Rest API method get

Question

我应该如何检查从DB接收到实体并返回正确的响应？我使用restController。我想检查我是否从DB接收到用户。如果我找到了用户，我想返回用户和HttpStatus.OK，如果没有-HttpStatus.not_found.

public ResponseEntity<User> getUser(@PathVariable("id") int id) {
User User= this.userService.getUserById(id);
ResponseEntity<User> responseEntity = new ResponseEntity<>(HttpStatus.NOT_FOUND);
if (Objects.nonNull(user)) {
responseEntity = new ResponseEntity<>(user, HttpStatus.OK);
}
return responseEntity;
}

Answer 1

简单地说，如果您想使用Optional来检查数据库中用户的可用性：

public ResponseEntity<User> getUser(@PathVariable("id") int id) {
User User= this.userService.getUserById(id);
ResponseEntity<User> responseEntity = new ResponseEntity<>(HttpStatus.NOT_FOUND);
if (Optional.ofNullable(user).isPresent()) {
responseEntity = new ResponseEntity<>(user, HttpStatus.OK);
}
return responseEntity;
}

Answer 2

路径参数不能是可选的，您必须将2个URL映射到get控制器方法。试试下面的：

@RequestMapping(method=GET, value={"/", "/{id}"})
public ResponseEntity<User> getUser(@PathVariable Optional<Integer> id) {
if(!id.isPresent()){
return ResponseEntity.notFound().build();
}
User User= this.userService.getUserById(id);
ResponseEntity<User> responseEntity = new ResponseEntity<>(HttpStatus.NOT_FOUND);
if (Objects.nonNull(user)) {
responseEntity = new ResponseEntity<>(user, HttpStatus.OK);
}
return responseEntity;
}

此解决方案需要Spring 4.1+和Java 1.8。

Answer 3

对我来说，这是一种优雅的方式，通常id是Long类型的

public ResponseEntity<User> getUser(@PathVariable ("id") Long id) {
return Optional.of(this.userService.getUserById(id))
.map(u -> new ResponseEntity<>(u, HttpStatus.OK))
.orElse(new ResponseEntity<>(HttpStatus.NOT_FOUND));
}