如何在hibernate中定义复合外键映射？

Question

我有两个表：users和userdetails如下：

package com.example.easynotes.model;

import javax.persistence.*;
import java.io.Serializable;

@Entity
@Table(name = "users")
@IdClass(UserID.class)
public class User implements Serializable {

    @Id
    int id;

    @Id
    String name;

    String department;

    //getters and setters

}

userdetails 类是这样的：

public class UserDetails implements Serializable{

int id;

String name;

String address;

String otherFields;

//getters and setters

}

users 中的 id 和 name 是复合主，我希望 userdetails 中的相同字段成为外键。如何在休眠中实现这一点？

Answer 1

我们需要将两个键都放入@Embeddable 以分离复合键，然后使用@EmbeddedId 将其放入User 实体中并使用Hibernate Relational Mapping 映射两个主键...

Composite Primary Key有两种选择：

1. 使用@EmbeddedId
2. 使用@IdClass()

下面是例子：

---------------------- 使用 EmbeddedId -------- ----------------------------------------

复合主键：

@Embeddable
public class UserIdName implements Serializable {
    int id;
    String name;
    
    // getter and setter
}

用户：

@Entity
@Table(name = "users")
public class USER{
    @EmbeddedId
    private UserIdName id;

    String department;
    
    @OneToMany(cascade = CascadeType.ALL, mappedBy = "user")
    private Set<Userdetail> userdetail;

    // getter and setter
}

用户详情：

@Entity
@Table(name = "Userdetail")
public class Userdetail {

    @Id
    private int detail_id;

    @ManyToOne
    @JoinColumns({ @JoinColumn(name = "id", referencedColumnName = "id"),
            @JoinColumn(name = "name", referencedColumnName = "name") })
    private USER user;

    String address;

    String otherFields;

    // getter setter
}

---------------------- 使用 IdClass -------- ----------------------------------------

复合主键：

public class UserIdName implements Serializable {
    int id;
    String name;
    
    // getter and setter
}

用户：

@Entity
@Table(name = "users")
@IdClass(UserIdName.class)
public class USER{
    @Id
    int id;

    @Id
    String name;

    String department;
    
    @OneToMany(cascade = CascadeType.ALL, mappedBy = "user")
    private Set<Userdetail> userdetail;

    // getter and setter
}

用户详情：

@Entity
@Table(name = "Userdetail")
public class Userdetail {

    @Id
    private int detail_id;

    @ManyToOne
    @JoinColumns({ @JoinColumn(name = "id", referencedColumnName = "id"),
            @JoinColumn(name = "name", referencedColumnName = "name") })
    private USER user;

    String address;

    String otherFields;

    // getter setter
}

->如果您想手动插入两个外键，请尝试以下代码

将此代码放入UserDetails

@ManyToOne
@JoinColumn(name = "id", referencedColumnName = "id", insertable = false, updatable = false)
@JoinColumn(name = "name", referencedColumnName = "name", insertable = false, updatable = false)
private USER user;

@Column(name="id")
private int id;

@Column(name="name")
private String name

// don't forget to put getter setter

用户表：

用户明细表：