spring-request-response-body
Spring’s RequestBody and ResponseBody Annotations
Further reading:
Guide to Spring Handler Mappings
The article explains how HandlerMapping implementation resolve URL to a particular Handler.
Quick Guide to Spring Controllers
A quick and practical guide to Spring Controllers – both for typical MVC apps and for REST APIs.
The Spring @Controller and @RestController Annotations
Learn about the differences between @Controller and @RestController annotations in Spring MVC.
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.
