Hibernate之复合主键映射

一,概述

复合主键也是开发中经常遇到的需求,这篇博客就是关于复合主键映射,开始吧!

二,实体类准备

1)复合主键类

package com.bighuan.d_compositeKey;

import java.io.Serializable;

/**
 * 复合主键类:用户名和地址唯一标识一条记录
 * 
 * @author bighuan
 * 
 */
public class CompositeKeys implements Serializable {

	private String userName;
	private String address;

	public CompositeKeys() {

	}

	public String getUserName() {
		return userName;
	}

	public void setUserName(String userName) {
		this.userName = userName;
	}

	public String getAddress() {
		return address;
	}

	public void setAddress(String address) {
		this.address = address;
	}

}

2)表对应的实体类User.java

package com.bighuan.d_compositeKey;

public class User {

	public User() {

	}

	private int age;

	private CompositeKeys keys;

	public int getAge() {
		return age;
	}

	public void setAge(int age) {
		this.age = age;
	}

	public CompositeKeys getKeys() {
		return keys;
	}

	public void setKeys(CompositeKeys keys) {
		this.keys = keys;
	}

}

三,配置文件准备

1)User.java对应的映射文件User.hbm.xml

<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC 
	"-//Hibernate/Hibernate Mapping DTD 3.0//EN"
	"http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd">

<hibernate-mapping package="com.bighuan.d_compositeKey"
	auto-import="true">

	<class name="User">
		<!-- 复合主键映射 -->
		<composite-id name="keys">
			<key-property name="userName" type="string"></key-property>
			<key-property name="address" type="string"></key-property>
		</composite-id>

		<property name="age" type="int"></property>

	</class>

</hibernate-mapping>

配置复合主键主要是通过<composite-id>来完成!

2)hibernate.cfg.xml(上一篇博客粘贴过这个文件,多复制一遍,加深印象)

<!DOCTYPE hibernate-configuration PUBLIC
	"-//Hibernate/Hibernate Configuration DTD 3.0//EN"
	"http://www.hibernate.org/dtd/hibernate-configuration-3.0.dtd">

<hibernate-configuration>
	<session-factory>
		<!--1, 数据库连接配置 -->
		<property name="hibernate.connection.driver_class">com.mysql.jdbc.Driver</property>
		<property name="hibernate.connection.url">jdbc:mysql://localhost:3306/hib_demo</property>
		<property name="hibernate.connection.username">root</property>
		<property name="hibernate.connection.password">abc</property>
		
		<!--2, 数据库方法配置:告诉hibernate使用的是什么数据库 -->
		<!-- hibernate在运行的时候,会根据不同的方言生成符合当前数据库语法的sql -->
		<property name="hibernate.dialect">org.hibernate.dialect.MySQL5Dialect</property>
		<!--3, 其他相关配置:3.1展示hibernate在运行时执行的sql语句-->
		<property name="hibernate.show_sql">true</property>
		
		<!-- 3.2格式化sql语句配置 -->
		<property name="hibernate.format_sql">true</property>

               <!-- 3.3自动建表 ,先删除后创建,不管有没有表-->
		<!-- <property name="hibernate.hbm2ddl.auto">create</property> -->
		
		<!-- 3.4有表就不创建,反之就创建 -->
		<property name="hibernate.hbm2ddl.auto">update</property> 
		
		<!--映射配置:  加载所有映射 -->
		<mapping resource="com/bighuan/d_compositeKey/User.hbm.xml"/>
	</session-factory>
</hibernate-configuration>

四,测试

1)插入数据,查询数据

package com.bighuan.d_compositeKey;

import java.util.Date;

import org.hibernate.SessionFactory;
import org.hibernate.Transaction;
import org.hibernate.cfg.Configuration;
import org.junit.Test;

public class App2 {

	private static SessionFactory sf = null;
	static {

		sf = new Configuration().configure().buildSessionFactory();
	}

	@Test
	public void testSave() throws Exception {
		// 创建对象
		CompositeKeys keys = new CompositeKeys();
		keys.setUserName("bighuan");
		keys.setAddress("江西南昌2");
		User user = new User();
		user.setAge(25);
		user.setKeys(keys);

		// 创建session(代表一个与数据库连接的会话)
		org.hibernate.Session session = sf.openSession();
		// 4,开启事务
		Transaction tx = session.beginTransaction();
		// 5,保存数据
		session.save(user);

		tx.commit();
		// 7,关闭
		session.close();
	}

	@Test
	public void testQuery() throws Exception {
		// 创建对象
		CompositeKeys keys = new CompositeKeys();
		keys.setUserName("bighuan");
		keys.setAddress("江西南昌");

		// 创建session(代表一个与数据库连接的会话)
		org.hibernate.Session session = sf.openSession();
		// 4,开启事务
		Transaction tx = session.beginTransaction();
		// 5,查询数据
		User user = (User) session.get(User.class, keys);

		if (user != null) {
			System.out.println(user.getAge() + ","
					+ user.getKeys().getAddress() + ","
					+ user.getKeys().getUserName());
		}

		tx.commit();
		// 7,关闭
		session.close();
	}

}

2)插入两条数据到数据库,数据库的user表

3)通过主键查询

25,江西南昌,bighuan