This post is a follow up on the excellent article by Bruno Leite Guide to Spring Boot REST API Error Handling, about the error handling implementation strategy in Spring MVC.

Here we’ll apply some minor improvements over Bruno’s implementation of the class RestExceptionHandler.

The class is the focal point of the package, as its singleton instance will be called by Spring whenever a registered exception is raised during the flow of a web request. Exceptions are handled in 2 slightly different modes:

  • Overriding a method: The class extends ResponseEntityExceptionHandler, which is an abstract base for @ControllerAdvice annotated classes; a number of exceptions are already handled by the parent class, therefore it’s needed to override an existing method in order to change this default behavior;
  • Decorating a method with @ExceptionHandler annotation: Exceptions not managed in the parent class are handled by adding new methods decorated with the mentioned annotation;

Simplification of @ExceptionHandler annotated methods

The first improvement is the substitution of the class annotation @ControllerAdvice with the more specific @RestControllerAdvice, which is simply a composition of @ControllerAdvice and @ResponseBody class annotations. The result is that @ResponseBody is applied by default to all class’s methods, and this permits a little simplification of the methods annotated with @ExceptionHandler. These methods now return directly the ApiError object instead of using ResponseEntity<Object> and define the HTTP response status with the use of @ResponseStatus annotation.

Removal of the HTTP status from ApiError

The second improvement is the removal of the HTTP status from the ApiError class. This improves the decoupling between the class and the HTTP stack, making it more suitable for reuse in cases where the communication is not based on HTTP.

Find below a small excerpt of the changes applied:

public class RestExceptionHandler extends ResponseEntityExceptionHandler {
protected ApiError handleEntityNotFound(
        EntityNotFoundException ex) {
    ApiError apiError = new ApiError();
    return apiError;

The code is available in the forked github repository.