fix (error handling): for validation errors with input fields

Author: Daggerpov

src/main/java/com/danielagapov/spawn/shared/exceptions/GlobalExceptionHandler.java

@@ -8,14 +8,18 @@
 import org.springframework.http.ResponseEntity;
 import org.springframework.security.authentication.BadCredentialsException;
 import org.springframework.security.core.userdetails.UsernameNotFoundException;
+import org.springframework.validation.FieldError;
+import org.springframework.web.bind.MethodArgumentNotValidException;
 import org.springframework.web.bind.annotation.ExceptionHandler;
 import org.springframework.web.bind.annotation.RestControllerAdvice;
 import org.springframework.web.context.request.WebRequest;
 
 import java.time.LocalDateTime;
 import java.util.HashMap;
+import java.util.List;
 import java.util.Map;
 import java.util.UUID;
+import java.util.stream.Collectors;
 
 @RestControllerAdvice
 public class GlobalExceptionHandler {
@@ -101,6 +105,31 @@ public ResponseEntity<Map<String, Object>> handleSecurityException(SecurityExcep
         return new ResponseEntity<>(response, HttpStatus.FORBIDDEN);
     }
 
+    /**
+     * Handle Bean Validation errors (e.g. @Valid on request bodies)
+     */
+    @ExceptionHandler(MethodArgumentNotValidException.class)
+    public ResponseEntity<Map<String, Object>> handleMethodArgumentNotValid(MethodArgumentNotValidException ex, WebRequest request) {
+        String errorId = UUID.randomUUID().toString();
+
+        List<String> fieldMessages = ex.getBindingResult().getFieldErrors().stream()
+                .map(FieldError::getDefaultMessage)
+                .collect(Collectors.toList());
+
+        String combinedMessage = String.join("; ", fieldMessages);
+
+        logger.warn("Validation error [" + errorId + "]: " + combinedMessage);
+
+        Map<String, Object> response = createErrorResponse(
+            "VALIDATION_ERROR",
+            combinedMessage,
+            HttpStatus.BAD_REQUEST,
+            errorId
+        );
+
+        return new ResponseEntity<>(response, HttpStatus.BAD_REQUEST);
+    }
+
     /**
      * Handle illegal argument exceptions (validation errors)
      */