Fix null pointers and unsafe parsing bugs

src/main/java/org/example/petshopdesktop/api/ApiClient.java

@@ -44,6 +44,28 @@ public class ApiClient {
         return handleResponse(response, responseClass);
     }
 
+    public String getRawResponse(String path) throws Exception {
+        HttpRequest.Builder builder = HttpRequest.newBuilder()
+                .uri(URI.create(baseUrl + path))
+                .GET()
+                .timeout(Duration.ofSeconds(30));
+
+        addAuthHeader(builder);
+
+        HttpRequest request = builder.build();
+        HttpResponse<String> response = httpClient.send(request, HttpResponse.BodyHandlers.ofString());
+
+        if (response.statusCode() == 200 || response.statusCode() == 201) {
+            return response.body();
+        } else if (response.statusCode() == 401) {
+            throw new RuntimeException("Authentication failed. Please log in again.");
+        } else if (response.statusCode() == 403) {
+            throw new RuntimeException("Access restricted. You don't have permission to perform this action.");
+        } else {
+            throw new RuntimeException(parseErrorMessage(response));
+        }
+    }
+
     public <T> T post(String path, Object requestBody, Class<T> responseClass) throws Exception {
         String jsonBody = objectMapper.writeValueAsString(requestBody);
 
@@ -155,6 +177,7 @@ public class ApiClient {
                 }
             }
         } catch (Exception e) {
+            System.err.println("Error parsing error message: " + e.getMessage());
         }
         return "Request failed with status " + response.statusCode();
     }

src/main/java/org/example/petshopdesktop/api/endpoints/AdoptionApi.java

@@ -5,7 +5,10 @@ import org.example.petshopdesktop.api.ApiClient;
 import org.example.petshopdesktop.api.dto.adoption.AdoptionRequest;
 import org.example.petshopdesktop.api.dto.adoption.AdoptionResponse;
 import org.example.petshopdesktop.api.dto.common.BulkDeleteRequest;
+import org.example.petshopdesktop.api.dto.common.PageResponse;
 
+import java.net.URLEncoder;
+import java.nio.charset.StandardCharsets;
 import java.util.List;
 
 public class AdoptionApi {
@@ -23,10 +26,17 @@ public class AdoptionApi {
     public List<AdoptionResponse> listAdoptions(String query) throws Exception {
         String path = "/api/v1/adoptions?page=0&size=1000";
         if (query != null && !query.isEmpty()) {
-            path += "&q=" + query;
+            path += "&q=" + URLEncoder.encode(query, StandardCharsets.UTF_8);
         }
-        String response = apiClient.get(path, String.class);
+        String response = apiClient.getRawResponse(path);
-        return apiClient.getObjectMapper().readValue(response, new TypeReference<List<AdoptionResponse>>() {});
+        PageResponse<AdoptionResponse> pageResponse = apiClient.getObjectMapper().readValue(
+            response,
+            new TypeReference<PageResponse<AdoptionResponse>>() {}
+        );
+        if (pageResponse == null) {
+            throw new IllegalStateException("Null response from adoptions endpoint");
+        }
+        return pageResponse.getContent();
     }
 
     public AdoptionResponse createAdoption(AdoptionRequest request) throws Exception {

src/main/java/org/example/petshopdesktop/api/endpoints/AppointmentApi.java

@@ -5,7 +5,10 @@ import org.example.petshopdesktop.api.ApiClient;
 import org.example.petshopdesktop.api.dto.appointment.AppointmentRequest;
 import org.example.petshopdesktop.api.dto.appointment.AppointmentResponse;
 import org.example.petshopdesktop.api.dto.common.BulkDeleteRequest;
+import org.example.petshopdesktop.api.dto.common.PageResponse;
 
+import java.net.URLEncoder;
+import java.nio.charset.StandardCharsets;
 import java.util.List;
 
 public class AppointmentApi {
@@ -23,10 +26,17 @@ public class AppointmentApi {
     public List<AppointmentResponse> listAppointments(String query) throws Exception {
         String path = "/api/v1/appointments?page=0&size=1000";
         if (query != null && !query.isEmpty()) {
-            path += "&q=" + query;
+            path += "&q=" + URLEncoder.encode(query, StandardCharsets.UTF_8);
         }
-        String response = apiClient.get(path, String.class);
+        String response = apiClient.getRawResponse(path);
-        return apiClient.getObjectMapper().readValue(response, new TypeReference<List<AppointmentResponse>>() {});
+        PageResponse<AppointmentResponse> pageResponse = apiClient.getObjectMapper().readValue(
+            response,
+            new TypeReference<PageResponse<AppointmentResponse>>() {}
+        );
+        if (pageResponse == null) {
+            throw new IllegalStateException("Null response from appointments endpoint");
+        }
+        return pageResponse.getContent();
     }
 
