Exception Handling with Spring Boot Application

Exception and error handling is one of the most crucial when it comes to web service. It is also the most important as the correct respond should be given to the service consumer. This is not an easy task. You may have to code a wrapper class for error handling. But with spring boot this has become very easy.

This blog post is about how a thrown exception can be handled as the response.

METHOD 1:

package com.example.project.exceptions;

import org.springframework.http.HttpStatus;
import org.springframework.web.bind.annotation.ResponseStatus;

@ResponseStatus(value= HttpStatus.NOT_FOUND, reason="No such Movie")
public class MovieNotFoundException extends Exception {
}

The exception class must be annotated with @ResponseStatus. This defines the response to be returned when the exception is thrown.

So if the controller is as follows,

package com.example.project.controllers;

import com.example.package.models.Movie;
import com.example.package.services.MovieService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.*;

import java.util.List;

@RestController
public class MovieController {

    @Autowired
    private MovieService movieService;

    @ResponseBody
    @RequestMapping(value = "/movies/{id}", method = RequestMethod.GET)
    public Movie getMovieByName(@PathVariable String id) {
        if(movieService.getMovieById(id)!=null)
             return movieService.getMovieById(id);
        throw new MovieNotFoundException();
    }
}

Instead of throwing the Exception or HTTP code 500 directly to the user, we can manipulate it to give the necessary response.

METHOD 2:

You can also use an ExceptionHandler Controller class to handle all the exceptions. 

You can use this when the exceptions is predefined. 

@RestController
public class MovieController {

    @Autowired
    private MovieService movieService;

    @ResponseBody
    @RequestMapping(value = "/movies/{id}", method = RequestMethod.GET)
    public Movie getMovieByName(@PathVariable String id) {
        if(movieService.getMovieById(id)!=null)
             return movieService.getMovieById(id);
        throw new MovieNotFoundException();
    }

    @ExceptionHandler({ ParseException.class })
        public void handleException() {
    }
}

The issue with using this method is that this handling is available for only this particular controller and it is not available globally. So you will have to repeat this in other controllers as well.

However similar to these, spring boot provides many other exception handling techniques which are very handy.