具有 JoinTable 关系的 ManyToOne 无法正常工作

Question

我有一个部门实体，一个部门最多只能有一个地址，一个地址也是一个实体，可以在多个部门之间共享。

为了在休眠中练习 ManyToOne 关系，我决定有一个 JoinTable，这是我的实体定义：

import lombok.Getter;
import lombok.Setter;

import javax.persistence.*;

@Getter
@Setter
@Entity(name = "Address")
public class Address {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;

    @Column(name = "name")
    private String city;
}

地址实体：

@Getter
@Setter
@Entity(name = "department")
public class Department {

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

    private String name;

    @ManyToOne
    @JoinColumn(name = "person_id")
    private Person manager;


    // many departments can have the same address
    // one department should have at most one address
    // todo not working as expected, we are not fetching the address of the department
    @ManyToOne(fetch = FetchType.EAGER)
    @JoinTable(name = "department_address",
            joinColumns = @JoinColumn(name = "address_id", referencedColumnName = "id"),
            inverseJoinColumns = @JoinColumn(name = "department_id", referencedColumnName = "id"))
    private Address address;
}

Person 实体（为示例的完整性而添加）：

@Getter
@Setter
@Entity(name = "person")
public class Person {

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

    private String name;

    @OneToOne(cascade = CascadeType.ALL)
    @JoinColumn(name = "address_id")
    private Address address;
}

当使用 spring 数据 jpa 从数据库中检索部门时，就好像我们没有获取与部门关联的地址数据。

这里是数据库的内容：

Table部门

id	name	person_id
23	IT	3

Table地址

id	name
2	Paris
3	kharajiv

Table department_address

id	address_id	department_id
2	2	23

存储库定义：

public interface DepartmentRepository extends JpaRepository<Department, Long> {}

查找给定部门时，以我为例，它是部门 23，departments/23:

Department department = departmentRepository.findById(id).get();
Address address = department.getAddress();
System.out.println("address = " + address);

地址始终为空，即使对于部门 23，table department_address 中有一行，这里是部门

的输出

System.out.println("department = " + department);
department = Department(id=23, name=IT, manager=Person(id=3, name=hamida, address=Address(id=3, city=kharajiv)), address=null)

这是打印的 sql 查询：

Hibernate: select department0_.id as id1_1_0_, department0_.person_id as person_i3_1_0_, department0_.name as name2_1_0_, department0_1_.department_id as departme1_2_0_, person1_.id as id1_3_1_, person1_.address_id as address_3_3_1_, person1_.name as name2_3_1_, address2_.id as id1_0_2_, address2_.name as name2_0_2_, address3_.id as id1_0_3_, address3_.name as name2_0_3_ from department department0_ left outer join department_address department0_1_ on department0_.id=department0_1_.address_id left outer join person person1_ on department0_.person_id=person1_.id left outer join Address address2_ on person1_.address_id=address2_.id left outer join Address address3_ on department0_1_.department_id=address3_.id where department0_.id=?

Answer 1

@JoinTable注解用于指定many-to-manytable关系的映射。在这种情况下使用@ManyToMany

Answer 2

左外连接地址 address3_ on department0_1_.department_id=address3_.id whe

可能我看错了，deparment id和address id不匹配。必须是 deparment0_1.address_id = address3_.id

能否尝试将 inversecolumn 更改为 address_id

joinColumns = @JoinColumn(name = "deparment_id", referencedColumnName = "id"),
            inverseJoinColumns = @JoinColumn(name = "address_id", referencedColumnName = "id"))
    private Address address

Answer 3

joinColumns：分配与实体（在您的案例中为部门）相关的第三个table 列。 inverseJoinColumns：分配第三列table与关联实体（您的情况下的地址）相关。

你的反了。您在 inverseJoinColumns 中拥有实体（部门），在 joinColumns

中拥有地址

JoinTable Documentation

具有 JoinTable 关系的 ManyToOne 无法正常工作

ManyToOne with JoinTable relationship doesn't work properly

java

hibernate

spring-data-jpa