Hibernate联合主键

话不多说,直接上demo:

 现在又一个model类:用于做组员和分组的映射,是有两字段:uid和gid(均为主键),此时如果要引入Hibernate,则需要一下步骤:

1.将uid和gid抽离出来作为一个独立类:

package model;

import java.io.Serializable;

import javax.persistence.Embeddable;

@Embeddable
public class u_g_id implements Serializable{

    private int uid;
    private int gid;
    
    public u_g_id() {
        super();
    }
    
    public u_g_id(int uid, int gid) {
        this.uid = uid;
        this.gid = gid;
    }
    public int getUid() {
        return uid;
    }
    public void setUid(int uid) {
        this.uid = uid;
    }
    
    public int getGid() {
        return gid;
    }
    public void setGid(int gid) {
        this.gid = gid;
    }
    
    @Override
    public boolean equals(Object o) {
        if(o instanceof u_g_id) {
            u_g_id pk = (u_g_id)o;
            if(this.uid == pk.getUid() && this.gid == (pk.getGid())) {
              return true;
            }
        }
        return false;
    }
    @Override
    public int hashCode() {
        return super.hashCode();
    }
    
}

重点:1.@Embeddable标签

       2.必须重写equals和hashcode方法

 

2.在user_group类中引用这个类:

package model;

import javax.persistence.Entity;
import javax.persistence.Id;

@Entity
public class user_group {

    private u_g_id id;

    @Id
    public u_g_id getId() {
        return id;
    }

    public void setId(u_g_id id) {
        this.id = id;
    }
    
    
    
}

然后就可以使用联合主键了:

public boolean addMember(int uid,int gid){
        Session s = this.getSession();
        s.beginTransaction();
        try{
            user_group ug = new user_group();
            ug.setId(new u_g_id(uid,gid));
            s.save(ug);
            s.getTransaction().commit();
        }catch(Exception e){
            s.getTransaction().rollback();
            return false;
        }
        return true;
    }