Hibernate基于配置文件（十一）多对一双向关联树形结构的映射

使用Hibernate建立树形结构

 

递归查询子节点，会发出N多次select查询

可以在Node中定义一个字段，额外记录其与parent的id间的关系，如1|3|6|12

然后使用like进行模糊查询，只需要查询1次即可找出所有的child。

虽然模糊查询慢，但只发出1条语句，所以效率可能比发出N多次递归查询快！

 

实体类

package org.leadfar.hibernate.model;

import java.util.Set;

public class Node {
	private int id;
	private String name;
	private Node parent;
	private Set<Node> children;//一的一端使用集合存储对方引用
	
	
	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;
	}
	public Node getParent() {
		return parent;
	}
	public void setParent(Node parent) {
		this.parent = parent;
	}
	public Set<Node> getChildren() {
		return children;
	}
	public void setChildren(Set<Node> children) {
		this.children = children;
	}
	
}

 

 

 映射文件

<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC 
	"-//Hibernate/Hibernate Mapping DTD 3.0//EN"
	"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<hibernate-mapping 
	package="org.hibernate.auction">
	<class name="org.leadfar.hibernate.model.Node" table="t_node" >
		<!-- id为数据库标识，作为主键 -->
		<id name="id">
			<generator class="native"/>
		</id>
		
		<property name="name"/>
		<many-to-one name="parent" column="pid"> </many-to-one>
		<set name="children" lazy="extra" inverse="true">
			<key column="pid"></key>
			<one-to-many class="org.leadfar.hibernate.model.Node"></one-to-many>
		</set>
	</class>
	
</hibernate-mapping>

 

 

测试

package org.leadfar.hibernate.model;
import java.io.File;
import java.util.Iterator;
import java.util.Set;

import junit.framework.TestCase;

import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.cfg.Configuration;

public class Test_tree extends TestCase {
	/**
	 * 建立一个文件目录树。可以根据某个节点查找其父节点，也可以查找其子节点
	 * 查找父节点--many-to-one
	 * 查找子节点--one-to-many
	 * 
	 * 关联关系---parent字段，可以看做是外键
	 * 从多的一端即孩子端建立关联关系
	 */
	public void tree_save() {
		Configuration cfg = new Configuration().configure();
		
		
		SessionFactory sfactory = cfg.buildSessionFactory();
		
		
		Session session = sfactory.openSession();
		
		try {
			
			session.beginTransaction();
			
			save(session,new File("F:\\oracle"),null);
			

			session.getTransaction().commit();
			
		} catch(Exception e) {
			e.printStackTrace();
			
			session.getTransaction().rollback();
		} finally {
			
			session.close();
		}
		
	}
	public void tree_findParent() {
		Configuration cfg = new Configuration().configure();
		
		
		SessionFactory sfactory = cfg.buildSessionFactory();
		
		
		Session session = sfactory.openSession();
		
		try {
			
			session.beginTransaction();
			

			
			Node node = (Node)session.load(Node.class, 2034);
			find_parent(node);
			
			session.getTransaction().commit();
			
		} catch(Exception e) {
			e.printStackTrace();
			
			session.getTransaction().rollback();
		} finally {
			
			session.close();
		}
		
	}
	public void tree_findChild() {
		Configuration cfg = new Configuration().configure();

		SessionFactory sfactory = cfg.buildSessionFactory();
		
		Session session = sfactory.openSession();
		
		try {
			
			session.beginTransaction();

			Node node = (Node)session.load(Node.class, 22);
			find_child(node,0);
			
			session.getTransaction().commit();
			
		} catch(Exception e) {
			e.printStackTrace();
			
			session.getTransaction().rollback();
		} finally {
			
			session.close();
		}
		
	}
	
	//保存一个文件目录树到数据库---parent记录父子关系
	private void save(Session session,File file,Node parent) {
		Node node = new Node();
		node.setName(file.getName());
		node.setParent(parent);
		
		session.save(node);
		
		if(file.exists()) {
			File[] f = file.listFiles();
			if(f!=null && f.length>0) {
				for(File sub : f) {
					if(sub.isDirectory())
						save(session,sub,node);
				}
			}
		}
	}
	
	//查找给定节点的父节点
	private void find_parent(Node node) {
		System.out.print(node.getName());
		Node parent = node.getParent();
		if(parent!=null) {
			System.out.print("-->");
			find_parent(parent);
		}
	}
	
	//给定节点查找其子节点
	private void find_child(Node node,int level) {
		for(int i=0;i<level;i++) {
			System.out.print("\t");
		}
		System.out.println(node.getName());
		Set<Node> childs = node.getChildren();
		if(childs.size()!=0) {
			for(Node n : childs){
				find_child(n,level+1);
			}
		}
	}
}