                Platform.runLater(() -> {
                     ActivityLogger.getInstance().logException(
                         "PurchaseOrderController.loadPurchaseOrders",
                         e,
                         "Loading purchase orders for table display");
-            e.printStackTrace();
                     new Alert(Alert.AlertType.ERROR,
                             "Unable to load purchase orders").showAndWait();
+                });
             }
+        }).start();
     }
 
     private void applyFilter(String text) {
@@ -93,4 +109,13 @@ public class PurchaseOrderController {
     void btnRefresh() {
         loadPurchaseOrders();
     }
+
+    private PurchaseOrderDTO mapToPurchaseOrderDTO(PurchaseOrderResponse response) {
+        return new PurchaseOrderDTO(
+            response.getId(),
+            response.getSupplierName(),
+            response.getOrderDate() != null ? response.getOrderDate().toString() : "",
+            response.getOrderStatus()
+        );
+    }
 }

src/main/java/org/example/petshopdesktop/controllers/SaleController.java

@@ -22,20 +22,25 @@ import javafx.scene.layout.VBox;
 import javafx.stage.Modality;
 import javafx.stage.Stage;
 import org.example.petshopdesktop.auth.UserSession;
-import org.example.petshopdesktop.database.InventoryDB;
+import javafx.concurrent.Task;
-import org.example.petshopdesktop.database.ProductDB;
+import org.example.petshopdesktop.api.endpoints.ProductApi;
-import org.example.petshopdesktop.database.SaleDB;
+import org.example.petshopdesktop.api.endpoints.SaleApi;
-import org.example.petshopdesktop.models.Inventory;
+import org.example.petshopdesktop.api.dto.product.ProductResponse;
+import org.example.petshopdesktop.api.dto.sale.SaleItemRequest;
+import org.example.petshopdesktop.api.dto.sale.SaleItemResponse;
+import org.example.petshopdesktop.api.dto.sale.SaleRequest;
+import org.example.petshopdesktop.api.dto.sale.SaleResponse;
 import org.example.petshopdesktop.models.Product;
 import org.example.petshopdesktop.models.SaleCartItem;
 import org.example.petshopdesktop.models.SaleLineItem;
 import org.example.petshopdesktop.util.ActivityLogger;
 
-import java.sql.SQLException;
+import java.math.BigDecimal;
 import java.text.NumberFormat;
-import java.util.HashMap;
+import java.time.format.DateTimeFormatter;
+import java.util.ArrayList;
+import java.util.List;
 import java.util.Locale;
-import java.util.Map;
 
 public class SaleController {
 
@@ -124,8 +129,8 @@ public class SaleController {
     private final ObservableList<SaleLineItem> saleItems = FXCollections.observableArrayList();
     private FilteredList<SaleLineItem> filteredSales;
 
-    private final Map<Integer, Integer> inventoryByProdId = new HashMap<>();
     private final NumberFormat currency = NumberFormat.getCurrencyInstance(Locale.CANADA);
+    private static final DateTimeFormatter DATE_FORMATTER = DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm");
 
     @FXML
     public void initialize() {
@@ -133,7 +138,6 @@ public class SaleController {
         setupCreateSale();
         applyRoleMode();
 
-        refreshInventory();
         refreshSales();
     }
 
@@ -170,11 +174,20 @@ public class SaleController {
         updateCartTotal();
 
         try {
-            cbProduct.setItems(ProductDB.getProducts());
+            List<ProductResponse> productResponses = ProductApi.getInstance().listProducts(null);
-        } catch (SQLException e) {
+            ObservableList<Product> products = FXCollections.observableArrayList();
+            for (ProductResponse pr : productResponses) {
+                products.add(new Product(
+                    pr.getId().intValue(),
+                    pr.getProductName(),
+                    pr.getPrice().doubleValue(),
+                    0,
+                    pr.getDescription()
+                ));
+            }
+            cbProduct.setItems(products);
+        } catch (Exception e) {
             ActivityLogger.getInstance().logException("SaleController.setupCreateSale", e, "Loading products");
-        } catch (RuntimeException e) {
-            ActivityLogger.getInstance().logException("SaleController.setupCreateSale", e, "Database connection");
         }
     }
 
@@ -185,42 +198,59 @@ public class SaleController {
         lblModeNote.setText(isAdmin ? "(View only)" : "(Staff can create sales)");
     }
 
-    private void refreshInventory() {
-        inventoryByProdId.clear();
-        try {
-            for (Inventory inv : InventoryDB.getInventory()) {
-                inventoryByProdId.put(inv.getProdId(), inv.getQuantity());
-            }
-        } catch (SQLException e) {
-            ActivityLogger.getInstance().logException("SaleController.refreshInventory", e, "Loading inventory");
-        } catch (RuntimeException e) {
-            ActivityLogger.getInstance().logException("SaleController.refreshInventory", e, "Database connection");
-        }
-    }
-
     private void refreshSales() {
         refreshSales(false);
     }
 
     private void refreshSales(boolean showErrorDialog) {
-        try {
+        Task<List<SaleLineItem>> task = new Task<List<SaleLineItem>>() {
-            saleItems.setAll(SaleDB.getSaleLineItems());
+            @Override
-        } catch (SQLException e) {
+            protected List<SaleLineItem> call() throws Exception {
+                List<SaleResponse> sales = SaleApi.getInstance().listSales(0, 1000, null);
+                List<SaleLineItem> lineItems = new ArrayList<>();
+
+                for (SaleResponse sale : sales) {
+                    String saleDate = sale.getSaleDate() != null
+                        ? sale.getSaleDate().format(DATE_FORMATTER)
+                        : "";
+
+                    if (sale.getItems() != null && !sale.getItems().isEmpty()) {
+                        for (SaleItemResponse item : sale.getItems()) {
+                            lineItems.add(new SaleLineItem(
+                                sale.getId().intValue(),
+                                saleDate,
+                                sale.getEmployeeName(),
+                                item.getProductName(),
+                                item.getQuantity(),
+                                item.getUnitPrice().doubleValue(),
+                                item.getLineTotal().doubleValue(),
+                                sale.getPaymentMethod(),
+                                sale.getIsRefund() != null && sale.getIsRefund()
+                            ));
+                        }
+                    }
+                }
+                return lineItems;
+            }
+        };
+
+        task.setOnSucceeded(event -> {
+            saleItems.setAll(task.getValue());
+        });
+
+        task.setOnFailed(event -> {
+            Throwable e = task.getException();
             ActivityLogger.getInstance().logException("SaleController.refreshSales", e, "Loading sales");
             if (showErrorDialog) {
-                showError("Sales", "Could not load sales.");
+                showError("Sales", "Could not load sales: " + e.getMessage());
-            }
-        } catch (RuntimeException e) {
-            ActivityLogger.getInstance().logException("SaleController.refreshSales", e, "Database connection");
-            if (showErrorDialog) {
-                showError("Sales", "Database is not connected.");
-            }
             }
+        });
+
+        new Thread(task).start();
     }
 
     @FXML
     void btnRefresh(ActionEvent event) {
-        refreshInventory();
         refreshSales(true);
     }
 
@@ -244,18 +274,6 @@ public class SaleController {
             return;
         }
 
-        int stock = inventoryByProdId.getOrDefault(product.getProdId(), 0);
-        int alreadyInCart = cartItems.stream()
-            .filter(i -> i.getProdId() == product.getProdId())
-            .mapToInt(SaleCartItem::getQuantity)
-            .sum();
-
-        int available = stock - alreadyInCart;
-        if (requestedQty > available) {
-            showError("Create Sale", "Not enough stock. Available: " + Math.max(0, available));
-            return;
-        }
-
         for (SaleCartItem item : cartItems) {
             if (item.getProdId() == product.getProdId()) {
                 item.setQuantity(item.getQuantity() + requestedQty);
@@ -291,9 +309,9 @@ public class SaleController {
             return;
         }
 
-        Integer employeeId = UserSession.getInstance().getEmployeeId();
+        Long storeId = UserSession.getInstance().getStoreId();
-        if (employeeId == null || employeeId <= 0) {
+        if (storeId == null || storeId <= 0) {
-            showError("Create Sale", "Employee is not set for this account.");
+            showError("Create Sale", "Store is not set for this account.");
             return;
         }
 
@@ -309,20 +327,35 @@ public class SaleController {
         }
 
         try {
-            int saleId = SaleDB.createSale(employeeId, payment, cartItems);
+            SaleRequest request = new SaleRequest();
-            showInfo("Sale saved", "Sale ID " + saleId + " was created.");
+            request.setStoreId(storeId);
+            request.setPaymentMethod(payment);
+
+            List<SaleItemRequest> itemRequests = new ArrayList<>();
+            for (SaleCartItem cartItem : cartItems) {
+                SaleItemRequest itemRequest = new SaleItemRequest();
+                itemRequest.setProductId((long) cartItem.getProdId());
+                itemRequest.setQuantity(cartItem.getQuantity());
+                itemRequest.setUnitPrice(BigDecimal.valueOf(cartItem.getUnitPrice()));
+                itemRequests.add(itemRequest);
+            }
+            request.setItems(itemRequests);
+
+            SaleResponse response = SaleApi.getInstance().createSale(request);
+            showInfo("Sale saved", "Sale ID " + response.getId() + " was created.");
 
             cartItems.clear();
             updateCartTotal();
 
-            refreshInventory();
             refreshSales(true);
-        } catch (SQLException e) {
+        } catch (Exception e) {
             ActivityLogger.getInstance().logException("SaleController.btnSaveSale", e, "Creating sale");
-            showError("Create Sale", e.getMessage() == null ? "Could not save the sale." : e.getMessage());
+            String errorMsg = e.getMessage();
-        } catch (RuntimeException e) {
+            if (errorMsg != null && errorMsg.contains("Insufficient inventory")) {
-            ActivityLogger.getInstance().logException("SaleController.btnSaveSale", e, "Database connection");
+                showError("Create Sale", "Insufficient stock for one or more items.");
-            showError("Create Sale", "Database is not connected.");
+            } else {
+                showError("Create Sale", errorMsg != null ? errorMsg : "Could not save the sale.");
+            }
         }
     }
 

src/main/java/org/example/petshopdesktop/controllers/ServiceController.java

@@ -1,8 +1,8 @@
 package org.example.petshopdesktop.controllers;
 
+import javafx.application.Platform;
 import javafx.collections.FXCollections;
 import javafx.collections.ObservableList;
-import javafx.collections.transformation.FilteredList;
 import javafx.event.ActionEvent;
 import javafx.fxml.FXML;
 import javafx.fxml.FXMLLoader;
@@ -10,12 +10,17 @@ import javafx.scene.Scene;
 import javafx.scene.control.*;
 import javafx.scene.control.cell.PropertyValueFactory;
 import javafx.stage.Stage;
-import org.example.petshopdesktop.database.ServiceDB;
+import org.example.petshopdesktop.DTOs.ServiceDTO;
-import org.example.petshopdesktop.models.Service;
+import org.example.petshopdesktop.api.dto.service.ServiceResponse;
+import org.example.petshopdesktop.api.endpoints.ServiceApi;
 import org.example.petshopdesktop.controllers.dialogcontrollers.ServiceDialogController;
 import org.example.petshopdesktop.util.ActivityLogger;
 import javafx.stage.Modality;
 