     public AppointmentResponse createAppointment(AppointmentRequest request) throws Exception {

src/main/java/org/example/petshopdesktop/api/endpoints/DropdownApi.java

@@ -19,37 +19,58 @@ public class DropdownApi {
     }
 
     public List<DropdownOption> getCategories() throws Exception {
-        String response = apiClient.get("/api/v1/dropdowns/categories", String.class);
+        String response = apiClient.getRawResponse("/api/v1/dropdowns/categories");
+        if (response == null || response.isEmpty()) {
+            throw new IllegalStateException("Empty response from categories endpoint");
+        }
         return apiClient.getObjectMapper().readValue(response, new TypeReference<List<DropdownOption>>() {});
     }
 
     public List<DropdownOption> getProducts() throws Exception {
-        String response = apiClient.get("/api/v1/dropdowns/products", String.class);
+        String response = apiClient.getRawResponse("/api/v1/dropdowns/products");
+        if (response == null || response.isEmpty()) {
+            throw new IllegalStateException("Empty response from products endpoint");
+        }
         return apiClient.getObjectMapper().readValue(response, new TypeReference<List<DropdownOption>>() {});
     }
 
     public List<DropdownOption> getSuppliers() throws Exception {
-        String response = apiClient.get("/api/v1/dropdowns/suppliers", String.class);
+        String response = apiClient.getRawResponse("/api/v1/dropdowns/suppliers");
+        if (response == null || response.isEmpty()) {
+            throw new IllegalStateException("Empty response from suppliers endpoint");
+        }
         return apiClient.getObjectMapper().readValue(response, new TypeReference<List<DropdownOption>>() {});
     }
 
     public List<DropdownOption> getServices() throws Exception {
-        String response = apiClient.get("/api/v1/dropdowns/services", String.class);
+        String response = apiClient.getRawResponse("/api/v1/dropdowns/services");
+        if (response == null || response.isEmpty()) {
+            throw new IllegalStateException("Empty response from services endpoint");
+        }
         return apiClient.getObjectMapper().readValue(response, new TypeReference<List<DropdownOption>>() {});
     }
 
     public List<DropdownOption> getCustomers() throws Exception {
-        String response = apiClient.get("/api/v1/dropdowns/customers", String.class);
+        String response = apiClient.getRawResponse("/api/v1/dropdowns/customers");
+        if (response == null || response.isEmpty()) {
+            throw new IllegalStateException("Empty response from customers endpoint");
+        }
         return apiClient.getObjectMapper().readValue(response, new TypeReference<List<DropdownOption>>() {});
     }
 
     public List<DropdownOption> getPets() throws Exception {
-        String response = apiClient.get("/api/v1/dropdowns/pets", String.class);
+        String response = apiClient.getRawResponse("/api/v1/dropdowns/pets");
+        if (response == null || response.isEmpty()) {
+            throw new IllegalStateException("Empty response from pets endpoint");
+        }
         return apiClient.getObjectMapper().readValue(response, new TypeReference<List<DropdownOption>>() {});
     }
 
     public List<DropdownOption> getStores() throws Exception {
-        String response = apiClient.get("/api/v1/dropdowns/stores", String.class);
+        String response = apiClient.getRawResponse("/api/v1/dropdowns/stores");
+        if (response == null || response.isEmpty()) {
+            throw new IllegalStateException("Empty response from stores endpoint");
+        }
         return apiClient.getObjectMapper().readValue(response, new TypeReference<List<DropdownOption>>() {});
     }
 }

src/main/java/org/example/petshopdesktop/api/endpoints/InventoryApi.java

@@ -2,9 +2,12 @@ package org.example.petshopdesktop.api.endpoints;
 
 import com.fasterxml.jackson.core.type.TypeReference;
 import org.example.petshopdesktop.api.ApiClient;
+import org.example.petshopdesktop.api.dto.common.PageResponse;
 import org.example.petshopdesktop.api.dto.inventory.InventoryRequest;
 import org.example.petshopdesktop.api.dto.inventory.InventoryResponse;
 
