springboot JPA 聯合主鍵

一、聯合主鍵類JPA規范

1、必須提供一個public的無參數構造函數；

2、必須實現序列化接口；

3、必須重寫hashCode()和equals()這兩個方法。這兩個方法應該采用復合主鍵的字段作為判斷這個對象是否相等的；

4、聯合主鍵類的類名結尾一般要加上PK兩個字母代表一個主鍵類，不是要求而是一種命名風格;

5、getter、setter etc 

package com.DotSDot.pojo;

import java.io.Serializable;
import java.util.Objects;

/**
 * @author Predator
 * @create 2020-10-05-10:18 AM
 */
public class RolePermissionInformationPK implements Serializable {
    private String role_id;
    private String permission_id;

    public RolePermissionInformationPK() {
    }

    public RolePermissionInformationPK(String role_id, String permission_id) {
        this.role_id = role_id;
        this.permission_id = permission_id;
    }

    @Override
    public boolean equals(Object o) {
        if (this == o) return true;
        if (o == null || getClass() != o.getClass()) return false;
        RolePermissionInformationPK that = (RolePermissionInformationPK) o;
        return Objects.equals(role_id, that.role_id) &&
                Objects.equals(permission_id, that.permission_id);
    }

    @Override
    public int hashCode() {
        return Objects.hash(role_id, permission_id);
    }

    public String getRole_id() {
        return role_id;
    }

    public void setRole_id(String role_id) {
        this.role_id = role_id;
    }

    public String getPermission_id() {
        return permission_id;
    }

    public void setPermission_id(String permission_id) {
        this.permission_id = permission_id;
    }
}

二、實體類

1、@IdClass(PK.class)

2、@Id

package com.DotSDot.pojo;

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

/**
 * @author Predator
 * @create 2020-10-05-8:46 AM
 */
@Entity
@Table(name = "tb_role_permissioninformation")
@IdClass(RolePermissionInformationPK.class)
public class RolePermissionInformation implements Serializable {
    @Id
    private String role_id;
    @Id
    private String permission_id;

    public String getRole_id() {
        return role_id;
    }

    public void setRole_id(String role_id) {
        this.role_id = role_id;
    }

    public String getPermission_id() {
        return permission_id;
    }

    public void setPermission_id(String permission_id) {
        this.permission_id = permission_id;
    }

    public RolePermissionInformation() {
    }

    public RolePermissionInformation(String role_id, String permission_id) {
        this.role_id = role_id;
        this.permission_id = permission_id;
    }
}