Difference between @ControllerAdvice and @RestcontrollerAdvice in SpringBoot

Both @ControllerAdvice and @RestControllerAdvice are annotations in Spring that provide centralized exception handling, model binding, and other cross-cutting concerns across multiple controllers. However, there is a key difference in how they handle the response format, particularly in RESTful web services.

1. @ControllerAdvice:

• Purpose: It is used for handling exceptions and applying cross-cutting logic across all controllers (whether REST or non-REST).
• Response Type: It typically works with controllers that use @Controller, where the view layer (like HTML, JSP, or Thymeleaf) is returned. By default, the methods in @ControllerAdvice return view names and can use ModelAndView for rendering views.
• When to Use: Use it when you have both REST and non-REST (traditional MVC) controllers in your application and you want to handle exceptions, model binding, or other concerns for both.

Example:

import org.springframework.ui.Model;
import org.springframework.web.bind.annotation.ControllerAdvice;
import org.springframework.web.bind.annotation.ExceptionHandler;
import org.springframework.web.servlet.ModelAndView;

@ControllerAdvice
public class GlobalControllerAdvice {

    @ExceptionHandler(Exception.class)
    public ModelAndView handleException(Exception ex, Model model) {
        ModelAndView mav = new ModelAndView();
        mav.addObject("message", ex.getMessage());
        mav.setViewName("error");
        return mav;  // Will render "error" view (HTML page)
    }
}

In this case, @ControllerAdvice is designed to handle both REST and non-REST responses, and here it’s returning a view (error.jsp, for instance).

2. @RestControllerAdvice:

• Purpose: It is specifically designed for RESTful services (APIs) and provides a way to handle exceptions and apply other cross-cutting logic for controllers annotated with @RestController.
• Response Type: Since it is intended for REST controllers, it always returns the response as JSON (or other suitable HTTP response types like XML if configured). It combines @ControllerAdvice and @ResponseBody, meaning that the response from the exception handler is directly written to the HTTP response body, usually in JSON format.
• When to Use: Use it when you’re developing a REST API and want to centralize exception handling or cross-cutting logic for controllers that return JSON or other HTTP response data formats.

Example:

import org.springframework.http.HttpStatus;
import org.springframework.http.ResponseEntity;
import org.springframework.web.bind.annotation.ExceptionHandler;
import org.springframework.web.bind.annotation.RestControllerAdvice;

@RestControllerAdvice
public class GlobalRestControllerAdvice {

    @ExceptionHandler(Exception.class)
    public ResponseEntity<String> handleException(Exception ex) {
        return new ResponseEntity<>(ex.getMessage(), HttpStatus.INTERNAL_SERVER_ERROR);
    }
}

In this case, @RestControllerAdvice ensures that the response is automatically serialized into JSON or another appropriate format and returned to the client. No view is rendered here.

Key Differences:

When to Use Which:

• Use @ControllerAdvice when you are building a traditional web application with a view layer (e.g., HTML, Thymeleaf, JSP) and want to handle exceptions or other concerns across multiple controllers.
• Use @RestControllerAdvice when building RESTful web services, and you want centralized exception handling for controllers that return JSON or XML responses.

By choosing the appropriate advice annotation based on your application’s needs, you can ensure that your exceptions are handled in a consistent and appropriate manner for the type of controllers you’re using.