@RequestMapping(value = "/todos/{id}", method = RequestMethod.PUT)
 public ResponseEntity<Todo> update(@PathVariable Long id, @RequestBody Todo todo) {
   validate(id, todo);
   return new ResponseEntity<>(todoService.save(todo), OK);
 }
 @RequestMapping(value = "/todos", method = RequestMethod.POST)
 public ResponseEntity<Todo> create(@RequestBody @Valid Todo todo) {
   return new ResponseEntity<>(todoService.save(todo), HttpStatus.CREATED);
 }