Spring 引导 ResponseEntity 不操作 HTTP 响应

Question

我在响应实体异常处理方面遇到问题。正如所见，我的响应实体错误并未更改 HTTP 响应。

我的代码

      public ResponseEntity<User> retriveUser(@PathVariable int id){
      Optional<User> foundUser;
      foundUser= userRepo.findById(id);
      
      if(foundUser.get()==null) {
          return new ResponseEntity<>(foundUser.get(),HttpStatus.HttpStatus.NOT_FOUND);
          }
      
      else {
          return new ResponseEntity<>(foundUser.get(),HttpStatus.OK);
          }    
  }

Answer 1

将您的代码更改为以下内容

if(foundUser.isPresent()) {
          return new ResponseEntity<>(foundUser.get(),HttpStatus.OK);
} else {
          return new ResponseEntity<>(foundUser.get(),HttpStatus.HTTP_VERSION_NOT_SUPPORTED);
}

Answer 2

您的代码中有一些错误，首先 foundUser.get()==null 部分没有进入 if 块，因为它抛出错误。您可以检查 java document 以找出引发错误的原因。

还需要HttpStatus.NOT_FOUND而不是HttpStatus.HttpStatus.NOT_FOUND.
在“Not Found”这一行，这样optionalUser.get()方法就不会报错；你也必须删除它。

@GetMapping("/user/{id}")
public ResponseEntity<User> retrieveUser(@PathVariable int id) {
   Optional<User> optionalUser = userRepo.findById(id);
   if (!optionalUser.isPresent()) {
      return new ResponseEntity<>(null, HttpStatus.NOT_FOUND);
   } else {
      return new ResponseEntity<>(optionalUser.get(), HttpStatus.OK);
   }
}

Answer 3

如果值不存在，您不应调用 get() 方法。你能像下面那样试试吗

public ResponseEntity<User> retriveUser(@PathVariable int id){
      Optional<User> foundUser = userRepo.findById(id);
      
      if(foundUser.isPresent()) {
          return new ResponseEntity<>(foundUser.get(),HttpStatus.HttpStatus.OK);
      }else {
          return new ResponseEntity<>(null,HttpStatus.NOT_FOUND);
          //or just return not found status code 
          //return new ResponseEntity<>(HttpStatus.NOT_FOUND); 
     }    
  }

Answer 4

虽然目前接受的答案已经包含了它需要的所有细节，但我已经在这里添加了我的建议，请看一看。你可以去掉 if else 块

    @RestController
    @RequestMapping(path = "users")
    static class UserController {

        private final Map<Long, UserInfo> users = new HashMap<>();

        UserController() {
            users.put(1L, new UserInfo(1L, "User 1"));
            users.put(2L, new UserInfo(1L, "User 2"));
        }

        @GetMapping(path = "{id}")
        public ResponseEntity<UserInfo> get(@PathVariable("id") Long id) {
            return findUserById(id)
                    .map(ResponseEntity::ok)
                    .orElse(new ResponseEntity<>(UserInfo.notFoundUser(), HttpStatus.NOT_FOUND));
        }

        Optional<UserInfo> findUserById(@NonNull Long id) {
            return Optional.ofNullable(users.get(id));
        }

        static class UserInfo {
            Long id;
            String name;

            public UserInfo() {
            }

            public UserInfo(Long id, String name) {
                this.id = id;
                this.name = name;
            }

            public Long getId() {
                return id;
            }

            public void setId(Long id) {
                this.id = id;
            }

            public String getName() {
                return name;
            }

            public void setName(String name) {
                this.name = name;
            }

            static UserInfo notFoundUser() {
                return new UserInfo(-1L, null);
            }
        }
    }

Spring 引导 ResponseEntity 不操作 HTTP 响应

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