树状映射

这种方案固定、通用，下面以公司组织结构为例，要实现的树状图如图所示：

Org 组织类：

package com.bjsxt.hibernate;

import java.util.HashSet;
import java.util.Set;

import javax.persistence.CascadeType;
import javax.persistence.Entity;
import javax.persistence.FetchType;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;
import javax.persistence.JoinColumn;
import javax.persistence.ManyToOne;
import javax.persistence.OneToMany;

@Entity
public class Org {
    
    //节点id
    private int id;
    
    //节点名
    private String name;
    
    private Set<Org> children = new HashSet<Org>();
    
    private Org parent;

    @Id
    @GeneratedValue
    public int getId() {
        return id;
    }

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

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    //cascade=CascadeType.ALL    CUD操作能级联添加、更新、删除
    //mappedBy="parent"          以Org的parent属性为准
    //fetch=FetchType.EAGER      设置为 EAGER 模式，马上该对象的所有属性，而不是懒加载
    @OneToMany(cascade=CascadeType.ALL,mappedBy="parent",fetch=FetchType.EAGER)
    public Set<Org> getChildren() {
        return children;
    }

    public void setChildren(Set<Org> children) {
        this.children = children;
    }

    //ManyToOne 多个子节点对应一个父节点
    //JoinColumn(name="parent_id") 外键的字段名：parent_id
    @ManyToOne
    @JoinColumn(name="parent_id")
    public Org getParent() {
        return parent;
    }

    public void setParent(Org parent) {
        this.parent = parent;
    }
}

保存和获取节点：

@Test
    public void testSave(){
        //设置节点结构
        Org org = new Org();
        org.setName("总公司");
        Org org1 = new Org();
        org1.setName("分公司1");
        Org org2 = new Org();
        org2.setName("分公司2");
        Org org11 = new Org();
        org11.setName("分公司1下部门1");
        Org org12 = new Org();
        org12.setName("分公司1下部门2");
        
        org.getChildren().add(org1);
        org.getChildren().add(org2);
        org1.getChildren().add(org11);
        org1.getChildren().add(org12);
        org11.setParent(org1);
        org12.setParent(org1);
        org1.setParent(org);
        org2.setParent(org);
        
        Session session = sf.getCurrentSession();
        session.beginTransaction();
        //因为配置了cascade=CascadeType.ALL能够进行级联更新，所以只要保存根节点就能插入所有的子节点
        session.save(org);
        session.getTransaction().commit();
    }
    
    @Test
    public void testLoad(){
        testSave();
        
        Session session = sf.getCurrentSession();
        session.beginTransaction();
        Org org = (Org) session.load(Org.class, 1);
        //递归输出所有节点
        print(org,0);
        session.getTransaction().commit();
    }
    
    //输出方法
    private void print(Org org,int level) {
        String preStr = "";
        for(int i=0;i<level;i++){
            preStr += "----|";
        }
        
        System.out.println(preStr + org.getName());
        for(Org o:org.getChildren()){
            //如果有子节点，则继续往下递归
            print(o,level+1);
        }
    }

jar包链接: https://pan.baidu.com/s/1gf9nQoV 密码: 3uvj

代码链接: https://pan.baidu.com/s/1i4CXylf 密码: 8uau