@ControllerAdvice vs @RestControllerAdvice.

@ControllerAdvice:

• A global exception handler that works across multiple controllers.
• Typically returns a View (for MVC).

@RestControllerAdvice:

• Specialized version: @ControllerAdvice + @ResponseBody.
• Ideal for REST APIs. Returns serialized objects (like a custom ErrorResponse) directly to the client.

Method Example:

@ExceptionHandler(UserNotFoundException.class)
public ResponseEntity<ErrorDetails> handleUserNotFound(UserNotFoundException ex) {
    return new ResponseEntity<>(new ErrorDetails(ex.getMessage()), HttpStatus.NOT_FOUND);
}