Tukukkk

When building a rest api using spring boot what is the best way to handle exceptions from the service level and pass them to the controller, so the client gets a custom json error message.

{

    "message": "some error"

}

Endpoint from controller

@PostMapping("/login")

public String login(@RequestBody @Valid LoginDto loginDto) {

    return gson.toJson(userService.login(loginDto.getUsername(), loginDto.getPassword()));

} 

Service level code

public LoginResponseDto login(String username, String password) {



        try {

            //performs some checks

            ...

            return new LoginResponseDto(token.get());

        } catch (AuthenticationException e){

            LOGGER.info("Log in failed for user {}", username);

        }

    return new LoginResponseDto("login failed");

}

LoginResponseDto class

String token;

String message;



public LoginResponseDto(String message) {

    this.message = message;

}

Currently it is obviously returning the correctly message but not the correct status code, it will show status 200 with the error message in json.

You have some options:

1) Returning a message:

If you want to return a message something like this,

{

    "message": "some error"

}

What you can do is:

Option 1: Create a custom POJO class for error message and return the reference to the object of that POJO class.

Something like this:

ErrorMessage.java

package org.example;



public class ErrorMessage {

    private String message;



    public ErrorMessage(String message) {

        this.message = message;

    }



    public String getMessage() {

        return message;

    }



    public void setMessage(String message) {

        this.message = message;

    }

}

Request Handler Method in Controller:

@GetMapping("/login{?username, password}")

public ErrorMessage isUserAuthenticated(@RequestParam String username, @RequestParam String password) { 



    if (username.toLowerCase().contentEquals("root") && password.contentEquals("system")) {

        return new ErrorMessage("authenticated");

    }



    return null;

}

Option 2: Create a Map and insert key-value pairs that you want to have in the message.

Like this:

@GetMapping("/login{?username, password}")

public Map<String, String> isUserAuthenticated(@RequestParam String username, @RequestParam String password) { 

    Map<String, String> message = new HashMap<>();



    if (username.toLowerCase().contentEquals("root") && password.contentEquals("system")) {

        message.put("message", "authenticated");

    }



    return message;

}

2) Returning an error status code (highly recommended by me):

You may use ResponseEntity for this purpose.

@GetMapping("/login{?username, password}")

public ResponseEntity<?> isUserAuthenticated(@RequestParam String username, @RequestParam String password) { 

    if (username.toLowerCase().contentEquals("root") && password.contentEquals("system")) {

        return new ResponseEntity<>(HttpStatus.OK);

    }



    return new ResponseEntity<>(HttpStatus.NOT_FOUND);

}