+import java.util.List;
+import java.util.Optional;
+import java.util.stream.Collectors;
+
 
 public class ServiceController {
 
@@ -23,22 +28,23 @@ public class ServiceController {
     @FXML private Button btnDelete;
     @FXML private Button btnEdit;
 
-    @FXML private TableColumn<Service, Integer> colServiceId;
+    @FXML private TableColumn<ServiceDTO, Integer> colServiceId;
-    @FXML private TableColumn<Service, String> colServiceName;
+    @FXML private TableColumn<ServiceDTO, String> colServiceName;
-    @FXML private TableColumn<Service, String> colServiceDesc;
+    @FXML private TableColumn<ServiceDTO, String> colServiceDesc;
-    @FXML private TableColumn<Service, Integer> colServiceDuration;
+    @FXML private TableColumn<ServiceDTO, Integer> colServiceDuration;
-    @FXML private TableColumn<Service, Double> colServicePrice;
+    @FXML private TableColumn<ServiceDTO, Double> colServicePrice;
 
-    @FXML private TableView<Service> tvServices;
+    @FXML private TableView<ServiceDTO> tvServices;
 
     @FXML private TextField txtSearch;
 
-    private final ObservableList<Service> services = FXCollections.observableArrayList();
+    private ObservableList<ServiceDTO> data = FXCollections.observableArrayList();
-    private FilteredList<Service> filtered;
+    private String mode = null;
 
     @FXML
     public void initialize() {
-        //Enable multiple selection
+        btnEdit.setDisable(true);
+        btnDelete.setDisable(true);
         tvServices.getSelectionModel().setSelectionMode(javafx.scene.control.SelectionMode.MULTIPLE);
 
         colServiceId.setCellValueFactory(new PropertyValueFactory<>("serviceId"));
@@ -47,14 +53,19 @@ public class ServiceController {
         colServiceDuration.setCellValueFactory(new PropertyValueFactory<>("serviceDuration"));
         colServicePrice.setCellValueFactory(new PropertyValueFactory<>("servicePrice"));
 
-        filtered = new FilteredList<>(services, s -> true);
+        displayServices();
-        tvServices.setItems(filtered);
 
-        if (txtSearch != null) {
+        tvServices.getSelectionModel().selectedItemProperty().addListener(
-            txtSearch.textProperty().addListener((obs, o, n) -> applyFilter(n));
+            (observable, oldValue, newValue) -> {
+                btnEdit.setDisable(false);
+                btnDelete.setDisable(false);
             }
+        );
+
+        txtSearch.textProperty().addListener((observable, oldValue, newValue) -> {
+            displayFilteredServices(newValue);
+        });
 
-        //EventListener for DELETE key
         tvServices.setOnKeyPressed(event -> {
             if (event.getCode() == javafx.scene.input.KeyCode.DELETE) {
                 if (tvServices.getSelectionModel().getSelectedItem() != null) {
@@ -62,75 +73,82 @@ public class ServiceController {
                 }
             }
         });
-
-        loadServices();
     }
 
-    private void loadServices() {
+    private void displayServices() {
+        new Thread(() -> {
             try {
-            services.setAll(ServiceDB.getServices());
+                List<ServiceResponse> services = ServiceApi.getInstance().listServices(null);
+                List<ServiceDTO> serviceDTOs = services.stream()
+                    .map(this::mapToServiceDTO)
+                    .collect(Collectors.toList());
+
+                Platform.runLater(() -> {
+                    data.setAll(serviceDTOs);
+                    tvServices.setItems(data);
+                });
             } catch (Exception e) {
+                Platform.runLater(() -> {
+                    System.out.println("Error while fetching table data: " + e.getMessage());
                     ActivityLogger.getInstance().logException(
-                "ServiceController.loadServices",
+                        "ServiceController.displayServices",
                         e,
-                "Loading services for table display");
+                        "Fetching service data for table display");
-            showAlert("Database Error", "Unable to load services.");
+                });
-            e.printStackTrace();
             }
+        }).start();
     }
 
-    private void applyFilter(String text) {
+    private void displayFilteredServices(String filter) {
-        if (filtered == null) {
+        if (txtSearch.getText() == null || txtSearch.getText().isEmpty()) {
-            return;
+            displayServices();
-        }
+        } else {
+            new Thread(() -> {
+                try {
+                    List<ServiceResponse> services = ServiceApi.getInstance().listServices(filter);
+                    List<ServiceDTO> serviceDTOs = services.stream()
+                        .map(this::mapToServiceDTO)
+                        .collect(Collectors.toList());
 
-        String q = text == null ? "" : text.trim().toLowerCase();
+                    Platform.runLater(() -> {
-        if (q.isEmpty()) {
+                        data.setAll(serviceDTOs);
-            filtered.setPredicate(s -> true);
+                        tvServices.setItems(data);
-            return;
+                    });
+                } catch (Exception e) {
+                    Platform.runLater(() -> {
+                        System.out.println("Error while fetching table data: " + e.getMessage());
+                        ActivityLogger.getInstance().logException(
+                            "ServiceController.displayFilteredServices",
+                            e,
+                            String.format("Filtering services with keyword: %s", filter));
+                    });
                 }
-
+            }).start();
-        filtered.setPredicate(s ->
-            String.valueOf(s.getServiceId()).contains(q)
-                || safe(s.getServiceName()).contains(q)
-                || safe(s.getServiceDesc()).contains(q)
-                || String.valueOf(s.getServiceDuration()).contains(q)
-                || String.valueOf(s.getServicePrice()).contains(q)
-        );
         }
-
-    private static String safe(String v) {
-        return v == null ? "" : v.toLowerCase();
     }
 
 
     @FXML
     void btnAddClicked(ActionEvent event) {
-        openDialog(null, "Add");
+        mode = "Add";
-        loadServices();
+        openDialog(null, mode);
     }
 
     @FXML
     void btnEditClicked(ActionEvent event) {
+        ServiceDTO selected = tvServices.getSelectionModel().getSelectedItem();
 
-        Service selected = tvServices.getSelectionModel().getSelectedItem();
+        if (selected != null) {
-
+            mode = "Edit";
-        if (selected == null) {
+            openDialog(selected, mode);
-            showAlert("Select Service", "Please select a service to edit.");
-            return;
         }
-
-        openDialog(selected, "Edit");
-        loadServices();
     }
 
     @FXML
-    void btnDeleteClicked(ActionEvent e) {
+    void btnDeleteClicked(ActionEvent event) {
-        //get selected services
         var selectedServices = tvServices.getSelectionModel().getSelectedItems();
         if (selectedServices.isEmpty()) return;
 
-        //ask user to confirm
         Alert question = new Alert(Alert.AlertType.CONFIRMATION);
         question.setHeaderText("Please confirm delete");
         String message = selectedServices.size() == 1
@@ -138,82 +156,78 @@ public class ServiceController {
             : "Are you sure you want to delete " + selectedServices.size() + " services?";
         question.setContentText(message);
         question.getDialogPane().lookupButton(ButtonType.OK).requestFocus();
-        java.util.Optional<ButtonType> result = question.showAndWait();
+        Optional<ButtonType> result = question.showAndWait();
 
-        //if confirmed, start deletion
         if (result.isPresent() && result.get() == ButtonType.OK) {
-            int successCount = 0;
+            List<Long> ids = selectedServices.stream()
-            int failCount = 0;
+                .map(s -> (long) s.getServiceId())
-            StringBuilder errors = new StringBuilder();
+                .collect(Collectors.toList());
 
-            for (Service service : selectedServices) {
             try {
-                    ServiceDB.deleteService(service.getServiceId());
+                ServiceApi.getInstance().deleteServices(ids);
-                    successCount++;
-                } catch (Exception ex) {
-                    ActivityLogger.getInstance().logException(
-                        "ServiceController.btnDeleteClicked",
-                        ex,
-                        String.format("Attempting to delete service ID %d", service.getServiceId()));
-                    failCount++;
-                    errors.append("Failed to delete '").append(service.getServiceName()).append("'\n");
-                }
-            }
-
-            //show results
-            if (failCount > 0) {
-                Alert alert = new Alert(Alert.AlertType.WARNING);
-                alert.setHeaderText("Delete Operation Completed with Errors");
-                alert.setContentText(String.format("Deleted: %d\nFailed: %d\n\n%s",
-                    successCount, failCount, errors.toString()));
-                alert.showAndWait();
-            } else if (successCount > 0) {
                 Alert alert = new Alert(Alert.AlertType.INFORMATION);
                 alert.setHeaderText("Database Operation Confirmed");
-                alert.setContentText("Successfully deleted " + successCount + " service(s)");
+                alert.setContentText("Successfully deleted " + ids.size() + " service(s)");
+                alert.showAndWait();
+            } catch (Exception e) {
+                ActivityLogger.getInstance().logException(
+                    "ServiceController.btnDeleteClicked",
+                    e,
+                    "Deleting services");
+                Alert alert = new Alert(Alert.AlertType.ERROR);
+                alert.setHeaderText("Delete Operation Failed");
+                alert.setContentText(e.getMessage());
                 alert.showAndWait();
             }
 
-            //refresh display
+            displayServices();
-            loadServices();
+            btnDelete.setDisable(true);
+            btnEdit.setDisable(true);
+            txtSearch.setText("");
         }
     }
 
-    private void openDialog(Service service, String mode) {
+    private void openDialog(ServiceDTO service, String mode) {
-
+        FXMLLoader fxmlLoader = new FXMLLoader(getClass().getResource("/org/example/petshopdesktop/dialogviews/service-dialog-view.fxml"));
+        Scene scene = null;
         try {
-            FXMLLoader loader = new FXMLLoader(
+            scene = new Scene(fxmlLoader.load());
-                    getClass().getResource("/org/example/petshopdesktop/dialogviews/service-dialog-view.fxml")
-            );
-
-            Stage stage = new Stage();
-            stage.setScene(new Scene(loader.load()));
-
-            ServiceDialogController controller = loader.getController();
-            controller.setMode(mode);
-
-            if (mode.equals("Edit")) {
-                controller.setService(service);
-            }
-
-            stage.initModality(Modality.APPLICATION_MODAL);
-            stage.showAndWait();
-
-            loadServices();
-
         } catch (Exception e) {
             ActivityLogger.getInstance().logException(
                 "ServiceController.openDialog",
                 e,
-                "Opening service dialog in " + mode + " mode");
+                String.format("Loading service dialog view in %s mode", mode));
-            e.printStackTrace();
+            throw new RuntimeException(e);
         }
+        ServiceDialogController dialogController = fxmlLoader.getController();
+        dialogController.setMode(mode);
+
+        if (mode.equals("Edit")) {
+            dialogController.setService(service);
         }
-    private void showAlert(String title, String msg) {
+        Stage dialogStage = new Stage();
-        Alert alert = new Alert(Alert.AlertType.INFORMATION);
+        dialogStage.initModality(Modality.APPLICATION_MODAL);
-        alert.setTitle(title);
+        if (mode.equals("Add")) {
-        alert.setHeaderText(null);
+            dialogStage.setTitle("Add Service");
-        alert.setContentText(msg);
+        } else {
-        alert.showAndWait();
+            dialogStage.setTitle("Edit Service");
+        }
+        dialogStage.setScene(scene);
+        dialogStage.showAndWait();
+
+        displayServices();
+        btnDelete.setDisable(true);
+        btnEdit.setDisable(true);
+        txtSearch.setText("");
+    }
+
+    private ServiceDTO mapToServiceDTO(ServiceResponse response) {
+        return new ServiceDTO(
+            response.getId().intValue(),
+            response.getServiceName(),
+            response.getDescription(),
+            0,
+            response.getPrice().doubleValue()
+        );
     }
 }

src/main/java/org/example/petshopdesktop/controllers/StaffAccountsController.java

