backend/src/main/java/com/petshop/backend/service/CategoryService.java

@@ -21,11 +21,13 @@ public class CategoryService {
         this.categoryRepository = categoryRepository;
     }
 
+    @Transactional(readOnly = true)
     public Page<CategoryResponse> getAllCategories(String query, String type, Pageable pageable) {
         return categoryRepository.searchCategories(StringUtils.trimToNull(query), StringUtils.trimToNull(type), pageable)
                 .map(this::mapToResponse);
     }
 
+    @Transactional(readOnly = true)
     public CategoryResponse getCategoryById(Long id) {
         Category category = categoryRepository.findById(id)
                 .orElseThrow(() -> new ResourceNotFoundException("Category not found with id: " + id));

backend/src/main/java/com/petshop/backend/service/ServiceService.java

@@ -5,6 +5,7 @@ import com.petshop.backend.dto.service.ServiceRequest;
 import com.petshop.backend.dto.service.ServiceResponse;
 import com.petshop.backend.exception.ResourceNotFoundException;
 import com.petshop.backend.repository.ServiceRepository;
+import com.petshop.backend.util.StringUtils;
 import org.springframework.data.domain.Page;
 import org.springframework.data.domain.Pageable;
 import org.springframework.stereotype.Service;
@@ -21,9 +22,8 @@ public class ServiceService {
 
     @Transactional(readOnly = true)
     public Page<ServiceResponse> getAllServices(String query, String species, Pageable pageable) {
-        String q = (query != null && !query.trim().isEmpty()) ? query.trim() : null;
-        String sp = (species != null && !species.trim().isEmpty()) ? species.trim() : null;
-        return serviceRepository.searchServices(q, sp, pageable).map(this::mapToResponse);
+        return serviceRepository.searchServices(StringUtils.trimToNull(query), StringUtils.trimToNull(species), pageable)
+                .map(this::mapToResponse);
     }
 
     @Transactional(readOnly = true)
@@ -36,14 +36,7 @@ public class ServiceService {
     @Transactional
     public ServiceResponse createService(ServiceRequest request) {
         com.petshop.backend.entity.Service service = new com.petshop.backend.entity.Service();
-        service.setServiceName(request.getServiceName());
-        service.setServiceDesc(request.getServiceDesc());
-        service.setServicePrice(request.getServicePrice());
-        service.setServiceDuration(request.getServiceDuration());
-        if (request.getSpecies() != null) {
-            service.setSpecies(request.getSpecies());
-        }
-
+        applyFields(service, request);
         service = serviceRepository.save(service);
         return mapToResponse(service);
     }
@@ -52,15 +45,7 @@ public class ServiceService {
     public ServiceResponse updateService(Long id, ServiceRequest request) {
         com.petshop.backend.entity.Service service = serviceRepository.findById(id)
                 .orElseThrow(() -> new ResourceNotFoundException("Service not found with id: " + id));
-
-        service.setServiceName(request.getServiceName());
-        service.setServiceDesc(request.getServiceDesc());
-        service.setServicePrice(request.getServicePrice());
-        service.setServiceDuration(request.getServiceDuration());
-        if (request.getSpecies() != null) {
-            service.setSpecies(request.getSpecies());
-        }
-
+        applyFields(service, request);
         service = serviceRepository.save(service);
         return mapToResponse(service);
     }
@@ -78,6 +63,16 @@ public class ServiceService {
         serviceRepository.deleteAllById(request.getIds());
     }
 
+    private void applyFields(com.petshop.backend.entity.Service service, ServiceRequest request) {
+        service.setServiceName(request.getServiceName());
+        service.setServiceDesc(request.getServiceDesc());
+        service.setServicePrice(request.getServicePrice());
+        service.setServiceDuration(request.getServiceDuration());
+        if (request.getSpecies() != null) {
+            service.setSpecies(request.getSpecies());
+        }
+    }
+
     private ServiceResponse mapToResponse(com.petshop.backend.entity.Service service) {
         return new ServiceResponse(
             service.getServiceId(),

backend/src/main/java/com/petshop/backend/service/StoreService.java

@@ -6,6 +6,7 @@ import com.petshop.backend.dto.store.StoreResponse;
 import com.petshop.backend.entity.StoreLocation;
 import com.petshop.backend.exception.ResourceNotFoundException;
 import com.petshop.backend.repository.StoreRepository;
+import com.petshop.backend.util.StringUtils;
 import org.springframework.data.domain.Page;
 import org.springframework.data.domain.Pageable;
 import org.springframework.stereotype.Service;
@@ -20,16 +21,16 @@ public class StoreService {
         this.storeRepository = storeRepository;
     }
 
+    @Transactional(readOnly = true)
     public Page<StoreResponse> getAllStores(String query, Pageable pageable) {
-        Page<StoreLocation> stores;
-        if (query != null && !query.trim().isEmpty()) {
-            stores = storeRepository.searchStores(query, pageable);
-        } else {
-            stores = storeRepository.findAll(pageable);
-        }
+        String q = StringUtils.trimToNull(query);
+        Page<StoreLocation> stores = q != null
+                ? storeRepository.searchStores(q, pageable)
+                : storeRepository.findAll(pageable);
         return stores.map(this::mapToResponse);
     }
 
