1. Introduction
In this quick article, we provide a concise overview of the Spring @RequestBody and @ResponseBody annotations.
2. @RequestBody
Simply put, the @RequestBody annotation maps the HttpRequest body to a transfer or domain object, enabling automatic deserialization of the inbound HttpRequest body onto a Java object.
First, let’s have a look at a Spring controller method:
@PostMapping("/request") public ResponseEntity postController( @RequestBody LoginForm loginForm) { exampleService.fakeAuthenticate(loginForm); return ResponseEntity.ok(HttpStatus.OK); }
Spring automatically deserializes the JSON into a Java type assuming an appropriate one is specified. By default, the type we annotate with the @RequestBody annotation must correspond to the JSON sent from our client-side controller:
public class LoginForm { private String username; private String password; // ... }
Here, the object we use to represent the HttpRequest body maps to our LoginForm object.
Let’s test this using CURL:
curl -i \ -H "Accept: application/json" \ -H "Content-Type:application/json" \ -X POST --data '{"username": "johnny", "password": "password"}' "https://localhost:8080/.../request"
This is all that is needed for a Spring REST API and an Angular client using the @RequestBody annotation!
3. @ResponseBody
The @ResponseBody annotation tells a controller that the object returned is automatically serialized into JSON and passed back into the HttpResponse object.
Suppose we have a custom Response object:
public class ResponseTransfer { private String text; // standard getters/setters }
Next, the associated controller can be implemented:
@Controller @RequestMapping("/post") public class ExamplePostController { @Autowired ExampleService exampleService; @PostMapping("/response") @ResponseBody public ResponseTransfer postResponseController( @RequestBody LoginForm loginForm) { return new ResponseTransfer("Thanks For Posting!!!"); } }
In the developer console of our browser or using a tool like Postman, we can see the following response:
{"text":"Thanks For Posting!!!"}
Remember, we don’t need to annotate the @RestController-annotated controllers with the @ResponseBody annotation since it’s done by default here.
4. Conclusion
We’ve built a simple Angular client for the Spring app that demonstrates how to use the @RestController and @ResponseBody annotations.
As always code samples are available over on GitHub.