JPA复合主键案例

AirLine实体类

package com.jason.bean;import java.io.Serializable;import javax.persistence.Column;import javax.persistence.EmbeddedId;import javax.persistence.Entity;@Entitypublic class AirLine implements Serializable{private static final long serialVersionUID = -5617618540181055061L;private AirLinePk id;    private String name;    public AirLine() {        super();    }    public AirLine(String startCity,String endCity, String name) {        this.id =new AirLinePk(startCity,endCity);        this.name = name;    }        @EmbeddedId    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;    }    }

AirLinePk复合主键类

package com.jason.bean;import java.io.Serializable;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hashCode *  * @author jason *  */@Embeddable  //embeddable: 可嵌入的public class AirLinePk implements Serializable {private static final long serialVersionUID = 7102936569989834678L;private String startCity;// 出发城市    private String endCity;// 到达城市    public AirLinePk() {        super();    }    public AirLinePk(String startCity, String endCity) {        super();        this.startCity = startCity;        this.endCity = endCity;    }       @Column(length = 3)    public String getStartCity() {        return startCity;    }    public void setStartCity(String startCity) {        this.startCity = startCity;    }        @Column(length = 3)    public String getEndCity() {        return endCity;    }    public void setEndCity(String endCity) {        this.endCity = endCity;    }    @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;    }}

PKTest测试类

package junit.test;import java.util.List;import javax.persistence.EntityManager;import javax.persistence.EntityManagerFactory;import javax.persistence.Persistence;import org.junit.AfterClass;import org.junit.BeforeClass;import org.junit.Test;import com.jason.bean.AirLine;import com.jason.bean.AirLinePk;public class PKTest {private static EntityManagerFactory factory;private static EntityManager em;@BeforeClasspublic static void setUpBeforeClass() throws Exception { factory = Persistence.createEntityManagerFactory("jason"); em = factory.createEntityManager();     em.getTransaction().begin();}    @Test    public void save() {        em.persist(new AirLine("PEK","SHA","北京飞上海"));    }        @Test    public void find() {        AirLine airLine=em.find(AirLine.class, new AirLinePk("PEK","SHA"));        System.out.println(airLine.getName());    }        @Test    public void update() {        AirLine airLine=em.getReference(AirLine.class, new AirLinePk("PEK","SHA"));        airLine.setName("北京飞上海啊哈哈");        em.merge(airLine);    }        @SuppressWarnings("unchecked")@Test    public void list() {        List<AirLine> airLines=em.createQuery("select o from AirLine o").getResultList();        for(AirLine air:airLines){            System.out.println(air.getName());        }    }        @Test    public void detele() {        em.remove(em.getReference(AirLine.class, new AirLinePk("PEK","SHA")));    }    /**     * 用来判断映射是否成功     *      */    @Test    public void test() {        Persistence.createEntityManagerFactory("jason");    }        @AfterClasspublic static void tearDownAfterClass() throws Exception {    em.getTransaction().commit();        em.close();        factory.close();}}