+    @Transactional(readOnly = true)
     public StoreResponse getStoreById(Long id) {
         StoreLocation store = storeRepository.findById(id)
                 .orElseThrow(() -> new ResourceNotFoundException("Store not found with id: " + id));
@@ -39,12 +40,7 @@ public class StoreService {
     @Transactional
     public StoreResponse createStore(StoreRequest request) {
         StoreLocation store = new StoreLocation();
-        store.setStoreName(request.getStoreName());
-        store.setAddress(request.getAddress());
-        store.setPhone(request.getPhone());
-        store.setEmail(request.getEmail());
-        store.setImageUrl(request.getImageUrl());
-
+        applyFields(store, request);
         store = storeRepository.save(store);
         return mapToResponse(store);
     }
@@ -53,13 +49,7 @@ public class StoreService {
     public StoreResponse updateStore(Long id, StoreRequest request) {
         StoreLocation store = storeRepository.findById(id)
                 .orElseThrow(() -> new ResourceNotFoundException("Store not found with id: " + id));
-
-        store.setStoreName(request.getStoreName());
-        store.setAddress(request.getAddress());
-        store.setPhone(request.getPhone());
-        store.setEmail(request.getEmail());
-        store.setImageUrl(request.getImageUrl());
-
+        applyFields(store, request);
         store = storeRepository.save(store);
         return mapToResponse(store);
     }
@@ -77,6 +67,14 @@ public class StoreService {
         storeRepository.deleteAllById(request.getIds());
     }
 
+    private void applyFields(StoreLocation store, StoreRequest request) {
+        store.setStoreName(request.getStoreName());
+        store.setAddress(request.getAddress());
+        store.setPhone(request.getPhone());
+        store.setEmail(request.getEmail());
+        store.setImageUrl(request.getImageUrl());
+    }
+
     private StoreResponse mapToResponse(StoreLocation store) {
         return new StoreResponse(
             store.getStoreId(),

backend/src/main/java/com/petshop/backend/service/SupplierService.java

@@ -6,6 +6,7 @@ import com.petshop.backend.dto.supplier.SupplierResponse;
 import com.petshop.backend.entity.Supplier;
 import com.petshop.backend.exception.ResourceNotFoundException;
 import com.petshop.backend.repository.SupplierRepository;
+import com.petshop.backend.util.StringUtils;
 import org.springframework.data.domain.Page;
 import org.springframework.data.domain.Pageable;
 import org.springframework.stereotype.Service;
@@ -20,16 +21,16 @@ public class SupplierService {
         this.supplierRepository = supplierRepository;
     }
 
+    @Transactional(readOnly = true)
     public Page<SupplierResponse> getAllSuppliers(String query, Pageable pageable) {
-        Page<Supplier> suppliers;
-        if (query != null && !query.trim().isEmpty()) {
-            suppliers = supplierRepository.searchSuppliers(query, pageable);
-        } else {
-            suppliers = supplierRepository.findAll(pageable);
-        }
+        String q = StringUtils.trimToNull(query);
+        Page<Supplier> suppliers = q != null
+                ? supplierRepository.searchSuppliers(q, pageable)
+                : supplierRepository.findAll(pageable);
         return suppliers.map(this::mapToResponse);
     }
 
+    @Transactional(readOnly = true)
     public SupplierResponse getSupplierById(Long id) {
         Supplier supplier = supplierRepository.findById(id)
                 .orElseThrow(() -> new ResourceNotFoundException("Supplier not found with id: " + id));
@@ -39,12 +40,7 @@ public class SupplierService {
     @Transactional
     public SupplierResponse createSupplier(SupplierRequest request) {
         Supplier supplier = new Supplier();
-        supplier.setSupCompany(request.getSupCompany());
-        supplier.setSupContactFirstName(request.getSupContactFirstName());
-        supplier.setSupContactLastName(request.getSupContactLastName());
-        supplier.setSupEmail(request.getSupEmail());
-        supplier.setSupPhone(request.getSupPhone());
-
+        applyFields(supplier, request);
         supplier = supplierRepository.save(supplier);
         return mapToResponse(supplier);
     }
@@ -53,13 +49,7 @@ public class SupplierService {
     public SupplierResponse updateSupplier(Long id, SupplierRequest request) {
         Supplier supplier = supplierRepository.findById(id)
                 .orElseThrow(() -> new ResourceNotFoundException("Supplier not found with id: " + id));
-
-        supplier.setSupCompany(request.getSupCompany());
-        supplier.setSupContactFirstName(request.getSupContactFirstName());
-        supplier.setSupContactLastName(request.getSupContactLastName());
-        supplier.setSupEmail(request.getSupEmail());
-        supplier.setSupPhone(request.getSupPhone());
-
+        applyFields(supplier, request);
         supplier = supplierRepository.save(supplier);
         return mapToResponse(supplier);
     }
@@ -77,6 +67,14 @@ public class SupplierService {
         supplierRepository.deleteAllById(request.getIds());
     }
 
+    private void applyFields(Supplier supplier, SupplierRequest request) {
+        supplier.setSupCompany(request.getSupCompany());
+        supplier.setSupContactFirstName(request.getSupContactFirstName());
+        supplier.setSupContactLastName(request.getSupContactLastName());
+        supplier.setSupEmail(request.getSupEmail());
+        supplier.setSupPhone(request.getSupPhone());
+    }
+
     private SupplierResponse mapToResponse(Supplier supplier) {
         return new SupplierResponse(
             supplier.getSupId(),