+import java.net.URLEncoder;
+import java.nio.charset.StandardCharsets;
 import java.util.List;
 
 public class InventoryApi {
@@ -22,10 +25,17 @@ public class InventoryApi {
     public List<InventoryResponse> listInventory(String query) throws Exception {
         String path = "/api/v1/inventory?page=0&size=1000";
         if (query != null && !query.isEmpty()) {
-            path += "&q=" + query;
+            path += "&q=" + URLEncoder.encode(query, StandardCharsets.UTF_8);
         }
-        String response = apiClient.get(path, String.class);
+        String response = apiClient.getRawResponse(path);
-        return apiClient.getObjectMapper().readValue(response, new TypeReference<List<InventoryResponse>>() {});
+        PageResponse<InventoryResponse> pageResponse = apiClient.getObjectMapper().readValue(
+            response,
+            new TypeReference<PageResponse<InventoryResponse>>() {}
+        );
+        if (pageResponse == null) {
+            throw new IllegalStateException("Null response from inventory endpoint");
+        }
+        return pageResponse.getContent();
     }
 
     public InventoryResponse createInventory(InventoryRequest request) throws Exception {

src/main/java/org/example/petshopdesktop/api/endpoints/PetApi.java

@@ -3,9 +3,12 @@ package org.example.petshopdesktop.api.endpoints;
 import com.fasterxml.jackson.core.type.TypeReference;
 import org.example.petshopdesktop.api.ApiClient;
 import org.example.petshopdesktop.api.dto.common.BulkDeleteRequest;
+import org.example.petshopdesktop.api.dto.common.PageResponse;
 import org.example.petshopdesktop.api.dto.pet.PetRequest;
 import org.example.petshopdesktop.api.dto.pet.PetResponse;
 
+import java.net.URLEncoder;
+import java.nio.charset.StandardCharsets;
 import java.util.List;
 
 public class PetApi {
@@ -23,10 +26,17 @@ public class PetApi {
     public List<PetResponse> listPets(String query) throws Exception {
         String path = "/api/v1/pets?page=0&size=1000";
         if (query != null && !query.isEmpty()) {
-            path += "&q=" + query;
+            path += "&q=" + URLEncoder.encode(query, StandardCharsets.UTF_8);
         }
-        String response = apiClient.get(path, String.class);
+        String response = apiClient.getRawResponse(path);
-        return apiClient.getObjectMapper().readValue(response, new TypeReference<List<PetResponse>>() {});
+        PageResponse<PetResponse> pageResponse = apiClient.getObjectMapper().readValue(
+            response,
+            new TypeReference<PageResponse<PetResponse>>() {}
+        );
+        if (pageResponse == null) {
+            throw new IllegalStateException("Null response from pets endpoint");
+        }
+        return pageResponse.getContent();
     }
 
     public PetResponse createPet(PetRequest request) throws Exception {

src/main/java/org/example/petshopdesktop/api/endpoints/ProductApi.java

@@ -3,9 +3,12 @@ package org.example.petshopdesktop.api.endpoints;
 import com.fasterxml.jackson.core.type.TypeReference;
 import org.example.petshopdesktop.api.ApiClient;
 import org.example.petshopdesktop.api.dto.common.BulkDeleteRequest;
+import org.example.petshopdesktop.api.dto.common.PageResponse;
 import org.example.petshopdesktop.api.dto.product.ProductRequest;
 import org.example.petshopdesktop.api.dto.product.ProductResponse;
 
+import java.net.URLEncoder;
+import java.nio.charset.StandardCharsets;
 import java.util.List;
 
 public class ProductApi {
@@ -23,10 +26,17 @@ public class ProductApi {
     public List<ProductResponse> listProducts(String query) throws Exception {
         String path = "/api/v1/products?page=0&size=1000";
         if (query != null && !query.isEmpty()) {
-            path += "&q=" + query;
+            path += "&q=" + URLEncoder.encode(query, StandardCharsets.UTF_8);
         }
-        String response = apiClient.get(path, String.class);
+        String response = apiClient.getRawResponse(path);
-        return apiClient.getObjectMapper().readValue(response, new TypeReference<List<ProductResponse>>() {});
+        PageResponse<ProductResponse> pageResponse = apiClient.getObjectMapper().readValue(
+            response,
+            new TypeReference<PageResponse<ProductResponse>>() {}
+        );
+        if (pageResponse == null) {
+            throw new IllegalStateException("Null response from products endpoint");
+        }
+        return pageResponse.getContent();
     }
 