@@ -1,5 +1,6 @@
 package org.example.petshopdesktop.controllers;
 
+import javafx.application.Platform;
 import javafx.collections.FXCollections;
 import javafx.collections.ObservableList;
 import javafx.collections.transformation.FilteredList;
@@ -15,12 +16,16 @@ import javafx.scene.control.TextField;
 import javafx.scene.control.cell.PropertyValueFactory;
 import javafx.stage.Modality;
 import javafx.stage.Stage;
+import org.example.petshopdesktop.api.dto.user.UserResponse;
+import org.example.petshopdesktop.api.endpoints.UserApi;
 import org.example.petshopdesktop.auth.UserSession;
-import org.example.petshopdesktop.database.UserDB;
 import org.example.petshopdesktop.models.StaffAccount;
 import org.example.petshopdesktop.util.ActivityLogger;
 
-import java.sql.SQLException;
+import java.sql.Timestamp;
+import java.time.ZoneId;
+import java.util.List;
+import java.util.stream.Collectors;
 
 public class StaffAccountsController {
 
@@ -107,15 +112,54 @@ public class StaffAccountsController {
 
     private void refresh() {
         lblError.setText("");
+        tvStaff.setDisable(true);
+
+        new Thread(() -> {
             try {
-            staffAccounts.setAll(UserDB.getStaffAccounts());
+                List<UserResponse> users = UserApi.getInstance().listUsers(null);
-        } catch (SQLException e) {
+                List<StaffAccount> accounts = users.stream()
+                    .map(this::mapToStaffAccount)
+                    .collect(Collectors.toList());
+
+                Platform.runLater(() -> {
+                    staffAccounts.setAll(accounts);
+                    tvStaff.setDisable(false);
+                });
+            } catch (Exception e) {
                 ActivityLogger.getInstance().logException("StaffAccountsController.refresh", e, "Loading staff accounts");
+                Platform.runLater(() -> {
                     lblError.setText("Could not load staff accounts.");
-        } catch (RuntimeException e) {
+                    tvStaff.setDisable(false);
-            ActivityLogger.getInstance().logException("StaffAccountsController.refresh", e, "Database connection");
+                });
-            lblError.setText("Database is not connected.");
             }
+        }).start();
+    }
+
+    private StaffAccount mapToStaffAccount(UserResponse user) {
+        long id = user.getId() != null ? user.getId() : 0L;
+        String username = user.getUsername();
+        String fullName = user.getFullName() != null ? user.getFullName() : "";
+        String[] names = splitFullName(fullName);
+        String firstName = names[0];
+        String lastName = names[1];
+        String email = "";
+        String phone = "";
+        boolean active = user.getActive() != null ? user.getActive() : false;
+        Timestamp createdAt = user.getCreatedAt() != null
+            ? Timestamp.from(user.getCreatedAt().atZone(ZoneId.systemDefault()).toInstant())
+            : null;
+
+        return new StaffAccount(id, id, username, firstName, lastName, email, phone, active, createdAt);
+    }
+
+    private String[] splitFullName(String fullName) {
+        if (fullName == null || fullName.trim().isEmpty()) {
+            return new String[]{"", ""};
+        }
+        String[] parts = fullName.trim().split("\\s+", 2);
+        String firstName = parts.length > 0 ? parts[0] : "";
+        String lastName = parts.length > 1 ? parts[1] : "";
+        return new String[]{firstName, lastName};
     }
 
     private void applyFilter(String text) {

src/main/java/org/example/petshopdesktop/controllers/SupplierController.java

@@ -1,5 +1,6 @@
 package org.example.petshopdesktop.controllers;
 
+import javafx.application.Platform;
 import javafx.collections.FXCollections;
 import javafx.collections.ObservableList;
 import javafx.event.ActionEvent;
@@ -10,15 +11,16 @@ import javafx.scene.control.*;
 import javafx.scene.control.cell.PropertyValueFactory;
 import javafx.stage.Modality;
 import javafx.stage.Stage;
+import org.example.petshopdesktop.api.dto.supplier.SupplierResponse;
+import org.example.petshopdesktop.api.endpoints.SupplierApi;
 import org.example.petshopdesktop.controllers.dialogcontrollers.SupplierDialogController;
-import org.example.petshopdesktop.database.SupplierDB;
 import org.example.petshopdesktop.models.Supplier;
 import org.example.petshopdesktop.util.ActivityLogger;
 
 import java.io.IOException;
-import java.sql.SQLException;
+import java.util.List;
-import java.sql.SQLIntegrityConstraintViolationException;
 import java.util.Optional;
+import java.util.stream.Collectors;
 
 /**
  * The controller for any operations in the supplier view
@@ -105,19 +107,27 @@ public class SupplierController {
      * Display the suppliers to table view
      */
     private void displaySupplier(){
-        data.clear();
+        new Thread(() -> {
+            try {
+                List<SupplierResponse> suppliers = SupplierApi.getInstance().listSuppliers(null);
+                List<Supplier> supplierList = suppliers.stream()
+                    .map(this::mapToSupplier)
+                    .collect(Collectors.toList());
 
-        try{
+                Platform.runLater(() -> {
-            data = SupplierDB.getSuppliers();
+                    data.setAll(supplierList);
-        } catch (SQLException e) {
+                    tvSuppliers.setItems(data);
+                });
+            } catch (Exception e) {
+                Platform.runLater(() -> {
+                    System.out.println("Error while fetching table data: " + e.getMessage());
                     ActivityLogger.getInstance().logException(
                         "SupplierController.displaySupplier",
                         e,
                         "Fetching supplier data for table display");
-            System.out.println("Error while fetching table data: " + e.getMessage());
+                });
             }
-
+        }).start();
-        tvSuppliers.setItems(data);
     }
 
     /**
@@ -125,22 +135,30 @@ public class SupplierController {
      * @param filter word to filter table
      */
     private void displayFilteredSupplier(String filter){
-        data.clear();
-        try{
         if (txtSearch.getText() == null || txtSearch.getText().isEmpty()){
-                displaySupplier(); //If search bar is empty just display everything
+            displaySupplier();
-            }
+        } else {
-            else{
+            new Thread(() -> {
-                //Filter the using the keyword
+                try {
-                data = SupplierDB.getFilteredSuppliers(filter);
+                    List<SupplierResponse> suppliers = SupplierApi.getInstance().listSuppliers(filter);
+                    List<Supplier> supplierList = suppliers.stream()
+                        .map(this::mapToSupplier)
+                        .collect(Collectors.toList());
+
+                    Platform.runLater(() -> {
+                        data.setAll(supplierList);
                         tvSuppliers.setItems(data);
-            }
+                    });
                 } catch (Exception e) {
+                    Platform.runLater(() -> {
+                        System.out.println("Error while fetching table data: " + e.getMessage());
                         ActivityLogger.getInstance().logException(
                             "SupplierController.displayFilteredSupplier",
                             e,
                             "Filtering suppliers with filter: " + filter);
-            System.out.println("Error while fetching table data: " + e.getMessage());
+                    });
+                }
+            }).start();
         }
     }
 
@@ -177,48 +195,24 @@ public class SupplierController {
 
         //if confirmed, start deletion
         if (result.isPresent() && result.get() == ButtonType.OK) {
-            int successCount = 0;
+            List<Long> ids = selectedSuppliers.stream()
-            int failCount = 0;
+                .map(s -> (long) s.getSupId())
-            StringBuilder errors = new StringBuilder();
+                .collect(Collectors.toList());
 
-            for (Supplier supplier : selectedSuppliers) {
+            try {
-                try{
+                SupplierApi.getInstance().deleteSuppliers(ids);
-                    int numRows = SupplierDB.deleteSupplier(supplier.getSupId());
-                    if (numRows > 0) {
-                        successCount++;
-                    } else {
-                        failCount++;
-                    }
-                }
-                catch (SQLIntegrityConstraintViolationException e){
-                    ActivityLogger.getInstance().logException(
-                        "SupplierController.btnDeleteClicked",
-                        e,
-                        String.format("Attempting to delete supplier ID %d - foreign key constraint", supplier.getSupId()));
-                    failCount++;
-                    errors.append("Supplier '").append(supplier.getSupCompany()).append("' is referenced in another table\n");
-                }
-                catch (SQLException e) {
-                    ActivityLogger.getInstance().logException(
-                        "SupplierController.btnDeleteClicked",
-                        e,
-                        String.format("Attempting to delete supplier ID %d", supplier.getSupId()));
-                    failCount++;
-                    errors.append("Failed to delete '").append(supplier.getSupCompany()).append("'\n");
-                }
-            }
-
-            //show results
-            if (failCount > 0) {
-                Alert alert = new Alert(Alert.AlertType.WARNING);
-                alert.setHeaderText("Delete Operation Completed with Errors");
-                alert.setContentText(String.format("Deleted: %d\nFailed: %d\n\n%s",
-                    successCount, failCount, errors.toString()));
-                alert.showAndWait();
-            } else if (successCount > 0) {
                 Alert alert = new Alert(Alert.AlertType.INFORMATION);
                 alert.setHeaderText("Database Operation Confirmed");
-                alert.setContentText("Successfully deleted " + successCount + " supplier(s)");
+                alert.setContentText("Successfully deleted " + ids.size() + " supplier(s)");
+                alert.showAndWait();
+            } catch (Exception e) {
+                ActivityLogger.getInstance().logException(
+                    "SupplierController.btnDeleteClicked",
+                    e,
+                    "Deleting suppliers");
+                Alert alert = new Alert(Alert.AlertType.ERROR);
+                alert.setHeaderText("Delete Operation Failed");
+                alert.setContentText(e.getMessage());
                 alert.showAndWait();
             }
 
@@ -290,4 +284,20 @@ public class SupplierController {
         txtSearch.setText("");
     }
 
+    private Supplier mapToSupplier(SupplierResponse response) {
+        String contactPerson = response.getContactPerson() != null ? response.getContactPerson() : "";
+        String[] nameParts = contactPerson.split(" ", 2);
+        String firstName = nameParts.length > 0 ? nameParts[0] : "";
+        String lastName = nameParts.length > 1 ? nameParts[1] : "";
+
+        return new Supplier(
+            response.getId().intValue(),
+            response.getSupplierName(),
+            firstName,
+            lastName,
+            response.getEmail(),
+            response.getPhone()
+        );
+    }
+
 }

src/main/java/org/example/petshopdesktop/controllers/dialogcontrollers/AdoptionDialogController.java

@@ -1,5 +1,6 @@
 package org.example.petshopdesktop.controllers.dialogcontrollers;
 
+import javafx.application.Platform;
 import javafx.collections.FXCollections;
 import javafx.collections.ObservableList;
 import javafx.event.EventHandler;
@@ -12,16 +13,15 @@ import javafx.scene.control.DatePicker;
 import javafx.scene.control.Label;
 import javafx.scene.input.MouseEvent;
 import javafx.stage.Stage;
-import javafx.util.StringConverter;
+import org.example.petshopdesktop.api.dto.adoption.AdoptionRequest;
-import org.example.petshopdesktop.database.AdoptionDB;
+import org.example.petshopdesktop.api.dto.common.DropdownOption;
-import org.example.petshopdesktop.database.PetDB;
+import org.example.petshopdesktop.api.endpoints.AdoptionApi;
+import org.example.petshopdesktop.api.endpoints.DropdownApi;
 import org.example.petshopdesktop.models.Adoption;
-import org.example.petshopdesktop.models.Customer;
-import org.example.petshopdesktop.models.Pet;
 import org.example.petshopdesktop.util.ActivityLogger;
 
