@RequestMapping(value = "/book/{id}", method = RequestMethod.PUT) public ResponseEntity update(@RequestBody Book book) { for (Book b : this.books) { if (b.getId() == book.getId()) { b.setTitlu(book.getTitlu()); b.setEditura(book.getEditura()); return new ResponseEntity<Book>(b, new HttpHeaders(), HttpStatus.OK); } } return new ResponseEntity<String>(null, new HttpHeaders(), HttpStatus.NOT_FOUND); }