如何 POST 引用另一个 table 的新记录

Question

正在尝试使用 Spring 数据剩余：

我有 2 个实体，具有@ManyToOne 关系：

@Data
@Entity
@NoArgsConstructor
@Table(name = "tasks")
public class Task {

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

    @Column(nullable = false, length = 150)
    private String title;

    @Lob
    private String description;

}

@Data
@Entity
@NoArgsConstructor
@Table(name = "comments")
public class Comment {

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

    @ManyToOne(fetch = FetchType.LAZY, optional = false)
    @JoinColumn(name = "task_id", nullable = false)
    @OnDelete(action = OnDeleteAction.CASCADE)
    @JsonIgnore
    private Task task;

    @Lob
    @Column(nullable = false)
    private String comment;
}

我无法添加应该关联到 1 个任务的新评论

POST http://localhost:9000/api/comments
Content-Type: application/json

{
  "comment": "Some text",
  "task_id": 1
}

这个请求returns:

POST http://localhost:9000/api/comments

HTTP/1.1 409 
Vary: Origin
Vary: Access-Control-Request-Method
Vary: Access-Control-Request-Headers
Content-Type: application/json
Transfer-Encoding: chunked
Date: Wed, 01 Jul 2020 16:36:25 GMT
Keep-Alive: timeout=60
Connection: keep-alive

{
  "cause": {
    "cause": {
      "cause": null,
      "message": "Column 'task_id' cannot be null"
    },
    "message": "could not execute statement"
  },
  "message": "could not execute statement; SQL [n/a]; constraint [null]; nested exception is org.hibernate.exception.ConstraintViolationException: could not execute statement"
}

首先我创建了任务
已尝试向任务添加评论

如果我通过 id 获取任务：

GET http://localhost:9000/api/tasks/1
Accept: application/json

它会return它:

{
  "title": "new task",
  "description": "more content",
  "priority": "HIGH",
  "todoDate": "2020-07-02 10:50",
  "_links": {
    "self": {
      "href": "http://localhost:9000/api/tasks/1"
    },
    "task": {
      "href": "http://localhost:9000/api/tasks/1"
    }
  }
}

我做错了什么？我应该使用双向方法并将@OneToMany 添加到任务实体还是可以以某种方式配置？

Answer 1

从 task

中删除 @JsonIgnore

public class Comment {

    @ManyToOne(fetch = FetchType.LAZY, optional = false)
    @JoinColumn(name = "task_id", nullable = false)
    @OnDelete(action = OnDeleteAction.CASCADE)
    // @JsonIgnore
    private Task task;
}

和POST这个：

{
  "comment": "Some text",
  "task": "http://localhost:9000/api/tasks/1"
}

Answer 2

对于简单的 ManyToOne

@ManyToOne(fetch = FetchType.EAGER, optional = false)
@OnDelete(action = OnDeleteAction.CASCADE)
@JsonIgnore
private Task task;

我做了 fetch = FetchType.EAGER（lazy fetch 只获取特定的值 table，如果我们也想要映射的实体值，则使用 eager），并删除了 @JoinColumn（hibernate by默认在评论 table),

中创建字段“task_id”

我的 Json 评论对象是，

{
   "comment": "Some text",
   "task": {
          "id":1
    }
}

如何 POST 引用另一个 table 的新记录

How to POST a new record which is referenced to another table

spring

spring-data-rest

spring-boot