-import java.sql.SQLException;
 import java.time.LocalDate;
+import java.util.List;
 
 public class AdoptionDialogController {
 
@@ -36,10 +36,10 @@ public class AdoptionDialogController {
     private ComboBox<String> cbAdoptionStatus;
 
     @FXML
-    private ComboBox<Customer> cbCustomer;
+    private ComboBox<DropdownOption> cbCustomer;
 
     @FXML
-    private ComboBox<Pet> cbPet;
+    private ComboBox<DropdownOption> cbPet;
 
     @FXML
     private DatePicker dpAdoptionDate;
@@ -58,52 +58,47 @@ public class AdoptionDialogController {
             "Pending", "Completed", "Cancelled"
     );
 
-    //Loads upon boot
     @FXML
     void initialize() {
 
-        //Loads statusList into combo box
         cbAdoptionStatus.setItems(statusList);
 
-        //Pet objects are converted into readable text for combobox (PetID + PetName)
+        new Thread(() -> {
-        cbPet.setConverter(new StringConverter<Pet>() {
-            @Override
-            public String toString(Pet pet) {
-                return pet == null ? "" : pet.getPetId() + ": " + pet.getPetName();
-            }
-
-            //Not used
-            @Override
-            public Pet fromString(String string) { return null; }
-        });
-
-        //Load pets from DB into pet combobox
             try {
-            cbPet.setItems(PetDB.getPets());
+                List<DropdownOption> pets = DropdownApi.getInstance().getPets();
-        }
+                Platform.runLater(() -> {
-
+                    ObservableList<DropdownOption> petsObs = FXCollections.observableArrayList(pets);
-        catch (SQLException e) {
+                    cbPet.setItems(petsObs);
+                });
+            } catch (Exception e) {
+                Platform.runLater(() -> {
                     ActivityLogger.getInstance().logException(
                         "AdoptionDialogController.initialize",
                         e,
                         "Loading pets for combo box");
                     System.out.println("Error loading pets: " + e.getMessage());
+                });
             }
+        }).start();
 
-        //Load customers from DB into customer combobox
+        new Thread(() -> {
             try {
-            cbCustomer.setItems(AdoptionDB.getCustomers());
+                List<DropdownOption> customers = DropdownApi.getInstance().getCustomers();
-        }
+                Platform.runLater(() -> {
-
+                    ObservableList<DropdownOption> customersObs = FXCollections.observableArrayList(customers);
-        catch (SQLException e) {
+                    cbCustomer.setItems(customersObs);
+                });
+            } catch (Exception e) {
+                Platform.runLater(() -> {
                     ActivityLogger.getInstance().logException(
                         "AdoptionDialogController.initialize",
                         e,
                         "Loading customers for combo box");
                     System.out.println("Error loading customers: " + e.getMessage());
+                });
             }
+        }).start();
 
-        //Save button handler
         btnSave.setOnMouseClicked(new EventHandler<MouseEvent>() {
             @Override
             public void handle(MouseEvent mouseEvent) {
@@ -111,7 +106,6 @@ public class AdoptionDialogController {
             }
         });
 
-        //Cancel button handler, closes dialog view
         btnCancel.setOnMouseClicked(new EventHandler<MouseEvent>() {
             @Override
             public void handle(MouseEvent mouseEvent) {
@@ -120,12 +114,9 @@ public class AdoptionDialogController {
         });
     }
 
-    //Handles logic when clicking Save
     private void buttonSaveClicked(MouseEvent mouseEvent) {
-        int numRow = 0;
         String errorMsg = "";
 
-        //Validation: checks if anything is missing
         if (cbPet.getSelectionModel().getSelectedItem() == null) {
             errorMsg += "Pet is required.\n";
         }
@@ -142,60 +133,37 @@ public class AdoptionDialogController {
             errorMsg += "Status is required.\n";
         }
 
-        //If no errors, attempt DB operation
         if (errorMsg.isEmpty()) {
-            Adoption adoption = collectAdoption();
+            try {
+                AdoptionRequest request = new AdoptionRequest();
+                request.setPetId(cbPet.getSelectionModel().getSelectedItem().getId());
+                request.setCustomerId(cbCustomer.getSelectionModel().getSelectedItem().getId());
+                request.setAdoptionDate(dpAdoptionDate.getValue());
+                request.setAdoptionStatus(cbAdoptionStatus.getValue());
 
-            //Try inserting into DB
                 if (mode.equals("Add")) {
-                try {
+                    AdoptionApi.getInstance().createAdoption(request);
-                    numRow = AdoptionDB.insertAdoption(adoption);
+                } else {
+                    Long adoptionId = Long.parseLong(lblAdoptionId.getText().split(": ")[1]);
+                    AdoptionApi.getInstance().updateAdoption(adoptionId, request);
                 }
 
-                catch (SQLException e) {
-                    ActivityLogger.getInstance().logException(
-                        "AdoptionDialogController.buttonSaveClicked",
-                        e,
-                        "Inserting new adoption record");
-                    throw new RuntimeException(e);
-                }
-            }
-
-            //Try updating adoption
-            else {
-                try {
-                    numRow = AdoptionDB.updateAdoption(adoption.getAdoptionId(), adoption);
-                }
-
-                catch (SQLException e) {
-                    ActivityLogger.getInstance().logException(
-                        "AdoptionDialogController.buttonSaveClicked",
-                        e,
-                        "Updating adoption with ID: " + adoption.getAdoptionId());
-                    throw new RuntimeException(e);
-                }
-            }
-
-            //If no rows are affected, an issue has occurred
-            if (numRow == 0) {
-                Alert alert = new Alert(Alert.AlertType.ERROR);
-                alert.setHeaderText("Database Operation Error");
-                alert.setContentText(mode + " failed");
-                alert.showAndWait();
-            }
-
-            //DB operation worked!
-            else {
                 Alert alert = new Alert(Alert.AlertType.INFORMATION);
                 alert.setHeaderText("Saved");
                 alert.setContentText(mode + " succeeded");
                 alert.showAndWait();
                 closeStage(mouseEvent);
+            } catch (Exception e) {
+                ActivityLogger.getInstance().logException(
+                    "AdoptionDialogController.buttonSaveClicked",
+                    e,
+                    mode + " adoption");
+                Alert alert = new Alert(Alert.AlertType.ERROR);
+                alert.setHeaderText("Database Operation Error");
+                alert.setContentText(e.getMessage());
+                alert.showAndWait();
             }
-        }
+        } else {
-
-        //If there are errors, display them
-        else {
             Alert alert = new Alert(Alert.AlertType.ERROR);
             alert.setHeaderText("Input Error");
             alert.setContentText(errorMsg);
@@ -203,30 +171,6 @@ public class AdoptionDialogController {
         }
     }
 
-    //Collects user input, builds an Adoption object
-    private Adoption collectAdoption() {
-        int adoptionId = 0;
-
-        //Only grab adoption ID if in edit mode
-        if (lblAdoptionId.isVisible()) {
-            adoptionId = Integer.parseInt(lblAdoptionId.getText().split(": ")[1]);
-        }
-
-        Pet selectedPet = cbPet.getSelectionModel().getSelectedItem();
-        Customer selectedCustomer = cbCustomer.getSelectionModel().getSelectedItem();
-        String date = dpAdoptionDate.getValue().toString();
-        String status = cbAdoptionStatus.getValue();
-
-        return new Adoption(
-                adoptionId,
-                selectedPet.getPetId(),
-                selectedCustomer.getCustomerId(),
-                selectedCustomer.toString(),
-                date,
-                selectedPet.getPetPrice(),
-                status
-        );
-    }
 
     private void closeStage(MouseEvent mouseEvent) {
         Node node = (Node) mouseEvent.getSource();
@@ -234,35 +178,28 @@ public class AdoptionDialogController {
         stage.close();
     }
 
-    //Edit mode
-    //Inserts data into fields
     public void displayAdoptionDetails(Adoption adoption) {
         if (adoption != null) {
-            //Displays adoption ID
             lblAdoptionId.setText("ID: " + adoption.getAdoptionId());
 
-            //Select pet
+            for (DropdownOption pet : cbPet.getItems()) {
-            for (Pet pet : cbPet.getItems()) {
+                if (pet.getLabel().equals(adoption.getPetName())) {
-                if (pet.getPetId() == adoption.getPetId()) {
                     cbPet.getSelectionModel().select(pet);
                     break;
                 }
             }
 
-            //Select customer
+            for (DropdownOption customer : cbCustomer.getItems()) {
-            for (Customer customer : cbCustomer.getItems()) {
+                if (customer.getLabel().equals(adoption.getCustomerName())) {
-                if (customer.getCustomerId() == adoption.getCustomerId()) {
                     cbCustomer.getSelectionModel().select(customer);
                     break;
                 }
             }
 
-            //Select adoption date
             if (adoption.getAdoptionDate() != null && !adoption.getAdoptionDate().isEmpty()) {
                 dpAdoptionDate.setValue(LocalDate.parse(adoption.getAdoptionDate()));
             }
 
-            //Select adoption status
             for (String status : cbAdoptionStatus.getItems()) {
                 if (status.equals(adoption.getAdoptionStatus())) {
                     cbAdoptionStatus.getSelectionModel().select(status);
@@ -272,8 +209,6 @@ public class AdoptionDialogController {
         }
     }
 
-    //Sets dialog mode
-    //Also updates label and adoption ID visibility
     public void setMode(String mode) {
         this.mode = mode;
         lblMode.setText(mode + " Adoption");

src/main/java/org/example/petshopdesktop/controllers/dialogcontrollers/AppointmentDialogController.java

@@ -1,5 +1,6 @@
 package org.example.petshopdesktop.controllers.dialogcontrollers;
 
+import javafx.application.Platform;
 import javafx.collections.FXCollections;
 import javafx.collections.ObservableList;
 import javafx.fxml.FXML;
@@ -10,11 +11,16 @@ import javafx.stage.Stage;
 import javafx.scene.control.ListCell;
 
 import org.example.petshopdesktop.DTOs.AppointmentDTO;
-import org.example.petshopdesktop.database.*;
+import org.example.petshopdesktop.api.dto.appointment.AppointmentRequest;
-import org.example.petshopdesktop.models.*;
+import org.example.petshopdesktop.api.dto.appointment.AppointmentResponse;
+import org.example.petshopdesktop.api.dto.common.DropdownOption;
+import org.example.petshopdesktop.api.endpoints.AppointmentApi;
+import org.example.petshopdesktop.api.endpoints.DropdownApi;
 import org.example.petshopdesktop.util.ActivityLogger;
 
-import java.sql.Time;
+import java.time.LocalTime;
+import java.util.Collections;
+import java.util.List;
 
 public class AppointmentDialogController {
 
@@ -25,9 +31,9 @@ public class AppointmentDialogController {
     @FXML private Button btnCancel;
     @FXML private Button btnSave;
 
