Mastering @RequestBody and @ResponseBody in Spring MVC: A Quick Guide

1. Introduction

In this short article we briefly introduce the commonly used Spring MVC annotations @RequestBody and @ResponseBody.

2. @RequestBody

With @RequestBody Spring MVC automatically deserializes the HTTP request body into a Java object, typically mapping the JSON payload to a DTO.

Example controller method:

@PostMapping("/request")
public ResponseEntity postController(@RequestBody LoginForm loginForm) {
    exampleService.fakeAuthenticate(loginForm);
    return ResponseEntity.ok(HttpStatus.OK);
}

The LoginForm class:

public class LoginForm {
    private String username;
    private String password;
    // getters and setters
}

Testing with curl:

curl -i \
-H "Accept: application/json" \
-H "Content-Type:application/json" \
-X POST --data '{"username": "johnny", "password": "password"}' "https://localhost:8080/.../request"

3. @ResponseBody

@ResponseBody tells Spring to serialize the returned object to JSON and write it to the HTTP response body.

Example response class:

public class ResponseTransfer {
    private String text;
    // standard getters/setters
}

Controller using @ResponseBody:

@Controller
@RequestMapping("/post")
public class ExamplePostController {

    @Autowired
    ExampleService exampleService;

    @PostMapping("/response")
    @ResponseBody
    public ResponseTransfer postResponseController(@RequestBody LoginForm loginForm) {
        return new ResponseTransfer("Thanks For Posting!!!");
    }
}

Resulting JSON response:

{
    "text": "Thanks For Posting!!!"
}

Note: When a controller is annotated with @RestController, @ResponseBody is implicit.

4. Summary

We built a simple Spring application that receives JSON from an Angular client using @RequestBody and returns JSON using @ResponseBody or @RestController.