consolidate shared constants

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

@@ -7,6 +7,7 @@ import com.petshop.backend.entity.*;
 import com.petshop.backend.exception.BusinessException;
 import com.petshop.backend.exception.ResourceNotFoundException;
 import com.petshop.backend.repository.*;
+import com.petshop.backend.util.BusinessConstants;
 import com.stripe.Stripe;
 import com.stripe.exception.StripeException;
 import com.stripe.model.PaymentIntent;
@@ -24,7 +25,7 @@ import java.util.List;
 @Service
 public class CartService {
 
-    private static final int LOYALTY_POINTS_PER_DOLLAR = 20;
+    private static final int LOYALTY_POINTS_PER_DOLLAR = BusinessConstants.LOYALTY_POINTS_PER_DOLLAR;
 
     private final CartRepository cartRepository;
     private final CartItemRepository cartItemRepository;

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

@@ -1,6 +1,7 @@
 package com.petshop.backend.service;
 
 import com.petshop.backend.dto.common.BulkDeleteRequest;
+import com.petshop.backend.util.ImageValidationUtil;
 import com.petshop.backend.util.StringUtils;
 import com.petshop.backend.dto.pet.MyPetRequest;
 import com.petshop.backend.dto.pet.MyPetResponse;
@@ -31,7 +32,7 @@ import org.springframework.web.multipart.MultipartFile;
 
 import java.io.IOException;
 import java.util.List;
-import java.util.Locale;
+
 
 @Service
 public class PetService {
@@ -284,17 +285,7 @@ public class PetService {
         if (file == null || file.isEmpty()) {
             throw new BusinessException("Please select an image to upload");
         }
-        if (file.getSize() > 5 * 1024 * 1024) {
+        ImageValidationUtil.validate(file);
-            throw new BusinessException("Image file size must be less than 5MB");
-        }
-        String contentType = file.getContentType();
-        if (contentType == null) {
-            throw new BusinessException("Only JPG, PNG, and GIF images are allowed");
-        }
-        String normalized = contentType.toLowerCase(Locale.ROOT);
-        if (!normalized.equals("image/jpeg") && !normalized.equals("image/png") && !normalized.equals("image/gif")) {
-            throw new BusinessException("Only JPG, PNG, and GIF images are allowed");
-        }
     }
 
     private Pet findOwnedPet(Long ownerUserId, Long petId) {

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

@@ -1,6 +1,7 @@
 package com.petshop.backend.service;
 
 import com.petshop.backend.dto.common.BulkDeleteRequest;
+import com.petshop.backend.util.ImageValidationUtil;
 import com.petshop.backend.util.StringUtils;
 import com.petshop.backend.dto.product.ProductRequest;
 import com.petshop.backend.dto.product.ProductResponse;
@@ -21,7 +22,7 @@ import org.springframework.transaction.annotation.Transactional;
 import org.springframework.web.multipart.MultipartFile;
 
 import java.io.IOException;
-import java.util.Locale;
+
 
 @Service
 public class ProductService {
@@ -138,17 +139,7 @@ public class ProductService {
         if (file == null || file.isEmpty()) {
             throw new BusinessException("Please select an image to upload");
         }
-        if (file.getSize() > 5 * 1024 * 1024) {
+        ImageValidationUtil.validate(file);
-            throw new BusinessException("Image file size must be less than 5MB");
-        }
-        String contentType = file.getContentType();
-        if (contentType == null) {
-            throw new BusinessException("Only JPG, PNG, and GIF images are allowed");
-        }
-        String normalized = contentType.toLowerCase(Locale.ROOT);
-        if (!normalized.equals("image/jpeg") && !normalized.equals("image/png") && !normalized.equals("image/gif")) {
-            throw new BusinessException("Only JPG, PNG, and GIF images are allowed");
-        }
     }
 
     private void deleteStoredImageIfPresent(String storedImagePath) {

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

@@ -8,6 +8,7 @@ import com.petshop.backend.exception.ResourceNotFoundException;
 import com.petshop.backend.event.SaleReceiptEvent;
 import com.petshop.backend.repository.*;
 import com.petshop.backend.util.AuthenticationHelper;
+import com.petshop.backend.util.BusinessConstants;
 import com.petshop.backend.util.StringUtils;
 import org.springframework.context.ApplicationEventPublisher;
 import org.springframework.data.domain.Page;
@@ -24,8 +25,8 @@ import java.util.List;
 @Service
 public class SaleService {
 
-    private static final BigDecimal EMPLOYEE_DISCOUNT_PERCENT = new BigDecimal("0.10");
+    private static final BigDecimal EMPLOYEE_DISCOUNT_PERCENT = BusinessConstants.EMPLOYEE_DISCOUNT_PERCENT;
-    private static final int LOYALTY_POINTS_PER_DOLLAR = 20;
+    private static final int LOYALTY_POINTS_PER_DOLLAR = BusinessConstants.LOYALTY_POINTS_PER_DOLLAR;
 
     private final SaleRepository saleRepository;
     private final ProductRepository productRepository;

backend/src/main/java/com/petshop/backend/util/BusinessConstants.java

@@ -0,0 +1,11 @@
+package com.petshop.backend.util;
+
+import java.math.BigDecimal;
+
+public final class BusinessConstants {
+
+    private BusinessConstants() {}
+
+    public static final int LOYALTY_POINTS_PER_DOLLAR = 20;
+    public static final BigDecimal EMPLOYEE_DISCOUNT_PERCENT = new BigDecimal("0.10");
+}