Exploring basic features of exception handling in Spring (@ControllerAdvice).

Reference: https://docs.spring.io/spring-framework/docs/current/javadoc-api/org/springframework/web/bind/annotation/ControllerAdvice.html
Reference: https://spring.io/blog/2013/11/01/exception-handling-in-spring-mvc
Reference: http://www.baeldung.com/exception-handling-for-rest-with-spring

Before Spring 3.2, the main approach to handling exceptions in a Spring MVC application was @ExceptionHandler annotation.

After 3.2 we now have the new @ControllerAdvice annotation to address the limitations of the previous one.

• @ExceptionHandler

  public class FooController{
       
      //...
      @ExceptionHandler({ CustomException1.class, CustomException2.class })
      public void handleException() {
          //
      }
  }
  

  drawback: is active only for that particular Controller.

A controller advice allows you to use similar exception handling techniques to @ExceptionHandler but apply them across the whole application, not just to an individual controller. You can think of them as an annotation driven interceptor.

Any class annotated with @ControllerAdvice becomes a controller-advice, then we have to write method that will handle specific exception:

@ResponseStatus(code = HttpStatus.NOT_FOUND)
@ExceptionHandler(EntityNotFoundException.class)
@ResponseBody
ApplicationExceptionAsJSON entityNotFoundException(@NonNull HttpServletRequest request, 
                                                          @NonNull EntityNotFoundException ex) {
    Preconditions.checkArgument(nonNull(request.getRequestURI()));
    Preconditions.checkArgument(nonNull(ex.getLocalizedMessage()));
    
    return ApplicationExceptionAsJSON.builder()
            .url(request.getRequestURI())
            .message(ex.getLocalizedMessage())
            .build();
}

• EntityNotFoundExceptionInterceptor is @ControllerAdvice