JPA学习总结（五）--JPACompositePK联合主键

步骤1.新建java项目：JPACompositePK，将hibernate包以及mysql驱动包导入

 

 

 

步骤2.在类路径下新建xml文件persistence.xml，将其放入META-INF文件夹下，其代码如下：

 

 

<?xml version="1.0" encoding="UTF-8"?>
<persistence xmlns="http://java.sun.com/xml/ns/persistence"
	xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
	xsi:schemaLocation="http://java.sun.com/xml/ns/persistence http://java.sun.com/xml/ns/persistence/persistence_1_0.xsd"
	version="1.0">
	<persistence-unit name="itcast" transaction-type="RESOURCE_LOCAL">
		<properties>
		
			<property name="hibernate.connection.url" value="jdbc:mysql://localhost:3306/itcast?useUnicode=true&amp;characterEncoding=UTF-8" />
			<property name="hibernate.dialect" value="org.hibernate.dialect.MySQL5Dialect"/>	
			<property name="hibernate.connection.driver_class" value="org.gjt.mm.mysql.Driver" />
			<property name="hibernate.connection.username" value="root" />
			<property name="hibernate.connection.password" value="root" />
			<property name="hibernate.max_fetch_depth" value="3" />
			<property name="hibernate.hbm2ddl.auto" value="update" />
		</properties>
	</persistence-unit>
</persistence>

 

 

 

 

 

 

 

步骤3.编写实体Bean类

 

AirLinePK代码如下：

 

package cn.itcast.bean;

import java.io.Serializable;

import javax.persistence.Column;
import javax.persistence.Embeddable;
/**
 * 联合主键的要求：
 * 1.要求无参数的构造函数
 * 2.实现Serializable接口
 * 3.重写hashCode（）和equals（）方法
 */
@Embeddable//在实体里面只使用该类的属性，作为实体的持久化属性
public class AirLinePK implements Serializable{
	private static final long serialVersionUID = 362881507756738676L;
	private String startCity;//PEK(北京），SHA(上海)
	private String endCity;
	
	public AirLinePK(){}
	
	public AirLinePK(String startCity, String endCity) {
		this.startCity = startCity;
		this.endCity = endCity;
	}
	@Column(length=3,nullable=false)
	public String getEndCity() {
		return endCity;
	}
	public void setEndCity(String endCity) {
		this.endCity = endCity;
	}
	@Column(length=3,nullable=false)
	public String getStartCity() {
		return startCity;
	}
	public void setStartCity(String startCity) {
		this.startCity = startCity;
	}
	@Override
	public int hashCode() {
		final int PRIME = 31;
		int result = 1;
		result = PRIME * result + ((endCity == null) ? 0 : endCity.hashCode());
		result = PRIME * result + ((startCity == null) ? 0 : startCity.hashCode());
		return result;
	}
	@Override
	public boolean equals(Object obj) {
		if (this == obj)
			return true;
		if (obj == null)
			return false;
		if (getClass() != obj.getClass())
			return false;
		final AirLinePK other = (AirLinePK) obj;
		if (endCity == null) {
			if (other.endCity != null)
				return false;
		} else if (!endCity.equals(other.endCity))
			return false;
		if (startCity == null) {
			if (other.startCity != null)
				return false;
		} else if (!startCity.equals(other.startCity))
			return false;
		return true;
	}
	
}

 

 

 

 

 

 

 

 

AirLine代码如下： 

 

package cn.itcast.bean;

import javax.persistence.Column;
import javax.persistence.EmbeddedId;
import javax.persistence.Entity;

@Entity
public class AirLine {
	private AirLinePK id;
	private String name;
	
	public AirLine(){}
	
	public AirLine(String startCity,String endCity,String name) {
		this.id = new AirLinePK(startCity,endCity);
		this.name = name;
	}
	@EmbeddedId//复合主键的主键标注
	public AirLinePK getId() {
		return id;
	}
	public void setId(AirLinePK id) {
		this.id = id;
	}
	@Column(length=20)
	public String getName() {
		return name;
	}
	public void setName(String name) {
		this.name = name;
	}
	
	
}

 

 

 

步骤4.创建junit测试：

 

package junit.test;


import javax.persistence.EntityManager;
import javax.persistence.EntityManagerFactory;
import javax.persistence.Persistence;

import org.junit.BeforeClass;
import org.junit.Test;

import cn.itcast.bean.AirLine;

public class AirLineTest {

	@BeforeClass
	public static void setUpBeforeClass() throws Exception {
	}

	@Test public void save(){
		EntityManagerFactory factory = Persistence.createEntityManagerFactory("itcast");
		EntityManager em = factory.createEntityManager();
		em.getTransaction().begin();
		AirLine line = new AirLine("SHA","PEK","上海飞北京");
		em.persist(line);		
		em.getTransaction().commit();
		em.close();
		factory.close();
	}
}

 

 

 

 

 

 

 看能将表创建出来，并插入数据即可。