sql - 使用 Hibernate 插入嵌套实体

问题描述

我试图弄清楚如何正确地将几个实体插入到数据库中，这些实体具有另一个实体作为字段，并且似乎在休眠中它是一个不简单的任务。当我把所有东西都整理整齐时它工作得很好，但是一旦它们交叉链接，它就不能按预期工作。我假设我缺少一些必需的注释以使其正常工作，但是经过几个小时的谷歌搜索，我找不到任何合适的方法来迅速解决它。

我当前的实体以这种方式设置我有一个学生和

@Entity
@Data
@NoArgsConstructor
@AllArgsConstructor
public class Student {

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private int id;
    private String name;
}

我有一个教室，里面有一个学生实体，通过它的 id 链接

@Entity
@Data
@NoArgsConstructor
@AllArgsConstructor
public class ClassRoom {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;

    @ManyToOne(fetch = FetchType.LAZY)
    @JoinColumn(name = "student_id", foreignKey = @ForeignKey(name = "fk_student"))
    private Student student;

    private String dateCreated;
}

当我尝试将它存储到数据库中时，我有一个完美的 json：

{
   "dateCreated":"17",
   "body":[
      {
         "id":1,
         "student":{
            "id":1,
            "name":"petya",
            "hibernateLazyInitializer":{

            }
         },
         "dateCreated":"17"
      },
      {
         "id":2,
         "student":{
            "id":2,
            "name":"petrya",
            "hibernateLazyInitializer":{

            }
         },
         "dateCreated":"17"
      },
      {
         "id":3,
         "student":{
            "id":3,
            "name":"slon",
            "hibernateLazyInitializer":{

            }
         },
         "dateCreated":"17"
      }
   ]
}

Hibernate: select student0_.id as id1_1_0_, student0_.name as name2_1_0_ from json_schema.student student0_ where student0_.id=?
Hibernate: select student0_.id as id1_1_0_, student0_.name as name2_1_0_ from json_schema.student student0_ where student0_.id=?
Hibernate: select student0_.id as id1_1_0_, student0_.name as name2_1_0_ from json_schema.student student0_ where student0_.id=?
Hibernate: select classroom0_.id as id1_0_0_, classroom0_.date_created as date_cre2_0_0_, classroom0_.student_id as student_3_0_0_ from json_schema.class_room classroom0_ where classroom0_.id=?
Hibernate: select classroom0_.id as id1_0_0_, classroom0_.date_created as date_cre2_0_0_, classroom0_.student_id as student_3_0_0_ from json_schema.class_room classroom0_ where classroom0_.id=?
Hibernate: select classroom0_.id as id1_0_0_, classroom0_.date_created as date_cre2_0_0_, classroom0_.student_id as student_3_0_0_ from json_schema.class_room classroom0_ where classroom0_.id=?
Hibernate: update json_schema.class_room set date_created=?, student_id=? where id=?
Hibernate: update json_schema.class_room set date_created=?, student_id=? where id=?
Hibernate: update json_schema.class_room set date_created=?, student_id=? where id=?

但是一旦我尝试保存链接到第三个学生的第二个教室条目，例如这个：

{
   "dateCreated":"10",
   "body":[
      {
         "id":1,
         "student":{
            "id":1,
            "name":"petya",
            "hibernateLazyInitializer":{

            }
         },
         "dateCreated":"10"
      },
      {
         "id":2,
         "student":{
            "id":3,
            "name":"slon",
            "hibernateLazyInitializer":{

            }
         },
         "dateCreated":"10"
      },
      {
         "id":3,
         "student":{
            "id":2,
            "name":"petrya",
            "hibernateLazyInitializer":{

            }
         },
         "dateCreated":"10"
      }
   ]
}

Hibernate: select student0_.id as id1_1_0_, student0_.name as name2_1_0_ from json_schema.student student0_ where student0_.id=?
Hibernate: insert into json_schema.student (name) values (?)
Hibernate: select student0_.id as id1_1_0_, student0_.name as name2_1_0_ from json_schema.student student0_ where student0_.id=?
Hibernate: insert into json_schema.student (name) values (?)
Hibernate: update json_schema.student set name=? where id=?
Hibernate: select classroom0_.id as id1_0_0_, classroom0_.date_created as date_cre2_0_0_, classroom0_.student_id as student_3_0_0_ from json_schema.class_room classroom0_ where classroom0_.id=?
Hibernate: insert into json_schema.class_room (date_created, student_id) values (?, ?)
Hibernate: select classroom0_.id as id1_0_0_, classroom0_.date_created as date_cre2_0_0_, classroom0_.student_id as student_3_0_0_ from json_schema.class_room classroom0_ where classroom0_.id=?
Hibernate: insert into json_schema.class_room (date_created, student_id) values (?, ?)

它打破了：

错误：在表“class_room”上插入或更新违反了外键约束“fk_student”详细信息：表“student”中不存在键 (student_id)=(3)。

这可能是我正在实现的逻辑，我试图以这种方式存储它们：

final ClassRoom[] classRooms = objectMapper.readValue(parser, ClassRoom[].class);
        final List<ClassRoom> classRoomList = Arrays.asList(classRooms);
        final List<Student> studentsList = new ArrayList<>();
        for (final ClassRoom classRoom : classRoomList) {
            studentsList.add(classRoom.getStudent());

        }
        studentRepo.saveAll(studentsList);
        classRoomRepo.saveAll(classRoomList);

但我不知道如何首先单独存储学生，只有在存储classRooms之后。感谢任何帮助。希望会随着时间的推移解决它，如果是这样，我会自己发布一个答案。

标签： sqlhibernateannotationsentity

sql - 使用 Hibernate 插入嵌套实体

问题描述

解决方案

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