Earlier in Spring/Spring Boot, to Map a GET or POST or DELETE or any HTTP method request handler, we would write something like below:

@RestController
@RequestMapping("/api/books")
public class BookAPIController {
  @RequestMapping
  public ResponseEntity<?> getBooks(){

  }

  @RequestMapping("/{book_id}")
  public ResponseEntity<?> getBook(@PathVariable("book_id") String bookId){

  }

  @RequestMapping(method = RequestMethod.POST)
  public ResponseEntity<?> addNewBook(@RequestBody Map<String, Object> requestBody){

  }

  @RequestMapping(method = RequestMethod.POST, value="/{book_id}")
  public ResponseEntity<?> editBook(@PathVariable("book_id") String bookId){

  }

  @RequestMapping(method = RequestMethod.DELETE, value="/{book_id}")
  public ResponseEntity<?> deleteBook(@PathVariable("book_id") String bookId){

  }
}

But with Spring Framework 4.3 and Spring Boot 1.4 (which now uses Spring Framework 4.3), we have some new annotations to map the HTTP methods to request handlers for the following HTTP methods: GET, POST, PUT, PATCH, DELETE. These new annotations are namely: @GetMapping, @PostMapping, @PutMapping, @PatchMapping, @DeleteMapping. So the above code now looks like:

@RestController
@RequestMapping("/api/books")
public class BookAPIController {
  @GetMapping
  public ResponseEntity<?> getBooks(){}

  @GetMapping("/{book_id}")
  public ResponseEntity<?> getBook(
    @PathVariable("book_id") String bookId
  ){}

  @PostMapping
  public ResponseEntity<?> addNewBook(
    @RequestBody Map<String, Object> requestBody
  ){}

  @PostMapping("/{book_id}")
  public ResponseEntity<?> editBook(
    @PathVariable("book_id") String bookId
  ){}

  @DeleteMapping("/{book_id}")
  public ResponseEntity<?> deleteBook(
   @PathVariable("book_id") String bookId
  ){}
}

These new annotations aid in improving the code readability and also reducing the annotation text to some extent.