当表中一个主键不能唯一标识一条记录的时候，就需要使用联合主键了，下面是使用JPA注解实现联合主键的代码

1 首先需要建立一个复合主键类，用来存放需要生产联合主键的属性，该类需要实现序列化。

package com.ericsson.adp.entity.cons;

import java.io.Serializable;

public class ConsumerGroupMapPK implements Serializable{

private String msisdn;//电话号码

private Long tagGroupId;//(10)标签组id

public String getMsisdn() {

return msisdn;

}

public void setMsisdn(String msisdn) {

this.msisdn = msisdn;

}

public Long getTagGroupId() {

return tagGroupId;

}

public void setTagGroupId(Long tagGroupId) {

this.tagGroupId = tagGroupId;

}

}

然后再写一个类，该类对应数据库中的表，在该类中需要使用@IdClass(ConsumerGroupMapPK.class)引入上面写的复合主键类

同时在需要做成联合主键的属性上面加上@Id标明该属性是主键就好了

package com.ericsson.adp.entity.cons;

import javax.persistence.EmbeddedId;

import javax.persistence.Entity;

import javax.persistence.Id;

import javax.persistence.IdClass;

import javax.persistence.Table;

import org.hibernate.annotations.Cache;

import org.hibernate.annotations.CacheConcurrencyStrategy;

@Entity

@IdClass(ConsumerGroupMapPK.class)

@Table(name="T_CONS_CONSUMER_GROUP_MAP")

@Cache(usage=CacheConcurrencyStrategy.READ_WRITE)

public class ConsumerGroupMap{

@Id

private String msisdn;//电话号码

@Id

private Long tagGroupId;//(10)标签组id

public ConsumerGroupMap() {

super();

// TODO Auto-generated constructor stub

}

public ConsumerGroupMap(String msisdn, Long tagGroupId) {

super();

this.msisdn = msisdn;

this.tagGroupId = tagGroupId;

}

public String getMsisdn() {

return msisdn;

}

public void setMsisdn(String msisdn) {

this.msisdn = msisdn;

}

public Long getTagGroupId() {

return tagGroupId;

}

public void setTagGroupId(Long tagGroupId) {

this.tagGroupId = tagGroupId;

}

}