-    @FXML private ComboBox<Service> cbService;
+    @FXML private ComboBox<DropdownOption> cbService;
-    @FXML private ComboBox<Customer> cbCustomer;
+    @FXML private ComboBox<DropdownOption> cbCustomer;
-    @FXML private ComboBox<Pet> cbPet;
+    @FXML private ComboBox<DropdownOption> cbPet;
 
     @FXML private ComboBox<Integer> cbHour;
     @FXML private ComboBox<Integer> cbMinute;
@@ -67,17 +73,27 @@ public class AppointmentDialogController {
     @FXML
     public void initialize() {
 
+        new Thread(() -> {
             try {
-            cbService.setItems(ServiceDB.getServices());
+                List<DropdownOption> services = DropdownApi.getInstance().getServices();
-            cbCustomer.setItems(CustomerDB.getCustomers());
+                List<DropdownOption> customers = DropdownApi.getInstance().getCustomers();
-            cbPet.setItems(PetDB.getPets());
+                List<DropdownOption> pets = DropdownApi.getInstance().getPets();
+
+                Platform.runLater(() -> {
+                    cbService.setItems(FXCollections.observableArrayList(services));
+                    cbCustomer.setItems(FXCollections.observableArrayList(customers));
+                    cbPet.setItems(FXCollections.observableArrayList(pets));
+                });
             } catch (Exception e) {
+                Platform.runLater(() -> {
                     ActivityLogger.getInstance().logException(
                         "AppointmentDialogController.initialize",
                         e,
                         "Loading combo box data for services, customers, and pets");
                     e.printStackTrace();
+                });
             }
+        }).start();
 
         cbAppointmentStatus.setItems(statusList);
 
@@ -88,20 +104,49 @@ public class AppointmentDialogController {
 
         cbMinute.getItems().addAll(0, 15, 30, 45);
 
-        // Show pet name
+        // Show dropdown labels
-        cbPet.setCellFactory(param -> new ListCell<>() {
+        cbService.setCellFactory(param -> new ListCell<>() {
             @Override
-            protected void updateItem(Pet pet, boolean empty) {
+            protected void updateItem(DropdownOption option, boolean empty) {
-                super.updateItem(pet, empty);
+                super.updateItem(option, empty);
-                setText(empty || pet == null ? null : pet.getPetName());
+                setText(empty || option == null ? null : option.getLabel());
+            }
+        });
+        cbService.setButtonCell(new ListCell<>() {
+            @Override
+            protected void updateItem(DropdownOption option, boolean empty) {
+                super.updateItem(option, empty);
+                setText(empty || option == null ? null : option.getLabel());
             }
         });
 
+        cbCustomer.setCellFactory(param -> new ListCell<>() {
+            @Override
+            protected void updateItem(DropdownOption option, boolean empty) {
+                super.updateItem(option, empty);
+                setText(empty || option == null ? null : option.getLabel());
+            }
+        });
+        cbCustomer.setButtonCell(new ListCell<>() {
+            @Override
+            protected void updateItem(DropdownOption option, boolean empty) {
+                super.updateItem(option, empty);
+                setText(empty || option == null ? null : option.getLabel());
+            }
+        });
+
+        cbPet.setCellFactory(param -> new ListCell<>() {
+            @Override
+            protected void updateItem(DropdownOption option, boolean empty) {
+                super.updateItem(option, empty);
+                setText(empty || option == null ? null : option.getLabel());
+            }
+        });
         cbPet.setButtonCell(new ListCell<>() {
             @Override
-            protected void updateItem(Pet pet, boolean empty) {
+            protected void updateItem(DropdownOption option, boolean empty) {
-                super.updateItem(pet, empty);
+                super.updateItem(option, empty);
-                setText(empty || pet == null ? null : pet.getPetName());
+                setText(empty || option == null ? null : option.getLabel());
             }
         });
 
@@ -124,20 +169,20 @@ public class AppointmentDialogController {
 
         cbAppointmentStatus.setValue(appt.getAppointmentStatus());
 
-        Time time = Time.valueOf(appt.getAppointmentTime());
+        LocalTime time = LocalTime.parse(appt.getAppointmentTime());
-        cbHour.setValue(time.toLocalTime().getHour());
+        cbHour.setValue(time.getHour());
-        cbMinute.setValue(time.toLocalTime().getMinute());
+        cbMinute.setValue(time.getMinute());
 
         cbService.getItems().forEach(s -> {
-            if (s.getServiceId() == appt.getServiceId()) cbService.setValue(s);
+            if (s.getId() == appt.getServiceId()) cbService.setValue(s);
         });
 
         cbCustomer.getItems().forEach(c -> {
-            if (c.getCustomerId() == appt.getCustomerId()) cbCustomer.setValue(c);
+            if (c.getId() == appt.getCustomerId()) cbCustomer.setValue(c);
         });
 
         cbPet.getItems().forEach(p -> {
-            if (p.getPetId() == appt.getPetId()) cbPet.setValue(p);
+            if (p.getId() == appt.getPetId()) cbPet.setValue(p);
         });
     }
 
@@ -159,45 +204,40 @@ public class AppointmentDialogController {
             return;
         }
 
-        Time appointmentTime =
+        LocalTime appointmentTime = LocalTime.of(cbHour.getValue(), cbMinute.getValue());
-                Time.valueOf(String.format(
-                        "%02d:%02d:00",
-                        cbHour.getValue(),
-                        cbMinute.getValue()
-                ));
 
-        Appointment appt = new Appointment(
+        AppointmentRequest request = new AppointmentRequest();
-                selectedAppointment == null ? 0 : selectedAppointment.getAppointmentId(),
+        request.setPetIds(Collections.singletonList(cbPet.getValue().getId()));
-                cbService.getValue().getServiceId(),
+        request.setCustomerId(cbCustomer.getValue().getId());
-                cbCustomer.getValue().getCustomerId(),
+        request.setServiceId(cbService.getValue().getId());
-                dpAppointmentDate.getValue().toString(),
+        request.setAppointmentDate(dpAppointmentDate.getValue());
-                appointmentTime.toString(),
+        request.setAppointmentTime(appointmentTime);
-                cbAppointmentStatus.getValue()
+        request.setAppointmentStatus(cbAppointmentStatus.getValue());
-        );
 
+        new Thread(() -> {
             try {
-
                 if (mode.equals("Add")) {
-                int newId = AppointmentDB.insertAppointment(appt);
+                    AppointmentApi.getInstance().createAppointment(request);
-                AppointmentDB.insertAppointmentPet(newId, cbPet.getValue().getPetId());
                 } else {
-                AppointmentDB.updateAppointment(
+                    AppointmentApi.getInstance().updateAppointment(
-                        selectedAppointment.getAppointmentId(),
+                            (long) selectedAppointment.getAppointmentId(),
-                        appt,
+                            request
-                        cbPet.getValue().getPetId()
                     );
                 }
 
-            closeStage(e);
+                Platform.runLater(() -> closeStage(e));
 
             } catch (Exception ex) {
+                Platform.runLater(() -> {
                     ActivityLogger.getInstance().logException(
                         "AppointmentDialogController.buttonSaveClicked",
                         ex,
                         "Saving appointment in " + mode + " mode");
                     ex.printStackTrace();
-            showError("Error saving appointment");
+                    showError("Error saving appointment: " + ex.getMessage());
+                });
             }
+        }).start();
     }
 
     //

src/main/java/org/example/petshopdesktop/controllers/dialogcontrollers/ProductSupplierDialogController.java

@@ -1,5 +1,6 @@
 package org.example.petshopdesktop.controllers.dialogcontrollers;
 
+import javafx.application.Platform;
 import javafx.collections.FXCollections;
 import javafx.collections.ObservableList;
 import javafx.event.EventHandler;
@@ -10,16 +11,14 @@ import javafx.scene.input.MouseEvent;
 import javafx.stage.Stage;
 import org.example.petshopdesktop.DTOs.ProductSupplierDTO;
 import org.example.petshopdesktop.Validator;
-import org.example.petshopdesktop.database.ProductDB;
+import org.example.petshopdesktop.api.dto.common.DropdownOption;
-import org.example.petshopdesktop.database.ProductSupplierDB;
+import org.example.petshopdesktop.api.dto.productsupplier.ProductSupplierRequest;
-import org.example.petshopdesktop.database.SupplierDB;
+import org.example.petshopdesktop.api.dto.productsupplier.ProductSupplierResponse;
-import org.example.petshopdesktop.models.Product;
+import org.example.petshopdesktop.api.endpoints.DropdownApi;
-import org.example.petshopdesktop.models.ProductSupplier;
+import org.example.petshopdesktop.api.endpoints.ProductSupplierApi;
-import org.example.petshopdesktop.models.Supplier;
 import org.example.petshopdesktop.util.ActivityLogger;
 
-import java.sql.SQLException;
+import java.math.BigDecimal;
-import java.sql.SQLIntegrityConstraintViolationException;
 
 public class ProductSupplierDialogController {
 
@@ -30,10 +29,10 @@ public class ProductSupplierDialogController {
     private Button btnSave;
 
     @FXML
-    private ComboBox<Product> cbProduct;
+    private ComboBox<DropdownOption> cbProduct;
 
     @FXML
-    private ComboBox<Supplier> cbSupplier;
+    private ComboBox<DropdownOption> cbSupplier;
 
     @FXML
     private Label lblMode;
@@ -47,6 +46,7 @@ public class ProductSupplierDialogController {
     private String mode = null;
     private int selectedSupId = -1;
     private int selectedProdId = -1;
+    private Long selectedId = null;
 
     /**
      * add event listeners to buttons and set up combobox
@@ -67,26 +67,74 @@ public class ProductSupplierDialogController {
             }
         });
 
-        //Set up combobox for selecting product and supplier
+        cbSupplier.setButtonCell(new ListCell<DropdownOption>() {
-        try{
+            @Override
-            ObservableList<Supplier> suppliers = FXCollections.observableArrayList(); //empty list
+            protected void updateItem(DropdownOption item, boolean empty) {
-            ObservableList<Product> products = FXCollections.observableArrayList(); //empty list
+                super.updateItem(item, empty);
-
+                if (empty || item == null) {
-            //get suppliers and products from DB
+                    setText(null);
-            suppliers = SupplierDB.getSuppliers();
+                } else {
-            products = ProductDB.getProducts();
+                    setText(item.getLabel());
-
-            //Populate combobox
-            cbSupplier.setItems(suppliers);
-            cbProduct.setItems(products);
                 }
-        catch(SQLException e){
+            }
+        });
+        cbSupplier.setCellFactory(lv -> new ListCell<DropdownOption>() {
+            @Override
+            protected void updateItem(DropdownOption item, boolean empty) {
+                super.updateItem(item, empty);
+                if (empty || item == null) {
+                    setText(null);
+                } else {
+                    setText(item.getLabel());
+                }
+            }
+        });
+
+        cbProduct.setButtonCell(new ListCell<DropdownOption>() {
+            @Override
+            protected void updateItem(DropdownOption item, boolean empty) {
+                super.updateItem(item, empty);
+                if (empty || item == null) {
+                    setText(null);
+                } else {
+                    setText(item.getLabel());
+                }
+            }
+        });
+        cbProduct.setCellFactory(lv -> new ListCell<DropdownOption>() {
+            @Override
+            protected void updateItem(DropdownOption item, boolean empty) {
+                super.updateItem(item, empty);
+                if (empty || item == null) {
+                    setText(null);
+                } else {
+                    setText(item.getLabel());
+                }
+            }
+        });
+
+        new Thread(() -> {
+            try {
+                var suppliers = DropdownApi.getInstance().getSuppliers();
+                var products = DropdownApi.getInstance().getProducts();
+
+                Platform.runLater(() -> {
+                    cbSupplier.setItems(FXCollections.observableArrayList(suppliers));
+                    cbProduct.setItems(FXCollections.observableArrayList(products));
+                });
+            } catch (Exception e) {
+                Platform.runLater(() -> {
                     ActivityLogger.getInstance().logException(
                         "ProductSupplierDialogController.initialize",
                         e,
                         "Loading suppliers and products for combo boxes");
-            throw new RuntimeException(e);
+                    Alert alert = new Alert(Alert.AlertType.ERROR);
+                    alert.setHeaderText("Initialization Error");
+                    alert.setContentText("Failed to load dropdown data: " + e.getMessage());
+                    alert.showAndWait();
+                });
             }
+        }).start();
 
