如何在Hibernate中定义复合外键映射？ [英] How to define composite foreign key mapping in hibernate?

问题描述

我有两个表：USERS和USERDILES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

}

用户详细信息类如下：

public class UserDetails implements Serializable{

int id;

String name;

String address;

String otherFields;

//getters and setters

}

USERS中的id和name是一个复合主键，我希望用户详细信息中的相同字段作为外键。如何在休眠中实现这一点？

推荐答案

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

映射这两个主键

Composite Primary Key有两个选项：

1. 使用@EmbeddedId
2. 使用@IdClass()

下面是示例：

-----------------------------------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
}

用户详细信息：

@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
}

用户详细信息：

@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
}

->；如果要手动插入两个外键，请尝试下面的代码

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：

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