ResponseEntityExceptionHandler — Base Class for Spring MVC Exception Handling

Direct Answer

ResponseEntityExceptionHandler is a base class for a @ControllerAdvice that centralizes handling of Spring MVC exceptions and returns ResponseEntity results. It supplies handlers and status mappings for many framework exceptions, but it does not automatically create your application's desired error-body format. Some conditions, including an unmapped URL, depend on MVC and Boot configuration and are not universally delivered as NoHandlerFoundException.

Code Example

@RestControllerAdvice
public class GlobalExceptionHandler extends ResponseEntityExceptionHandler {

    // Override to customize validation error response
    @Override
    protected ResponseEntity<Object> handleMethodArgumentNotValid(
            MethodArgumentNotValidException ex,
            HttpHeaders headers,
            HttpStatusCode status,
            WebRequest request) {
        
        var errors = ex.getBindingResult().getFieldErrors().stream()
                .map(err -> err.getField() + ": " + err.getDefaultMessage())
                .toList();
        
        var errorResponse = new ValidationErrorResponse(
                "Validation failed",
                errors,
                LocalDateTime.now()
        );
        
        return ResponseEntity.status(HttpStatus.BAD_REQUEST).body(errorResponse);
    }
}

record ValidationErrorResponse(String message, List<String> errors, LocalDateTime timestamp) {}

Common Mistakes & Pitfalls

• Handling Spring exceptions twice: Freshers often write an @ExceptionHandler(MethodArgumentNotValidException.class) method in their advice class that already extends ResponseEntityExceptionHandler — this creates a conflict because the base class already handles it. The correct approach is to override the protected handleMethodArgumentNotValid() method instead.
• Not calling super when needed: When overriding a handle method, freshers sometimes write completely custom logic and forget that calling super.handleXxx() can provide a good starting point. If you just want to add logging, call super and wrap the result.
• Wrong exception names: Confusing MethodArgumentNotValidException (validation failures on @Valid DTOs) with ConstraintViolationException (validation failures on method parameters with @Validated on the class). ResponseEntityExceptionHandler only handles the first one by default.