     public ProductResponse createProduct(ProductRequest request) throws Exception {

src/main/java/org/example/petshopdesktop/api/endpoints/ProductSupplierApi.java

@@ -3,9 +3,12 @@ package org.example.petshopdesktop.api.endpoints;
 import com.fasterxml.jackson.core.type.TypeReference;
 import org.example.petshopdesktop.api.ApiClient;
 import org.example.petshopdesktop.api.dto.common.BulkDeleteRequest;
+import org.example.petshopdesktop.api.dto.common.PageResponse;
 import org.example.petshopdesktop.api.dto.productsupplier.ProductSupplierRequest;
 import org.example.petshopdesktop.api.dto.productsupplier.ProductSupplierResponse;
 
+import java.net.URLEncoder;
+import java.nio.charset.StandardCharsets;
 import java.util.List;
 
 public class ProductSupplierApi {
@@ -23,10 +26,17 @@ public class ProductSupplierApi {
     public List<ProductSupplierResponse> listProductSuppliers(String query) throws Exception {
         String path = "/api/v1/product-suppliers?page=0&size=1000";
         if (query != null && !query.isEmpty()) {
-            path += "&q=" + query;
+            path += "&q=" + URLEncoder.encode(query, StandardCharsets.UTF_8);
         }
-        String response = apiClient.get(path, String.class);
+        String response = apiClient.getRawResponse(path);
-        return apiClient.getObjectMapper().readValue(response, new TypeReference<List<ProductSupplierResponse>>() {});
+        PageResponse<ProductSupplierResponse> pageResponse = apiClient.getObjectMapper().readValue(
+            response,
+            new TypeReference<PageResponse<ProductSupplierResponse>>() {}
+        );
+        if (pageResponse == null) {
+            throw new IllegalStateException("Null response from product-suppliers endpoint");
+        }
+        return pageResponse.getContent();
     }
 
     public ProductSupplierResponse createProductSupplier(ProductSupplierRequest request) throws Exception {

src/main/java/org/example/petshopdesktop/api/endpoints/PurchaseOrderApi.java

@@ -2,8 +2,11 @@ package org.example.petshopdesktop.api.endpoints;
 
 import com.fasterxml.jackson.core.type.TypeReference;
 import org.example.petshopdesktop.api.ApiClient;
+import org.example.petshopdesktop.api.dto.common.PageResponse;
 import org.example.petshopdesktop.api.dto.purchaseorder.PurchaseOrderResponse;
 
+import java.net.URLEncoder;
+import java.nio.charset.StandardCharsets;
 import java.util.List;
 
 public class PurchaseOrderApi {
@@ -21,9 +24,16 @@ public class PurchaseOrderApi {
     public List<PurchaseOrderResponse> listPurchaseOrders(String query) throws Exception {
         String path = "/api/v1/purchase-orders?page=0&size=1000";
         if (query != null && !query.isEmpty()) {
-            path += "&q=" + query;
+            path += "&q=" + URLEncoder.encode(query, StandardCharsets.UTF_8);
         }
-        String response = apiClient.get(path, String.class);
+        String response = apiClient.getRawResponse(path);
-        return apiClient.getObjectMapper().readValue(response, new TypeReference<List<PurchaseOrderResponse>>() {});
+        PageResponse<PurchaseOrderResponse> pageResponse = apiClient.getObjectMapper().readValue(
+            response,
+            new TypeReference<PageResponse<PurchaseOrderResponse>>() {}
+        );
+        if (pageResponse == null) {
+            throw new IllegalStateException("Null response from purchase-orders endpoint");
+        }
+        return pageResponse.getContent();
     }
 }

src/main/java/org/example/petshopdesktop/api/endpoints/SaleApi.java

@@ -2,9 +2,12 @@ package org.example.petshopdesktop.api.endpoints;
 
 import com.fasterxml.jackson.core.type.TypeReference;
 import org.example.petshopdesktop.api.ApiClient;
+import org.example.petshopdesktop.api.dto.common.PageResponse;
 import org.example.petshopdesktop.api.dto.sale.SaleRequest;
 import org.example.petshopdesktop.api.dto.sale.SaleResponse;
 
