1 package com.yl.demo1.bean.JointPK; 2  3 import java.io.Serializable; 4  5 import javax.persistence.Column; 6 import javax.persistence.Embeddable; 7  8 /** 9  * 在联合主键类中只是定义确定联合主键的字段即可10  * 联合主键类的规则11  *     1.必须包含一个无参的构造函数12  *     2.必须实现序列化接口13  *  3.必须重写hashCode和equals方法，而且equals方法的参数必须包括确定联合主键的所有字段14  * @author yul15  *16  *@Embeddable--告诉其它类，在使用AieLinePK时只是使用AieLinePK的属性作为实体的持久化属性17  */18 19 @Embeddable //嵌入20 public class AirLinePK implements Serializable {21     private String startCity;//航空中每个城市都有一个三位的字母标识符22     private String endCity;23     24     public AirLinePK(){}25     26     27     public AirLinePK(String startCity, String endCity) {28         this.startCity = startCity;29         this.endCity = endCity;30     }31     @Column(length=3)32     public String getStartCity() {33         return startCity;34     }35     public void setStartCity(String startCity) {36         this.startCity = startCity;37     }38     @Column(length=3)39     public String getEndCity() {40         return endCity;41     }42     public void setEndCity(String endCity) {43         this.endCity = endCity;44     }45     46     @Override47     public int hashCode() {48         final int prime = 31;49         int result = 1;50         result = prime * result + ((endCity == null) ? 0 : endCity.hashCode());51         result = prime * result52                 + ((startCity == null) ? 0 : startCity.hashCode());53         return result;54     }55     @Override56     public boolean equals(Object obj) {57         if (this == obj)58             return true;59         if (obj == null)60             return false;61         if (getClass() != obj.getClass())62             return false;63         AirLinePK other = (AirLinePK) obj;64         if (endCity == null) {65             if (other.endCity != null)66                 return false;67         } else if (!endCity.equals(other.endCity))68             return false;69         if (startCity == null) {70             if (other.startCity != null)71                 return false;72         } else if (!startCity.equals(other.startCity))73             return false;74         return true;75     }76     77     78 }

 1 package com.yl.demo1.bean.JointPK; 2  3 import javax.persistence.Column; 4 import javax.persistence.EmbeddedId; 5 import javax.persistence.Entity; 6  7 @Entity 8 public class AirLine { 9     private AirLinePK id;10     private String name;11     12     13     14     public AirLine(){}15     16     public AirLine(AirLinePK id) {17         this.id = id;18     }19     20     public AirLine(String startCity, String endCity, String name) {21         this.id = new AirLinePK(startCity, endCity);22         this.name = name;23     }24     25     @EmbeddedId 26     public AirLinePK getId() {27         return id;28     }29     public void setId(AirLinePK id) {30         this.id = id;31     }32     @Column(length=20)33     public String getName() {34         return name;35     }36     public void setName(String name) {37         this.name = name;38     }39 40 }

 1 @Test 2     public void save() { 3         EntityManagerFactory factory = Persistence.createEntityManagerFactory("YL"); 4         EntityManager em = factory.createEntityManager(); 5         em.getTransaction().begin();//事务开始 6          7         em.persist(new AirLine("PEK", "SHA", "北京飞上海")); 8          9         em.getTransaction().commit();10         em.close();11         factory.close();12     }