Question

尝试使用Spring Data Rest：

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;
}

我无法添加应与1个任务相关联的新评论

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

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

此请求返回：

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
试图在任务中添加评论

如果我通过ID获得任务：

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

它将返回它：

{
  "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"
    }
  }
}

我在做什么错？我应该使用双向方法并将@OneToMany添加到Task实体还是以某种方式可配置？

Answer 1

从@JsonIgnore删除task

public class Comment {

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

并发布：

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

Answer 2

简单的ManyToOne

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

我制作了fetch = FetchType.EAGER（延迟获取仅获取特定表中的值，如果我们还希望使用映射的实体值，那么将使用eager），然后将其删除@JoinColumn（默认情况下，hibernate在其中创建字段“ task_id”评论表），

我对评论的Json对象是

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

如何过帐引用到另一个表的新记录

2 个答案: