Question

我在Spring中有这个域类：

@Entity
@Table(name="Like")
public class Like {

@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
Long id;

@ManyToOne(cascade= CascadeType.MERGE, targetEntity = User.class)
@JoinColumn(name = "user_id")
@OnDelete(action= OnDeleteAction.CASCADE)
Set<User> user;

@OneToMany(mappedBy = "like", orphanRemoval = true ,cascade= CascadeType.ALL, targetEntity = Picture.class)
@OnDelete(action= OnDeleteAction.CASCADE)
Set<Picture> pictures;

public Like() {
}

public Like(Set<User> user) {
    this.user = user;
}

public Long getId() {
    return id;
}

public void setId(Long id) {
    this.id = id;
}
@JsonIgnore
public Set<User> getUser() {
    return user;
}
@JsonIgnore
public void setUser(Set<User> user) {
    this.user = user;
}

@JsonIgnore
public Set<Picture> getPictures() {
    return pictures;
}
@JsonIgnore
public void setPictures(Set<Picture> pictures) {
    this.pictures = pictures;
}
}
}

我在我的sql脚本中有这个表

CREATE TABLE IF NOT EXISTS `like` (
`id` INT NOT NULL PRIMARY KEY AUTO_INCREMENT,
`user_id` BIGINT,
FOREIGN KEY (user_id) REFERENCES `user`(id)
)ENGINE=InnoDB DEFAULT CHARSET=utf8;

当我在邮递员发送邮件请求时，这是一个问题：

java.lang.IllegalArgumentException：无法设置java.lang.Long字段 com.nyters.webapp.domain.User.id到java.util.HashSet

ControllerLike.java

  @RestController
  @RequestMapping("api/like")
  public class LikeController {

  private LikeService likeService;

  @Autowired
  public LikeController(LikeService likeService){
  this.likeService = likeService;
 }

   @RequestMapping(path = "/{id}", method = RequestMethod.GET)
    public ResponseEntity<LikeDTO> findOne(@PathVariable Long id) {
   LikeDTO pictureDTO = likeService.findOne(id);

   if (pictureDTO != null) {
    return new ResponseEntity<>(pictureDTO, HttpStatus.OK);
  } else {
    return new ResponseEntity<>(HttpStatus.NOT_FOUND);
  }
  }

@RequestMapping(method = RequestMethod.GET)
public ResponseEntity<List<LikeDTO>> findAll() {
List<LikeDTO> likeDTOs = likeService.findAll();

if (likeDTOs != null) {
    return new ResponseEntity<>(likeDTOs, HttpStatus.OK);
} else {
    return new ResponseEntity<>(HttpStatus.NOT_FOUND);
}
}

 @RequestMapping(method = RequestMethod.POST)
 public ResponseEntity<LikeDTO> save(@RequestBody String likeDtoString) 
 throws 
 IOException {
  LikeDTO likeDTO = new ObjectMapper().readValue(likeDtoString, 
  LikeDTO.class);
  LikeDTO saved = likeService.save(likeDTO);

if (saved != null) {
    return new ResponseEntity<>(saved, HttpStatus.OK);
} else {
    return new ResponseEntity<>(HttpStatus.NOT_FOUND);
}
}

Answer 1

首先@JsonIgnore使您的用户无法从json访问实体。第二步，您需要将已提交@ManyToOne的{{1}}更改为@OneToMany或@ManyToMany，或将类型更改为Set<User> user

<强>更新

嗯，User user意味着在当前班级中你只有一个元素（在我们的例子中是ManyToOne。它看起来如下：

User

在这种情况下，您的用户类如下所示：

class Like {
// init, class and bla-bla-bla

@ManyToOne(/*properties*/)
User user; // important - not Collection, Set or something else

所以，你可以想象（？）如下：@external_filed到current_field。我希望你理解

Answer 2

我猜概率是你的映射

<强> Like.java

@Fetch(value = FetchMode.SELECT)
@OneToMany(cascade = CascadeType.ALL)
@JoinColumn(name = "user_Id")
@JsonIgnore
private List<User> userList;
//based on user_Id u can fetch userList from DB

<强> User.java

@Id
@GeneratedValue(strategy = GenerationType.AUTO)
@Column(name = "user_Id")
private Long user_Id;

如何在Spring中发布用户列表

2 个答案: