Each controller class maps one or more requests to methods that process and execute the requests with provided inputs.

@RestController

@RestController is a class level annotation used to combine the functionality of the @Controller and @ResponseBody annotations.

• @Controller designates the annotated class as a controller
• @ResponseBody allows returned objects to be automatically serialized into JSON and returned in the HTTP response body

Deserializing to an Object

In Spring, applying the @RequestBody annotation to a controller’s method enables automatic deserialization of the HTTP request body to an object bound to the method’s argument.

@GetMapping("/book")
public Book isBookAvailable(@RequestBody Book book) {
  return library.find(book);
}