@ResponseBody , ResponseEntity Spring return Object as JSON

Question

I'm using Spring version 4 ( spring data), I want to return Object as JSON , I wonderd that the following code worked even without annotating the user class wtih xmlRootElement:

@RequestMapping(value = "/resources/users", method = RequestMethod.GET)
public ResponseEntity<User> getUserByLogonId(OAuth2Authentication auth) {

    String userLogonId = ((org.springframework.security.core.userdetails.User) auth.getUserAuthentication()
            .getPrincipal()).getUsername();
    UsersServices usersServices = new UsersServicesImpl(usersOperations);
    User user = usersServices.findByLogonId(userLogonId);
    HttpStatus userStatus = HttpStatus.NOT_FOUND;
    if (user != null) {
        userStatus = HttpStatus.FOUND;
    }
    return new ResponseEntity<User>(user, userStatus);
}

can any body explain ? is ResponseBody/ResponseEntity do the work itself ? when I need to annotate the object class to be returned as JSON.

Answer 1

@RestController itself adds @ResponseBody annotation. You can see it in the Github Issue

You can also check the official spring tutorials. Here you can check the below lines and examples:

These controller methods return simple POJOs - Collection<Bookmark>, and Bookmark, etc., in all but the add case. When an HTTP request comes in that specifies an Accept header, Spring MVC loops through the configured HttpMessageConverter until it finds one that can convert from the POJO domain model types into the content-type specified in the Accept header, if so configured.

You can also follow the below lines and examples from Official doc

@RestController is a stereotype annotation that combines @ResponseBody and @Controller. More than that, it gives more meaning to your Controller and also may carry additional semantics in future releases of the framework.

And,

As with @RequestBody and @ResponseBody, Spring uses HttpMessageConverter to convert from and to the request and response streams.