     }
 
@@ -96,10 +144,8 @@ public class ProductSupplierDialogController {
      * @param mouseEvent click event for save button
      */
     private void buttonSaveClicked(MouseEvent mouseEvent) {
-        int numRows = 0;
+        String errorMsg = "";
-        String errorMsg = ""; //error message for validation
 
-        //Check Validation (input required)
         errorMsg += Validator.isPresent(txtCost.getText(), "Cost");
         if (cbProduct.getSelectionModel().getSelectedItem() == null) {
             errorMsg += "Product is required \n";
@@ -108,82 +154,41 @@ public class ProductSupplierDialogController {
             errorMsg += "Supplier is required \n";
         }
 
-        //Check validation (length size)
         errorMsg += Validator.isLessThanVarChars(txtCost.getText(), "Cost", 12);
-
-        //Check validation (format)
         errorMsg += Validator.isNonNegativeDouble(txtCost.getText(), "Cost");
 
-        if(errorMsg.isEmpty()){ //no validation errors
+        if(errorMsg.isEmpty()){
-            ProductSupplier productSupplier = collectProductSupplier(); //get productSupplier info
+            ProductSupplierRequest request = collectProductSupplierRequest();
-            if (mode.equals("Add")) { //add mode
+
-                try{
+            new Thread(() -> {
-                    numRows = ProductSupplierDB.insertProductSupplier(productSupplier);
+                try {
-                }
+                    if (mode.equals("Add")) {
-                catch(SQLIntegrityConstraintViolationException e){
+                        ProductSupplierApi.getInstance().createProductSupplier(request);
-                    ActivityLogger.getInstance().logException(
+                    } else {
-                        "ProductSupplierDialogController.buttonSaveClicked",
+                        ProductSupplierApi.getInstance().updateProductSupplier(selectedId, request);
-                        e,
-                        "Inserting product-supplier (integrity constraint violation)");
-                    Alert alert = new Alert(Alert.AlertType.ERROR);
-                    alert.setHeaderText("Database Operation Error");
-                    alert.setContentText("Add failed \n" +
-                            "the product-supplier link is already in the database");
-                    alert.showAndWait();
-                    numRows = -1; //Update numRow so alert only shows once
-                    closeStage(mouseEvent);
-                }
-                catch(SQLException e){
-                    ActivityLogger.getInstance().logException(
-                        "ProductSupplierDialogController.buttonSaveClicked",
-                        e,
-                        "Inserting new product-supplier record");
-                    throw new RuntimeException(e);
-                }
-            }
-            else { //edit
-                try{
-                    numRows = ProductSupplierDB.updateProductSupplier(selectedSupId, selectedProdId, productSupplier);
-                }
-                catch(SQLIntegrityConstraintViolationException e){
-                    ActivityLogger.getInstance().logException(
-                        "ProductSupplierDialogController.buttonSaveClicked",
-                        e,
-                        "Updating product-supplier (integrity constraint violation) - SupID: " + selectedSupId + ", ProdID: " + selectedProdId);
-                    Alert alert = new Alert(Alert.AlertType.ERROR);
-                    alert.setHeaderText("Database Operation Error");
-                    alert.setContentText("Edit failed \n" +
-                            "the product-supplier link is already in the database");
-                    alert.showAndWait();
-                    numRows = -1; //Update numRow so alert only shows once
-                    closeStage(mouseEvent);
-                }
-                catch(SQLException e){
-                    ActivityLogger.getInstance().logException(
-                        "ProductSupplierDialogController.buttonSaveClicked",
-                        e,
-                        "Updating product-supplier - SupID: " + selectedSupId + ", ProdID: " + selectedProdId);
-                    throw new RuntimeException(e);
-                }
                     }
 
-            //if no rows were affected then there was an error (prompt user of error)
+                    Platform.runLater(() -> {
-            if (numRows == 0){
-                Alert alert = new Alert(Alert.AlertType.ERROR);
-                alert.setHeaderText("Database Operation Error");
-                alert.setContentText(mode + " failed");
-                alert.showAndWait();
-            }
-            else if (numRows > 0){
-                //tell the user operation was successful
                         Alert alert = new Alert(Alert.AlertType.INFORMATION);
                         alert.setHeaderText("Saved");
                         alert.setContentText(mode + " succeeded");
                         alert.showAndWait();
                         closeStage(mouseEvent);
+                    });
+                } catch (Exception e) {
+                    Platform.runLater(() -> {
+                        ActivityLogger.getInstance().logException(
+                            "ProductSupplierDialogController.buttonSaveClicked",
+                            e,
+                            mode + " product-supplier");
+                        Alert alert = new Alert(Alert.AlertType.ERROR);
+                        alert.setHeaderText("Database Operation Error");
+                        alert.setContentText(mode + " failed: " + e.getMessage());
+                        alert.showAndWait();
+                    });
                 }
-        }
+            }).start();
-        else { //Display validation errors
+        } else {
             Alert alert = new Alert(Alert.AlertType.ERROR);
             alert.setHeaderText("Input Error");
             alert.setContentText(errorMsg);
@@ -193,18 +198,14 @@ public class ProductSupplierDialogController {
 
     /**
      * collect the data for new/updated productSupplier
-     * @return productSupplier entity with data
+     * @return productSupplier request with data
      */
-    private ProductSupplier collectProductSupplier() {
+    private ProductSupplierRequest collectProductSupplierRequest() {
-        ProductSupplier productSupplier = null;
+        ProductSupplierRequest request = new ProductSupplierRequest();
-
+        request.setSupplierId(cbSupplier.getSelectionModel().getSelectedItem().getId());
-        productSupplier = new ProductSupplier(
+        request.setProductId(cbProduct.getSelectionModel().getSelectedItem().getId());
-                cbSupplier.getSelectionModel().getSelectedItem().getSupId(),
+        request.setSupplierPrice(new BigDecimal(txtCost.getText()));
-                cbProduct.getSelectionModel().getSelectedItem().getProdId(),
+        return request;
-                Double.parseDouble(txtCost.getText())
-        );
-
-        return productSupplier;
     }
 
     /**
@@ -216,20 +217,17 @@ public class ProductSupplierDialogController {
             txtCost.setText(productSupplier.getCost() + "");
         }
 
-        //Get the right combobox selection (product)
+        for (DropdownOption product : cbProduct.getItems()) {
-        for (Product product : cbProduct.getItems()) {
+            if(product.getId() == productSupplier.getProdId()){
-            if(product.getProdId() == productSupplier.getProdId()){
                 cbProduct.getSelectionModel().select(product);
             }
         }
 
-        //Get the right combobox selection (supplier)
+        for (DropdownOption supplier : cbSupplier.getItems()) {
-        for (Supplier supplier : cbSupplier.getItems()) {
+            if (supplier.getId() == productSupplier.getSupId()) {
-            if (supplier.getSupId() == productSupplier.getSupId()) {
                 cbSupplier.getSelectionModel().select(supplier);
             }
         }
-
     }
 
     /**
@@ -260,6 +258,7 @@ public class ProductSupplierDialogController {
     public void setSelectedIds(int supId, int prodId){
         this.selectedSupId = supId;
         this.selectedProdId = prodId;
+        this.selectedId = (long) supId;
     }
 
 }

src/main/java/org/example/petshopdesktop/controllers/dialogcontrollers/RefundDialogController.java

@@ -7,15 +7,19 @@ import javafx.fxml.FXML;
 import javafx.scene.control.*;
 import javafx.scene.control.cell.PropertyValueFactory;
 import javafx.stage.Stage;
+import org.example.petshopdesktop.api.dto.sale.SaleItemRequest;
+import org.example.petshopdesktop.api.dto.sale.SaleItemResponse;
+import org.example.petshopdesktop.api.dto.sale.SaleRequest;
+import org.example.petshopdesktop.api.dto.sale.SaleResponse;
+import org.example.petshopdesktop.api.endpoints.SaleApi;
 import org.example.petshopdesktop.auth.UserSession;
-import org.example.petshopdesktop.database.SaleDB;
-import org.example.petshopdesktop.models.SaleCartItem;
-import org.example.petshopdesktop.models.SaleDetail;
 import org.example.petshopdesktop.util.ActivityLogger;
 
-import java.sql.SQLException;
+import java.math.BigDecimal;
 import java.text.NumberFormat;
 import java.time.format.DateTimeFormatter;
+import java.util.ArrayList;
+import java.util.List;
 import java.util.Locale;
 import java.util.Optional;
 
@@ -31,19 +35,19 @@ public class RefundDialogController {
     private Label lblSaleInfo;
 
     @FXML
-    private TableView<SaleDetail.SaleDetailItem> tvOriginalItems;
+    private TableView<SaleItemResponse> tvOriginalItems;
 
     @FXML
-    private TableColumn<SaleDetail.SaleDetailItem, String> colOriginalProduct;
+    private TableColumn<SaleItemResponse, String> colOriginalProduct;
 
     @FXML
-    private TableColumn<SaleDetail.SaleDetailItem, Integer> colOriginalQuantity;
+    private TableColumn<SaleItemResponse, Integer> colOriginalQuantity;
 
     @FXML
-    private TableColumn<SaleDetail.SaleDetailItem, Double> colOriginalUnitPrice;
+    private TableColumn<SaleItemResponse, BigDecimal> colOriginalUnitPrice;
 
     @FXML
-    private TableColumn<SaleDetail.SaleDetailItem, Double> colOriginalTotal;
+    private TableColumn<SaleItemResponse, BigDecimal> colOriginalTotal;
 
     @FXML
     private Button btnAddToRefund;
@@ -78,7 +82,7 @@ public class RefundDialogController {
     @FXML
     private Button btnCancel;
 
-    private SaleDetail currentSale;
+    private SaleResponse currentSale;
     private final ObservableList<RefundItem> refundItems = FXCollections.observableArrayList();
     private final NumberFormat currency = NumberFormat.getCurrencyInstance(Locale.CANADA);
 
@@ -94,7 +98,7 @@ public class RefundDialogController {
         colOriginalProduct.setCellValueFactory(new PropertyValueFactory<>("productName"));
         colOriginalQuantity.setCellValueFactory(new PropertyValueFactory<>("quantity"));
         colOriginalUnitPrice.setCellValueFactory(new PropertyValueFactory<>("unitPrice"));
-        colOriginalTotal.setCellValueFactory(new PropertyValueFactory<>("total"));
+        colOriginalTotal.setCellValueFactory(new PropertyValueFactory<>("lineTotal"));
         tvOriginalItems.getSelectionModel().setSelectionMode(SelectionMode.SINGLE);
 
         colRefundProduct.setCellValueFactory(new PropertyValueFactory<>("productName"));
@@ -113,21 +117,25 @@ public class RefundDialogController {
             return;
         }
 
-        int saleId;
+        Long saleId;
         try {
-            saleId = Integer.parseInt(saleIdText);
+            saleId = Long.parseLong(saleIdText);
         } catch (NumberFormatException e) {
             showError("Load Sale", "Invalid transaction ID.");
             return;
         }
 
         try {
-            if (SaleDB.isRefunded(saleId)) {
+            List<SaleResponse> allSales = SaleApi.getInstance().listSales(0, 1000, null);
+            boolean alreadyRefunded = allSales.stream()
+                .anyMatch(s -> Boolean.TRUE.equals(s.getIsRefund()) && saleId.equals(s.getOriginalSaleId()));
+
+            if (alreadyRefunded) {
                 showError("Load Sale", "This sale has already been refunded.");
                 return;
             }
 
-            currentSale = SaleDB.getSaleById(saleId);
+            currentSale = SaleApi.getInstance().getSale(saleId);
 
             DateTimeFormatter formatter = DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm");
             String saleInfo = String.format("Sale Date: %s | Employee: %s | Original Total: %s | Payment: %s",
@@ -137,13 +145,13 @@ public class RefundDialogController {
                 currentSale.getPaymentMethod());
             lblSaleInfo.setText(saleInfo);
 
-            tvOriginalItems.setItems(currentSale.getItems());
+            tvOriginalItems.setItems(FXCollections.observableArrayList(currentSale.getItems()));
             cbPaymentMethod.getSelectionModel().select(currentSale.getPaymentMethod());
 
             refundItems.clear();
             updateRefundTotal();
 
-        } catch (SQLException e) {
+        } catch (Exception e) {
             ActivityLogger.getInstance().logException("RefundDialogController.btnLoadSaleClicked", e, "Loading sale");
             showError("Load Sale", e.getMessage() != null ? e.getMessage() : "Could not load sale.");
         }
@@ -156,14 +164,14 @@ public class RefundDialogController {
             return;
         }
 
-        SaleDetail.SaleDetailItem selected = tvOriginalItems.getSelectionModel().getSelectedItem();
+        SaleItemResponse selected = tvOriginalItems.getSelectionModel().getSelectedItem();
         if (selected == null) {
             showError("Add to Refund", "Select an item from the original sale.");
             return;
         }
 
         int alreadyRefunded = refundItems.stream()
-            .filter(r -> r.getProdId() == selected.getProdId())
+            .filter(r -> r.getProductId().equals(selected.getId()))
             .mapToInt(RefundItem::getQuantity)
             .sum();
 
@@ -192,7 +200,7 @@ public class RefundDialogController {
                 }
 
                 refundItems.add(new RefundItem(
-                    selected.getProdId(),
+                    selected.getId(),
                     selected.getProductName(),
                     quantity,
                     selected.getUnitPrice()
@@ -226,9 +234,9 @@ public class RefundDialogController {
             return;
         }
 
-        Integer employeeId = UserSession.getInstance().getEmployeeId();
+        Long storeId = UserSession.getInstance().getStoreId();
-        if (employeeId == null || employeeId <= 0) {
+        if (storeId == null || storeId <= 0) {
-            showError("Process Refund", "Employee is not set for this account.");
+            showError("Process Refund", "Store is not set for this account.");
             return;
         }
 
@@ -240,7 +248,7 @@ public class RefundDialogController {
 
         Alert confirm = new Alert(Alert.AlertType.CONFIRMATION);
         confirm.setTitle("Confirm Refund");
-        confirm.setHeaderText("Process refund for sale ID " + currentSale.getSaleId() + "?");
+        confirm.setHeaderText("Process refund for sale ID " + currentSale.getId() + "?");
         confirm.setContentText("Refund amount: " + lblRefundTotal.getText());
 
         Optional<ButtonType> confirmResult = confirm.showAndWait();
@@ -249,22 +257,33 @@ public class RefundDialogController {
         }
 
         try {
-            ObservableList<SaleCartItem> cartItems = FXCollections.observableArrayList();
+            SaleRequest request = new SaleRequest();
-            for (RefundItem item : refundItems) {
+            request.setStoreId(storeId);
-                cartItems.add(new SaleCartItem(item.getProdId(), item.getProductName(), item.getQuantity(), item.getUnitPrice()));
+            request.setPaymentMethod(payment);
-            }
+            request.setIsRefund(true);
+            request.setOriginalSaleId(currentSale.getId());
 
-            int refundId = SaleDB.createRefund(currentSale.getSaleId(), employeeId, payment, cartItems);
+            List<SaleItemRequest> items = new ArrayList<>();
+            for (RefundItem item : refundItems) {
+                SaleItemRequest saleItem = new SaleItemRequest();
+                saleItem.setProductId(item.getProductId());
+                saleItem.setQuantity(-item.getQuantity());
+                saleItem.setUnitPrice(item.getUnitPrice());
+                items.add(saleItem);
+            }
+            request.setItems(items);
+
+            SaleResponse refundResponse = SaleApi.getInstance().createSale(request);
 
             Alert success = new Alert(Alert.AlertType.INFORMATION);
             success.setTitle("Refund Processed");
             success.setHeaderText(null);
-            success.setContentText("Refund ID " + refundId + " was created successfully.");
+            success.setContentText("Refund ID " + refundResponse.getId() + " was created successfully.");
             success.showAndWait();
 
             closeDialog();
 
-        } catch (SQLException e) {
+        } catch (Exception e) {
             ActivityLogger.getInstance().logException("RefundDialogController.btnProcessRefundClicked", e, "Processing refund");
             showError("Process Refund", e.getMessage() != null ? e.getMessage() : "Could not process refund.");
         }

src/main/java/org/example/petshopdesktop/controllers/dialogcontrollers/ServiceDialogController.java

@@ -1,18 +1,19 @@
 package org.example.petshopdesktop.controllers.dialogcontrollers;
 
-
+import javafx.application.Platform;
 import javafx.fxml.FXML;
-import javafx.scene.Node;
+import javafx.scene.control.Alert;
 import javafx.scene.control.Button;
+import javafx.scene.control.ComboBox;
 import javafx.scene.control.Label;
 import javafx.scene.control.TextField;
-import javafx.scene.input.MouseEvent;
 import javafx.stage.Stage;
-import org.example.petshopdesktop.database.ServiceDB;
+import org.example.petshopdesktop.DTOs.ServiceDTO;
-import org.example.petshopdesktop.models.Service;
+import org.example.petshopdesktop.api.dto.service.ServiceRequest;
+import org.example.petshopdesktop.api.endpoints.ServiceApi;
 import org.example.petshopdesktop.util.ActivityLogger;
-import javafx.scene.control.Alert;
+
-import javafx.scene.control.ComboBox;
+import java.math.BigDecimal;
 
 
 public class ServiceDialogController {
@@ -45,7 +46,7 @@ public class ServiceDialogController {
     private ComboBox<Integer> cbMinutes;
 
     private String mode;
-    private Service selectedService;
+    private ServiceDTO selectedService;
 
 
 
@@ -68,7 +69,7 @@ public class ServiceDialogController {
         }
     }
 
-    public void setService(Service service) {
+    public void setService(ServiceDTO service) {
         this.selectedService = service;
 
         lblServiceId.setText("ID: " + service.getServiceId());

src/main/java/org/example/petshopdesktop/controllers/dialogcontrollers/StaffRegisterDialogController.java

@@ -1,5 +1,6 @@
 package org.example.petshopdesktop.controllers.dialogcontrollers;
 
+import javafx.application.Platform;
 import javafx.event.ActionEvent;
 import javafx.fxml.FXML;
 import javafx.scene.control.Alert;
@@ -8,11 +9,10 @@ import javafx.scene.control.Label;
 import javafx.scene.control.PasswordField;
 import javafx.scene.control.TextField;
 import javafx.stage.Stage;
-import org.example.petshopdesktop.database.UserDB;
+import org.example.petshopdesktop.api.dto.user.UserRequest;
+import org.example.petshopdesktop.api.endpoints.UserApi;
 import org.example.petshopdesktop.util.ActivityLogger;
 
-import java.sql.SQLException;
-
 public class StaffRegisterDialogController {
 
     @FXML
@@ -48,8 +48,6 @@ public class StaffRegisterDialogController {
 
         String firstName = value(txtFirstName);
         String lastName = value(txtLastName);
-        String email = value(txtEmail);
-        String phone = value(txtPhone);
         String username = value(txtUsername);
         String password = txtPassword.getText() == null ? "" : txtPassword.getText();
         String confirm = txtPasswordConfirm.getText() == null ? "" : txtPasswordConfirm.getText();
@@ -58,14 +56,6 @@ public class StaffRegisterDialogController {
             lblError.setText("First name and last name are required.");
             return;
         }
-        if (email.isBlank()) {
-            lblError.setText("Email is required.");
-            return;
-        }
-        if (phone.isBlank()) {
-            lblError.setText("Phone is required.");
-            return;
-        }
         if (username.isBlank()) {
             lblError.setText("Username is required.");
             return;
@@ -79,26 +69,41 @@ public class StaffRegisterDialogController {
             return;
         }
 
+        btnCreate.setDisable(true);
+
+        new Thread(() -> {
             try {
-            UserDB.createStaffAccount(firstName, lastName, email, phone, username, password);
+                UserRequest request = new UserRequest();
+                request.setUsername(username);
+                request.setPassword(password);
+                request.setFirstName(firstName);
+                request.setLastName(lastName);
+                request.setRole("STAFF");
+                request.setActive(true);
+
+                UserApi.getInstance().createUser(request);
+
+                Platform.runLater(() -> {
                     Alert alert = new Alert(Alert.AlertType.INFORMATION);
                     alert.setTitle("Staff Account");
                     alert.setHeaderText(null);
                     alert.setContentText("Staff account created. You can log in now.");
                     alert.showAndWait();
                     close();
-        } catch (SQLException e) {
+                });
+            } catch (Exception e) {
                 ActivityLogger.getInstance().logException("StaffRegisterDialogController.btnCreateClicked", e, "Creating staff account");
                 String msg = e.getMessage() == null ? "Could not create staff account." : e.getMessage();
+                Platform.runLater(() -> {
                     if (msg.toLowerCase().contains("duplicate") || msg.toLowerCase().contains("unique")) {
                         lblError.setText("Username already exists.");
                     } else {
                         lblError.setText(msg);
                     }
-        } catch (RuntimeException e) {
+                    btnCreate.setDisable(false);
-            ActivityLogger.getInstance().logException("StaffRegisterDialogController.btnCreateClicked", e, "Database connection");
+                });
-            lblError.setText("Database is not connected.");
             }
+        }).start();
     }
 
     @FXML

src/main/java/org/example/petshopdesktop/controllers/dialogcontrollers/SupplierDialogController.java

@@ -10,12 +10,12 @@ import javafx.scene.control.TextField;
 import javafx.scene.input.MouseEvent;
 import javafx.stage.Stage;
 import org.example.petshopdesktop.Validator;
-import org.example.petshopdesktop.database.SupplierDB;
+import org.example.petshopdesktop.api.dto.supplier.SupplierRequest;
+import org.example.petshopdesktop.api.dto.supplier.SupplierResponse;
+import org.example.petshopdesktop.api.endpoints.SupplierApi;
 import org.example.petshopdesktop.models.Supplier;
 import org.example.petshopdesktop.util.ActivityLogger;
 
