jpa复合主键的使用

package com.ljq.entity;

import javax.persistence.Column;
import javax.persistence.Embeddable;

/**
* 使用复合主键要满足的条件
*
* 1、要实现序列化 2、提供默认的构造方法 3、实现hashCope
*
* @author Administrator
*
*/

@SuppressWarnings("serial")
@Embeddable  //embeddable: 可嵌入的
public class AirLinePk implements java.io.Serializable {
@Column(length = 3)
private String startCity;// 出发城市

@Column(length = 3)
private String endCity;// 抵达城市

public AirLinePk() {
super();
}

public AirLinePk(String startCity, String endCity) {
super();
this.startCity = startCity;
this.endCity = endCity;
}

public String getEndCity() {
return endCity;
}

public void setEndCity(String endCity) {
this.endCity = endCity;
}

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;
}

}

package com.ljq.entity;

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

@SuppressWarnings("serial")
@Entity
public class AirLine implements java.io.Serializable{
@EmbeddedId
private AirLinePk id;

@Column(length=20)
private String name;

public AirLine() {
super();
}

public AirLine(String startCity,String endCity, String name) {
this.id =new AirLinePk(startCity,endCity);
this.name = name;
}

public AirLinePk getId() {
return id;
}

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

public String getName() {
return name;
}

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

}

package com.ljq.test;

import java.util.List;

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

import org.junit.Test;

import com.ljq.entity.AirLine;
import com.ljq.entity.AirLinePk;

public class PKTest {

@Test
public void save() {
EntityManagerFactory factory = Persistence.createEntityManagerFactory("ljq");
EntityManager em=factory.createEntityManager();
em.getTransaction().begin();

em.persist(new AirLine("PEK","SHA","北京飞上海"));

em.getTransaction().commit();
em.close();
factory.close();

}

@Test
public void find() {
EntityManagerFactory factory = Persistence.createEntityManagerFactory("ljq");
EntityManager em=factory.createEntityManager();
em.getTransaction().begin();

AirLine airLine=em.find(AirLine.class, new AirLinePk("PEK","SHA"));
System.out.println(airLine.getName());

em.getTransaction().commit();
em.close();
factory.close();

}

@Test
public void update() {
EntityManagerFactory factory = Persistence.createEntityManagerFactory("ljq");
EntityManager em=factory.createEntityManager();
em.getTransaction().begin();

AirLine airLine=em.getReference(AirLine.class, new AirLinePk("PEK","SHA"));
airLine.setName("北京飞上海北京飞上海");
em.merge(airLine);

em.getTransaction().commit();
em.close();
factory.close();

}

@SuppressWarnings({ "unused", "unchecked" })
@Test
public void list() {
EntityManagerFactory factory = Persistence.createEntityManagerFactory("ljq");
EntityManager em=factory.createEntityManager();
em.getTransaction().begin();

List<AirLine> airLines=em.createQuery("select o from AirLine o").getResultList();
for(AirLine air:airLines){
System.out.println(air.getName());
}

em.getTransaction().commit();
em.close();
factory.close();

}

@SuppressWarnings({ "unused", "unchecked" })
@Test
public void detele() {
EntityManagerFactory factory = Persistence.createEntityManagerFactory("ljq");
EntityManager em=factory.createEntityManager();
em.getTransaction().begin();

em.remove(em.getReference(AirLine.class, new AirLinePk("PEK","SHA")));

em.getTransaction().commit();
em.close();
factory.close();

}

/**
* 用来判断映射是否成功
*
*/
@Test
public void test() {
Persistence.createEntityManagerFactory("ljq");
}

}