+import java.net.URLEncoder;
+import java.nio.charset.StandardCharsets;
 import java.util.List;
 
 public class SaleApi {
@@ -22,10 +25,17 @@ public class SaleApi {
     public List<SaleResponse> listSales(int page, int size, String query) throws Exception {
         String path = "/api/v1/sales?page=" + page + "&size=" + size;
         if (query != null && !query.isEmpty()) {
-            path += "&q=" + query;
+            path += "&q=" + URLEncoder.encode(query, StandardCharsets.UTF_8);
         }
-        String response = apiClient.get(path, String.class);
+        String response = apiClient.getRawResponse(path);
-        return apiClient.getObjectMapper().readValue(response, new TypeReference<List<SaleResponse>>() {});
+        PageResponse<SaleResponse> pageResponse = apiClient.getObjectMapper().readValue(
+            response,
+            new TypeReference<PageResponse<SaleResponse>>() {}
+        );
+        if (pageResponse == null) {
+            throw new IllegalStateException("Null response from sales endpoint");
+        }
+        return pageResponse.getContent();
     }
 
     public SaleResponse getSale(Long id) throws Exception {

src/main/java/org/example/petshopdesktop/api/endpoints/ServiceApi.java

@@ -3,9 +3,12 @@ package org.example.petshopdesktop.api.endpoints;
 import com.fasterxml.jackson.core.type.TypeReference;
 import org.example.petshopdesktop.api.ApiClient;
 import org.example.petshopdesktop.api.dto.common.BulkDeleteRequest;
+import org.example.petshopdesktop.api.dto.common.PageResponse;
 import org.example.petshopdesktop.api.dto.service.ServiceRequest;
 import org.example.petshopdesktop.api.dto.service.ServiceResponse;
 
+import java.net.URLEncoder;
+import java.nio.charset.StandardCharsets;
 import java.util.List;
 
 public class ServiceApi {
@@ -23,10 +26,17 @@ public class ServiceApi {
     public List<ServiceResponse> listServices(String query) throws Exception {
         String path = "/api/v1/services?page=0&size=1000";
         if (query != null && !query.isEmpty()) {
-            path += "&q=" + query;
+            path += "&q=" + URLEncoder.encode(query, StandardCharsets.UTF_8);
         }
-        String response = apiClient.get(path, String.class);
+        String response = apiClient.getRawResponse(path);
-        return apiClient.getObjectMapper().readValue(response, new TypeReference<List<ServiceResponse>>() {});
+        PageResponse<ServiceResponse> pageResponse = apiClient.getObjectMapper().readValue(
+            response,
+            new TypeReference<PageResponse<ServiceResponse>>() {}
+        );
+        if (pageResponse == null) {
+            throw new IllegalStateException("Null response from services endpoint");
+        }
+        return pageResponse.getContent();
     }
 
     public ServiceResponse createService(ServiceRequest request) throws Exception {

src/main/java/org/example/petshopdesktop/api/endpoints/SupplierApi.java

@@ -3,9 +3,12 @@ package org.example.petshopdesktop.api.endpoints;
 import com.fasterxml.jackson.core.type.TypeReference;
 import org.example.petshopdesktop.api.ApiClient;
 import org.example.petshopdesktop.api.dto.common.BulkDeleteRequest;
+import org.example.petshopdesktop.api.dto.common.PageResponse;
 import org.example.petshopdesktop.api.dto.supplier.SupplierRequest;
 import org.example.petshopdesktop.api.dto.supplier.SupplierResponse;
 
+import java.net.URLEncoder;
+import java.nio.charset.StandardCharsets;
 import java.util.List;
 
 public class SupplierApi {
@@ -23,10 +26,17 @@ public class SupplierApi {
     public List<SupplierResponse> listSuppliers(String query) throws Exception {
         String path = "/api/v1/suppliers?page=0&size=1000";
         if (query != null && !query.isEmpty()) {
-            path += "&q=" + query;
+            path += "&q=" + URLEncoder.encode(query, StandardCharsets.UTF_8);
         }
-        String response = apiClient.get(path, String.class);
+        String response = apiClient.getRawResponse(path);
-        return apiClient.getObjectMapper().readValue(response, new TypeReference<List<SupplierResponse>>() {});
+        PageResponse<SupplierResponse> pageResponse = apiClient.getObjectMapper().readValue(
+            response,
+            new TypeReference<PageResponse<SupplierResponse>>() {}
+        );
+        if (pageResponse == null) {
+            throw new IllegalStateException("Null response from suppliers endpoint");
+        }
+        return pageResponse.getContent();
     }
 
     public SupplierResponse createSupplier(SupplierRequest request) throws Exception {

src/main/java/org/example/petshopdesktop/api/endpoints/UserApi.java

@@ -2,9 +2,12 @@ package org.example.petshopdesktop.api.endpoints;
 
 import com.fasterxml.jackson.core.type.TypeReference;
 import org.example.petshopdesktop.api.ApiClient;
+import org.example.petshopdesktop.api.dto.common.PageResponse;
 import org.example.petshopdesktop.api.dto.user.UserRequest;
 import org.example.petshopdesktop.api.dto.user.UserResponse;
 