-import java.sql.SQLException;
-
 public class SupplierDialogController {
 
     @FXML
@@ -74,7 +74,6 @@ public class SupplierDialogController {
      * @param mouseEvent click event for save button
      */
     private void buttonSaveClicked(MouseEvent mouseEvent) {
-        int numRow = 0; //how many rows affected
         String errorMsg = ""; //error message for validation
 
         //Check validation (input required)
@@ -95,44 +94,29 @@ public class SupplierDialogController {
         errorMsg += Validator.isValidPhoneNumber(txtPhone.getText(), "Phone Number");
 
         if(errorMsg.isEmpty()){ //no validation errors detected
-            Supplier supplier = collectSupplier(); //get supplier info
+            SupplierRequest request = createSupplierRequest();
-            if (mode.equals("Add")) { //add mode
+            try {
-                try{
+                if (mode.equals("Add")) {
-                    numRow = SupplierDB.insertSupplier(supplier);
+                    SupplierApi.getInstance().createSupplier(request);
-                } catch (SQLException e) {
+                } else {
-                    ActivityLogger.getInstance().logException(
+                    Long supplierId = Long.parseLong(lblSupId.getText().split(": ")[1]);
-                        "SupplierDialogController.buttonSaveClicked",
+                    SupplierApi.getInstance().updateSupplier(supplierId, request);
-                        e,
-                        "Inserting new supplier record");
-                    throw new RuntimeException(e);
-                }
-            }
-            else{ //edit mode
-                try{
-                    numRow = SupplierDB.updateSupplier(supplier.getSupId(),supplier);
-                } catch (SQLException e) {
-                    ActivityLogger.getInstance().logException(
-                        "SupplierDialogController.buttonSaveClicked",
-                        e,
-                        "Updating supplier with ID: " + supplier.getSupId());
-                    throw new RuntimeException(e);
-                }
                 }
 
-            //if no rows were affected then there was an error (prompt user of error)
-            if (numRow == 0){
-                Alert alert = new Alert(Alert.AlertType.ERROR);
-                alert.setHeaderText("Database Operation Error");
-                alert.setContentText(mode + " failed");
-                alert.showAndWait();
-            }
-            else {
-                //tell the user operation was successful
                 Alert alert = new Alert(Alert.AlertType.INFORMATION);
                 alert.setHeaderText("Saved");
                 alert.setContentText(mode + " succeeded");
                 alert.showAndWait();
                 closeStage(mouseEvent);
+            } catch (Exception e) {
+                ActivityLogger.getInstance().logException(
+                    "SupplierDialogController.buttonSaveClicked",
+                    e,
+                    mode.equals("Add") ? "Inserting new supplier record" : "Updating supplier record");
+                Alert alert = new Alert(Alert.AlertType.ERROR);
+                alert.setHeaderText("Database Operation Error");
+                alert.setContentText(mode + " failed: " + e.getMessage());
+                alert.showAndWait();
             }
         }
         else{ //Display validation errors
@@ -154,26 +138,16 @@ public class SupplierDialogController {
     }
 
     /**
-     * Collect the supplier info
+     * Create a supplier request from the form inputs
-     * @return supplier info with the id or the new supplier
+     * @return supplier request for API call
      */
-    private Supplier collectSupplier(){
+    private SupplierRequest createSupplierRequest(){
-        int supId = 0;
+        SupplierRequest request = new SupplierRequest();
-        Supplier supplier = null;
+        request.setSupplierName(txtCompanyName.getText());
-
+        request.setContactPerson(txtContactFirstName.getText() + " " + txtContactLastName.getText());
-        if(lblSupId.isVisible()){ //Edit mode
+        request.setEmail(txtEmail.getText());
-            //get supplier id from lblId (split the string so we only get the int)
+        request.setPhone(txtPhone.getText());
-            supId = Integer.parseInt(lblSupId.getText().split(": ")[1]);
+        return request;
-        }
-        supplier = new Supplier(
-                supId,
-                txtCompanyName.getText(),
-                txtContactFirstName.getText(),
-                txtContactLastName.getText(),
-                txtEmail.getText(),
-                txtPhone.getText()
-        );
-        return supplier;
     }
 
     /**

src/main/java/org/example/petshopdesktop/models/Adoption.java

@@ -8,16 +8,17 @@ public class Adoption {
     private SimpleIntegerProperty adoptionId;
     private SimpleIntegerProperty petId;
     private SimpleIntegerProperty customerId;
+    private SimpleStringProperty petName;
     private SimpleStringProperty customerName;
     private SimpleStringProperty adoptionDate;
     private SimpleDoubleProperty adoptionFee;
     private SimpleStringProperty adoptionStatus;
 
-    //Constructor
+    public Adoption(int adoptionId, int petId, int customerId, String petName, String customerName, String adoptionDate, double adoptionFee, String adoptionStatus) {
-    public Adoption(int adoptionId, int petId, int customerId, String customerName, String adoptionDate, double adoptionFee, String adoptionStatus) {
         this.adoptionId = new SimpleIntegerProperty(adoptionId);
         this.petId = new SimpleIntegerProperty(petId);
         this.customerId = new SimpleIntegerProperty(customerId);
+        this.petName = new SimpleStringProperty(petName);
         this.customerName = new SimpleStringProperty(customerName);
         this.adoptionDate = new SimpleStringProperty(adoptionDate);
         this.adoptionFee = new SimpleDoubleProperty(adoptionFee);
@@ -42,6 +43,12 @@ public class Adoption {
 
     public SimpleIntegerProperty customerIdProperty() { return customerId; }
 
+    public String getPetName() { return petName.get(); }
+
+    public void setPetName(String petName) { this.petName.set(petName); }
+
+    public SimpleStringProperty petNameProperty() { return petName; }
+
     public String getCustomerName() { return customerName.get(); }
 
     public void setCustomerName(String customerName) { this.customerName.set(customerName); }

src/main/java/org/example/petshopdesktop/models/Inventory.java

@@ -7,14 +7,21 @@ public class Inventory {
     private SimpleIntegerProperty inventoryId;
     private SimpleIntegerProperty prodId;
     private SimpleStringProperty prodName;
+    private SimpleStringProperty categoryName;
+    private SimpleIntegerProperty storeId;
+    private SimpleStringProperty storeName;
     private SimpleIntegerProperty quantity;
+    private SimpleIntegerProperty reorderLevel;
 
-    //Constructor
+    public Inventory(int inventoryId, int prodId, String prodName, String categoryName, int storeId, String storeName, int quantity, int reorderLevel) {
-    public Inventory(int inventoryId, int prodId, String prodName, int quantity) {
         this.inventoryId = new SimpleIntegerProperty(inventoryId);
         this.prodId = new SimpleIntegerProperty(prodId);
         this.prodName = new SimpleStringProperty(prodName);
+        this.categoryName = new SimpleStringProperty(categoryName);
+        this.storeId = new SimpleIntegerProperty(storeId);
+        this.storeName = new SimpleStringProperty(storeName);
         this.quantity = new SimpleIntegerProperty(quantity);
+        this.reorderLevel = new SimpleIntegerProperty(reorderLevel);
     }
 
     public int getInventoryId() { return inventoryId.get(); }
@@ -35,9 +42,33 @@ public class Inventory {
 
     public SimpleStringProperty prodNameProperty() { return prodName; }
 
+    public String getCategoryName() { return categoryName.get(); }
+
+    public void setCategoryName(String categoryName) { this.categoryName.set(categoryName); }
+
+    public SimpleStringProperty categoryNameProperty() { return categoryName; }
+
+    public int getStoreId() { return storeId.get(); }
+
+    public void setStoreId(int storeId) { this.storeId.set(storeId); }
+
+    public SimpleIntegerProperty storeIdProperty() { return storeId; }
+
+    public String getStoreName() { return storeName.get(); }
+
+    public void setStoreName(String storeName) { this.storeName.set(storeName); }
+
+    public SimpleStringProperty storeNameProperty() { return storeName; }
+
     public int getQuantity() { return quantity.get(); }
 
     public void setQuantity(int quantity) { this.quantity.set(quantity); }
 
     public SimpleIntegerProperty quantityProperty() { return quantity; }
+
+    public int getReorderLevel() { return reorderLevel.get(); }
+
+    public void setReorderLevel(int reorderLevel) { this.reorderLevel.set(reorderLevel); }
+
+    public SimpleIntegerProperty reorderLevelProperty() { return reorderLevel; }
 }

src/main/java/org/example/petshopdesktop/models/PurchaseOrder.java

@@ -1,35 +1,52 @@
 package org.example.petshopdesktop.models;
 
+import java.math.BigDecimal;
+import java.time.LocalDate;
+
 public class PurchaseOrder {
 
-    private int purchaseOrderId;
+    private long purchaseOrderId;
-    private int supId;
+    private String supplierName;
-    private String orderDate;
+    private LocalDate orderDate;
+    private LocalDate expectedDeliveryDate;
     private String status;
+    private BigDecimal totalAmount;
 
-    public PurchaseOrder(int purchaseOrderId,
+    public PurchaseOrder(long purchaseOrderId,
-                         int supId,
+                         String supplierName,
-                         String orderDate,
+                         LocalDate orderDate,
-                         String status) {
+                         LocalDate expectedDeliveryDate,
+                         String status,
+                         BigDecimal totalAmount) {
         this.purchaseOrderId = purchaseOrderId;
-        this.supId = supId;
+        this.supplierName = supplierName;
         this.orderDate = orderDate;
+        this.expectedDeliveryDate = expectedDeliveryDate;
         this.status = status;
+        this.totalAmount = totalAmount;
     }
 
-    public int getPurchaseOrderId() {
+    public long getPurchaseOrderId() {
         return purchaseOrderId;
     }
 
-    public int getSupId() {
+    public String getSupplierName() {
-        return supId;
+        return supplierName;
     }
 
-    public String getOrderDate() {
+    public LocalDate getOrderDate() {
         return orderDate;
     }
 
+    public LocalDate getExpectedDeliveryDate() {
+        return expectedDeliveryDate;
+    }
+
     public String getStatus() {
         return status;
     }
+
+    public BigDecimal getTotalAmount() {
+        return totalAmount;
+    }
 }

src/main/java/org/example/petshopdesktop/models/StaffAccount.java

@@ -3,8 +3,8 @@ package org.example.petshopdesktop.models;
 import java.sql.Timestamp;
 
 public class StaffAccount {
-    private final int userId;
+    private final long userId;
-    private final int employeeId;
+    private final long employeeId;
     private final String username;
     private final String firstName;
     private final String lastName;
@@ -13,7 +13,7 @@ public class StaffAccount {
     private final boolean active;
     private final Timestamp createdAt;
 
-    public StaffAccount(int userId, int employeeId, String username, String firstName, String lastName, String email, String phone, boolean active, Timestamp createdAt) {
+    public StaffAccount(long userId, long employeeId, String username, String firstName, String lastName, String email, String phone, boolean active, Timestamp createdAt) {
         this.userId = userId;
         this.employeeId = employeeId;
         this.username = username;
@@ -25,11 +25,11 @@ public class StaffAccount {
         this.createdAt = createdAt;
     }
 
-    public int getUserId() {
+    public long getUserId() {
         return userId;
     }
 
-    public int getEmployeeId() {
+    public long getEmployeeId() {
         return employeeId;
     }