我似乎不知道如何通过JSON添加具有外键的实体。
我有一个用户模型和一个帖子模型。一个用户可以在一个网站上发表不同的帖子。
这是一个多对一的关系。一个用户可以有多个帖子，而一个帖子只能有一个用户（发帖者）。帖子作为外键代表发帖用户的ID。
这是用户模型：

@Entity
@Data
@AllArgsConstructor
@NoArgsConstructor
@Builder
@Table(name = "user")
public class User {

//ID
@Id
@SequenceGenerator(
        name = "user_sequence",
        sequenceName = "user_sequence",
        allocationSize = 1
)
@GeneratedValue(
        strategy = GenerationType.IDENTITY,
        generator = "user_generator"
)
@Column(name = "id",nullable = false)
private int id;

private String username;
private String password;
private String email;

@JsonFormat(shape = JsonFormat.Shape.STRING, pattern="yyyy-MM-dd")
@Column(name = "creation_date")
private Date creationDate;

//RELATIONSHIP
@OneToMany(cascade = CascadeType.ALL, mappedBy = "user")
private List<Post> posts = new ArrayList<>();

/* =========== GETTERS AND SETTERS ===========*/

public int getId() {
    return id;
}

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

public String getUsername() {
    return username;
}

public void setUsername(String username) {
    this.username = username;
}

public String getPassword() {
    return password;
}

public void setPassword(String password) {
    this.password = password;
}

public String getEmail() {
    return email;
}

public void setEmail(String email) {
    this.email = email;
}

public Date getCreationDate() {
    return creationDate;
}

public void setCreationDate(Date creationDate) {
    this.creationDate = creationDate;
}

public List<Post> getPosts() {
    return posts;
}

public void setPosts(List<Post> posts) {
    this.posts = posts;
}
}

这是Post模型：

@Entity
    @Data
    @AllArgsConstructor
    @NoArgsConstructor
    @Builder
    @Table(name = "post")
    public class Post {

    //ID
    @Id
    @SequenceGenerator(
            name = "post_sequence",
            sequenceName = "post_sequence",
            allocationSize = 1
    )
    @GeneratedValue(
            strategy = GenerationType.IDENTITY,
            generator = "post_generator"
    )
    @Column(name = "id", nullable = false)
    private int id;

    @Column(name = "post_content")
    private String postContent;
    private String title;

    @JsonFormat(shape = JsonFormat.Shape.STRING, pattern="yyyy-MM-dd")
    @Column(name = "creation_date")
    private Date creationDate;

    //RELATIONSHIP
    @ManyToOne(cascade = CascadeType.ALL)
    @JoinColumn(name = "user_id", referencedColumnName = "id")
    private User user;

    /* ======== GETTERS AND SETTERS ======== */
    public int getId() {
        return id;
    }

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

    public String getPostContent() {
        return postContent;
    }

    public void setPostContent(String postContent) {
        this.postContent = postContent;
    }

    public String getTitle() {
        return title;
    }

    public void setTitle(String title) {
        this.title = title;
    }

    public Date getCreationDate() {
        return creationDate;
    }

    public void setCreationDate(Date creationDate) {
        this.creationDate = creationDate;
    }

    public User getUser() {
        return user;
    }

    public void setUser(User user) {
        this.user = user;
    }
    }

这是postController：

@RestController
public class PostController {

@Autowired
private PostService postService;

@PostMapping("/savePost")
public Post getPost(@Validated @RequestBody Post post) {
    return postService.savePost(post);
}

@GetMapping("getPost/{id}")
public Post getPost(@PathVariable int id) {
    return postService.getPost(id);
}

@PutMapping("/deletePost/{id}")
public void deletePost(int id) {
    postService.deletePost(id);
}

}

这是我在添加帖子时发送的JSON。Request to：地址：

{
"postContent": "some content",
"creationDate": "2022-07-31",
"title": "my title",
"user": 1
}

但是在postMan中我得到这个错误：

{
"timestamp": "2022-08-02T10:40:11.794+00:00",
"status": 400,
"error": "Bad Request",
"path": "/savePost"
}

在Spring我得到这个错误：JSON解析错误：无法构造x.model.User的示例（尽管至少存在一个创建者）：没有int/Int-argument构造函数/工厂方法要从Number值（1）反序列化;
如果我在JSON中发送请求，其中我调用用户“user_id”或“uderId”，那么我可以发送请求，但随后外键变为空

{
"creationDate": "2022-07-31",
"postContent": "some content",
"title": "my title",
"user_id": 1
}

发送的内容：

{
"id": 2,
"postContent": "some content",
"title": "my title",
"creationDate": "2022-07-31",
"user": null
}

有人知道我做错了什么吗？