+import java.net.URLEncoder;
+import java.nio.charset.StandardCharsets;
 import java.util.List;
 
 public class UserApi {
@@ -22,10 +25,17 @@ public class UserApi {
     public List<UserResponse> listUsers(String query) throws Exception {
         String path = "/api/v1/users?page=0&size=1000";
         if (query != null && !query.isEmpty()) {
-            path += "&q=" + query;
+            path += "&q=" + URLEncoder.encode(query, StandardCharsets.UTF_8);
         }
-        String response = apiClient.get(path, String.class);
+        String response = apiClient.getRawResponse(path);
-        return apiClient.getObjectMapper().readValue(response, new TypeReference<List<UserResponse>>() {});
+        PageResponse<UserResponse> pageResponse = apiClient.getObjectMapper().readValue(
+            response,
+            new TypeReference<PageResponse<UserResponse>>() {}
+        );
+        if (pageResponse == null) {
+            throw new IllegalStateException("Null response from users endpoint");
+        }
+        return pageResponse.getContent();
     }
 
     public UserResponse createUser(UserRequest request) throws Exception {

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

@@ -54,17 +54,27 @@ public class LoginController {
             LoginRequest loginRequest = new LoginRequest(username, password);
             LoginResponse loginResponse = apiClient.post("/api/v1/auth/login", loginRequest, LoginResponse.class);
 
+            if (loginResponse == null) {
+                throw new IllegalStateException("Login response is null");
+            }
+
             String token = loginResponse.getToken();
             String roleStr = loginResponse.getRole();
+            if (token == null || roleStr == null) {
+                throw new IllegalStateException("Token or role is null");
+            }
             Role role = Role.valueOf(roleStr.toUpperCase());
 
             UserSession.getInstance().login(null, username, role, token);
 
             UserInfoResponse userInfo = apiClient.get("/api/v1/auth/me", UserInfoResponse.class);
+            if (userInfo == null) {
+                throw new IllegalStateException("User info is null");
+            }
             UserSession.getInstance().login(userInfo.getId(), username, role, token);
 
             List<DropdownOption> stores = DropdownApi.getInstance().getStores();
-            if (!stores.isEmpty()) {
+            if (stores != null && !stores.isEmpty()) {
                 UserSession.getInstance().setStoreId(stores.get(0).getId());
             }
 

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

@@ -67,8 +67,10 @@ public class AdoptionDialogController {
             try {
                 List<DropdownOption> pets = DropdownApi.getInstance().getPets();
                 Platform.runLater(() -> {
+                    if (pets != null) {
                         ObservableList<DropdownOption> petsObs = FXCollections.observableArrayList(pets);
                         cbPet.setItems(petsObs);
+                    }
                 });
             } catch (Exception e) {
                 Platform.runLater(() -> {
@@ -85,8 +87,10 @@ public class AdoptionDialogController {
             try {
                 List<DropdownOption> customers = DropdownApi.getInstance().getCustomers();
                 Platform.runLater(() -> {
+                    if (customers != null) {
                         ObservableList<DropdownOption> customersObs = FXCollections.observableArrayList(customers);
                         cbCustomer.setItems(customersObs);
+                    }
                 });
             } catch (Exception e) {
                 Platform.runLater(() -> {
@@ -144,7 +148,11 @@ public class AdoptionDialogController {
                 if (mode.equals("Add")) {
                     AdoptionApi.getInstance().createAdoption(request);
                 } else {
-                    Long adoptionId = Long.parseLong(lblAdoptionId.getText().split(": ")[1]);
+                    String[] parts = lblAdoptionId.getText().split(": ");
+                    if (parts.length < 2) {
+                        throw new IllegalStateException("Invalid adoption ID format");
+                    }
+                    Long adoptionId = Long.parseLong(parts[1]);
                     AdoptionApi.getInstance().updateAdoption(adoptionId, request);
                 }
 
