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项非平凡的任务。当我把所有东西都整齐有序时,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。我想我缺少一些使其工作所需的注释,但是经过几个小时的谷歌搜索后,我找不到任何适合及时解决它的方法。
我目前的实体是这样设置的 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,里面有一个由 ID 链接的学生实体
@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;
}
我有一个 json,当我尝试将它存储到 db 时,它运行良好:
{
"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课堂条目,例如这样的:
{
"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:插入或更新表“class_room”违反外键约束“fk_student”详细信息:表“student”中不存在键(student_id)=(3)。
这可能是我正在实施的逻辑,我正在尝试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);
但是我不知道如何先单独存储学生,然后才存储 classRooms。感谢任何帮助。希望能随着时间的推移解决它,如果是这样,我会自己发布答案。
您的 id 方法是@GeneratedValue(strategy = GenerationType.IDENTITY)
,而您的学生和教室列表都预先填充了 id。如果您想保留这些 id 以 json 形式出现,请删除@GeneratedValue(strategy = GenerationType.IDENTITY)
注释。
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