Hibernate 一对多自身双向关联关系 用于类别表的实现

分类：一对多自身双向关联关系

Java持久化类：

package com.hyy.hibernate.one_to_many.domain;
 
import java.util.HashSet;
import java.util.Set;
 
/**
 * 分类：一对多自身双向关联关系
 * User: HYY
 * Date: 13-12-13
 * Time: 下午7:32
 * To change this template use File | Settings | File Templates.
 */
public class Category {
    private Integer id;
    private String name;
    private Category parent;
    private Set<Category> children = new HashSet<Category>();
 
    public Integer getId() {
        return id;
    }
 
    public void setId(Integer id) {
        this.id = id;
    }
 
    public String getName() {
        return name;
    }
 
    public void setName(String name) {
        this.name = name;
    }
 
    public Category getParent() {
        return parent;
    }
 
    public void setParent(Category parent) {
        this.parent = parent;
    }
 
    public Set<Category> getChildren() {
        return children;
    }
 
    public void setChildren(Set<Category> children) {
        this.children = children;
    }
}

Category.hbm.xml

<?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="com.hyy.hibernate.one_to_many.domain">
 
    <class name="Category" dynamic-update="true">
 
        <id name="id">
            <generator class="native"/>
        </id>
 
        <property name="name" length="50" access="property"/>
 
        <many-to-one name="parent" column="parent_id" />
 
        <set name="children" inverse="true" cascade="save-update" lazy="true">
            <key column="parent_id"/>
            <one-to-many class="Category"/>
        </set>
 
    </class>
 
</hibernate-mapping>

一对多关联关系的one-to-many和many-to-one标签中的外键名要相同，比如本例的parent_id，一定是这两个，不能是其他了。

测试类：

public class CategoryTest {
 
    @Test
    public void test1() {
        //食物
        Category food = new Category();
        food.setName("food");
 
        //水果
        Category fruit = new Category();
        fruit.setName("fruit");
        fruit.setParent(food);
        food.getChildren().add(fruit);
 
        //蔬菜
        Category veg = new Category();
        veg.setName("veg");
        veg.setParent(food);
        food.getChildren().add(veg);
 
        //苹果
        Category apple = new Category();
        apple.setName("apple");
        apple.setParent(fruit);
        fruit.getChildren().add(apple);
 
        Session session = HibernateUtil.getSession();
        session.beginTransaction();
        session.save(food);
        session.getTransaction().commit();
    }
}