@@ -197,7 +205,14 @@ public class AdoptionDialogController {
             }
 
             if (adoption.getAdoptionDate() != null && !adoption.getAdoptionDate().isEmpty()) {
+                try {
                     dpAdoptionDate.setValue(LocalDate.parse(adoption.getAdoptionDate()));
+                } catch (Exception e) {
+                    ActivityLogger.getInstance().logException(
+                        "AdoptionDialogController.displayAdoptionDetails",
+                        e,
+                        "Parsing adoption date");
+                }
             }
 
             for (String status : cbAdoptionStatus.getItems()) {

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

@@ -80,9 +80,15 @@ public class AppointmentDialogController {
                 List<DropdownOption> pets = DropdownApi.getInstance().getPets();
 
                 Platform.runLater(() -> {
+                    if (services != null) {
                         cbService.setItems(FXCollections.observableArrayList(services));
+                    }
+                    if (customers != null) {
                         cbCustomer.setItems(FXCollections.observableArrayList(customers));
+                    }
+                    if (pets != null) {
                         cbPet.setItems(FXCollections.observableArrayList(pets));
+                    }
                 });
             } catch (Exception e) {
                 Platform.runLater(() -> {
@@ -163,15 +169,29 @@ public class AppointmentDialogController {
         selectedAppointment = appt;
         lblAppointmentId.setText("ID: " + appt.getAppointmentId());
 
+        try {
             dpAppointmentDate.setValue(
                     java.time.LocalDate.parse(appt.getAppointmentDate())
             );
+        } catch (Exception e) {
+            ActivityLogger.getInstance().logException(
+                "AppointmentDialogController.displayAppointmentDetails",
+                e,
+                "Parsing appointment date");
+        }
 
         cbAppointmentStatus.setValue(appt.getAppointmentStatus());
 
+        try {
             LocalTime time = LocalTime.parse(appt.getAppointmentTime());
             cbHour.setValue(time.getHour());
             cbMinute.setValue(time.getMinute());
+        } catch (Exception e) {
+            ActivityLogger.getInstance().logException(
+                "AppointmentDialogController.displayAppointmentDetails",
+                e,
+                "Parsing appointment time");
+        }
 
         cbService.getItems().forEach(s -> {
             if (s.getId() == appt.getServiceId()) cbService.setValue(s);

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

@@ -70,6 +70,7 @@ public class InventoryDialogController {
         //Load product list from API into combobox
         try {
             List<ProductResponse> productResponses = ProductApi.getInstance().listProducts(null);
+            if (productResponses != null) {
                 ObservableList<Product> products = FXCollections.observableArrayList();
                 for (ProductResponse pr : productResponses) {
                     products.add(new Product(
@@ -81,6 +82,7 @@ public class InventoryDialogController {
                     ));
                 }
                 cbProduct.setItems(products);
+            }
         } catch (Exception e) {
             ActivityLogger.getInstance().logException(
                 "InventoryDialogController.initialize",
@@ -126,12 +128,22 @@ public class InventoryDialogController {
                 InventoryRequest request = new InventoryRequest();
                 Product selectedProduct = cbProduct.getSelectionModel().getSelectedItem();
                 request.setProductId((long) selectedProduct.getProdId());
-                request.setStockQuantity(Integer.parseInt(txtQuantity.getText()));
+                int quantity;
+                try {
+                    quantity = Integer.parseInt(txtQuantity.getText());
+                } catch (NumberFormatException e) {
+                    throw new IllegalArgumentException("Invalid quantity format");
+                }
+                request.setStockQuantity(quantity);
 
                 if (mode.equals("Add")) {
                     InventoryApi.getInstance().createInventory(request);
                 } else {
-                    Long inventoryId = Long.parseLong(lblInventoryId.getText().split(": ")[1]);
+                    String[] parts = lblInventoryId.getText().split(": ");
+                    if (parts.length < 2) {
+                        throw new IllegalStateException("Invalid inventory ID format");
+                    }
+                    Long inventoryId = Long.parseLong(parts[1]);
                     InventoryApi.getInstance().updateInventory(inventoryId, request);
                 }
 

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

@@ -107,7 +107,11 @@ public class PetDialogController {
                 if(mode.equals("Add")) {
                     PetApi.getInstance().createPet(request);
                 } else {
-                    Long petId = Long.parseLong(lblPetId.getText().split(": ")[1]);
+                    String[] parts = lblPetId.getText().split(": ");
+                    if (parts.length < 2) {
+                        throw new IllegalStateException("Invalid pet ID format");
+                    }
+                    Long petId = Long.parseLong(parts[1]);
                     PetApi.getInstance().updatePet(petId, request);
                 }
 
@@ -142,9 +146,18 @@ public class PetDialogController {
         request.setSpecies(txtPetSpecies.getText());
         request.setBreed(txtPetBreed.getText());
         request.setPetStatus(cbPetStatus.getValue());
+        try {
             request.setPrice(new BigDecimal(txtPetPrice.getText()));
+        } catch (NumberFormatException e) {
+            throw new IllegalArgumentException("Invalid price format");
+        }
 
-        int age = Integer.parseInt(txtPetAge.getText());
+        int age;
+        try {
+            age = Integer.parseInt(txtPetAge.getText());
+        } catch (NumberFormatException e) {
+            throw new IllegalArgumentException("Invalid age format");
+        }
         LocalDate dateOfBirth = LocalDate.now().minusYears(age);
         request.setDateOfBirth(dateOfBirth);
 

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

@@ -70,14 +70,16 @@ public class ProductDialogController {
         //Set up combobox for selecting category
         try {
             List<DropdownOption> categories = DropdownApi.getInstance().getCategories();
+            if (categories != null) {
                 ObservableList<DropdownOption> categoriesObs = FXCollections.observableArrayList(categories);
                 cbProdCategory.setItems(categoriesObs);
+            }
         } catch (Exception e) {
             ActivityLogger.getInstance().logException(
                 "ProductDialogController.initialize",
                 e,
                 "Loading categories for combo box");
-            throw new RuntimeException(e);
+            System.out.println("Error loading categories: " + e.getMessage());
         }
 
     }
@@ -110,14 +112,24 @@ public class ProductDialogController {
             try {
                 ProductRequest request = new ProductRequest();
                 request.setProductName(txtProdName.getText());
-                request.setPrice(new BigDecimal(txtProdPrice.getText()));
+                BigDecimal price;
+                try {
+                    price = new BigDecimal(txtProdPrice.getText());
+                } catch (NumberFormatException e) {
+                    throw new IllegalArgumentException("Invalid price format");
+                }
+                request.setPrice(price);
                 request.setCategoryId(cbProdCategory.getSelectionModel().getSelectedItem().getId());
                 request.setDescription(txtProdDesc.getText());
 
                 if (mode.equals("Add")) {
                     ProductApi.getInstance().createProduct(request);
                 } else {
-                    Long productId = Long.parseLong(lblProdId.getText().split(": ")[1]);
+                    String[] parts = lblProdId.getText().split(": ");
+                    if (parts.length < 2) {
+                        throw new IllegalStateException("Invalid product ID format");
+                    }
+                    Long productId = Long.parseLong(parts[1]);
                     ProductApi.getInstance().updateProduct(productId, request);
                 }
 

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

@@ -119,8 +119,12 @@ public class ProductSupplierDialogController {
                 var products = DropdownApi.getInstance().getProducts();
 
                 Platform.runLater(() -> {
+                    if (suppliers != null) {
                         cbSupplier.setItems(FXCollections.observableArrayList(suppliers));
+                    }
+                    if (products != null) {
                         cbProduct.setItems(FXCollections.observableArrayList(products));
+                    }
                 });
             } catch (Exception e) {
                 Platform.runLater(() -> {
@@ -204,7 +208,11 @@ public class ProductSupplierDialogController {
         ProductSupplierRequest request = new ProductSupplierRequest();
         request.setSupplierId(cbSupplier.getSelectionModel().getSelectedItem().getId());
         request.setProductId(cbProduct.getSelectionModel().getSelectedItem().getId());
+        try {
             request.setSupplierPrice(new BigDecimal(txtCost.getText()));
+        } catch (NumberFormatException e) {
+            throw new IllegalArgumentException("Invalid cost format");
+        }
         return request;
     }
 

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

@@ -99,7 +99,11 @@ public class SupplierDialogController {
                 if (mode.equals("Add")) {
                     SupplierApi.getInstance().createSupplier(request);
                 } else {
-                    Long supplierId = Long.parseLong(lblSupId.getText().split(": ")[1]);
+                    String[] parts = lblSupId.getText().split(": ");
+                    if (parts.length < 2) {
+                        throw new IllegalStateException("Invalid supplier ID format");
+                    }
+                    Long supplierId = Long.parseLong(parts[1]);
                     SupplierApi.getInstance().updateSupplier(supplierId, request);
                 }