Spring Data Jpa 复合主键的实现

2023-08-24 15:46:04 232

前言

这次大创有个需求，在数据库建表时发现，user表与project表的关系表user_project的主键为复合主键：

CREATETABLEuser_project(
user_idINT(20),
project_idINT(20),
timestampVARCHAR(50),
donate_moneyDOUBLE(10,2),
PRIMARYKEY(user_id,project_id)
);

在网上看了几篇博客，以及在springboot干货群咨询（感谢夜升额耐心解答）过后总算是做出来了。这里做个总结，方便日后查阅。

正文

这里采用@IdClass注解的方式来实现复合主键；

思路

编写一个复合主键类UserProjectMultiKeysClass;
通过@IdClass注释在实体中标注复合主键;
可以通过EntityManager获取数据，或者是直接在Repository里写方法；

实现

复合主键类

packagecom.hzy.Model;

importjava.io.Serializable;

/**
*Createdbyhuangzhenyangon2017/9/7.
*UserProject的复合主键类
*
*@ParamuserId
*@ParamprojectId
*@Paramtimestamp
*由这三个共同组成复合主键
*/
publicclassUserProjectMultiKeysClassimplementsSerializable{
privateIntegeruserId;
privateIntegerprojectId;
privateStringtimestamp;

//Constructor
publicUserProjectMultiKeysClass(){
}

publicUserProjectMultiKeysClass(IntegeruserId,IntegerprojectId,Stringtimestamp){
this.userId=userId;
this.projectId=projectId;
this.timestamp=timestamp;
}

//SetterandGetter
publicIntegergetUserId(){
returnuserId;
}

publicvoidsetUserId(IntegeruserId){
this.userId=userId;
}

publicIntegergetProjectId(){
returnprojectId;
}

publicvoidsetProjectId(IntegerprojectId){
this.projectId=projectId;
}

publicStringgetTimestamp(){
returntimestamp;
}

publicvoidsetTimestamp(Stringtimestamp){
this.timestamp=timestamp;
}

//***重写hashCode与equals方法***划重点！
@Override
publicinthashCode(){
finalintPRIME=31;
intresult=1;
result=PRIME*result+((userId==null)?0:userId.hashCode());
result=PRIME*result+((projectId==null)?0:projectId.hashCode());
result=PRIME*result+((timestamp==null)?0:timestamp.hashCode());
returnresult;
}

@Override
publicbooleanequals(Objectobj){
if(this==obj){
returntrue;
}
if(obj==null){
returnfalse;
}
if(getClass()!=obj.getClass()){
returnfalse;
}

finalUserProjectMultiKeysClassother=(UserProjectMultiKeysClass)obj;
if(userId==null){
if(other.userId!=null){
returnfalse;
}
}elseif(!userId.equals(other.userId)){
returnfalse;
}
if(projectId==null){
if(other.projectId!=null){
returnfalse;
}
}elseif(!projectId.equals(other.projectId)){
returnfalse;
}
if(timestamp==null){
if(other.timestamp!=null){
returnfalse;
}
}elseif(!timestamp.equals(other.timestamp)){
returnfalse;
}

returntrue;
}
}

注意：

复合主键类必须满足：
1.实现Serializable接口;
2.有默认的public无参数的构造方法;
3.重写equals和hashCode方法。equals方法用于判断两个对象是否相同，EntityManger通过find方法来查找Entity时，是根据equals的返回值来判断的。hashCode方法返回当前对象的哈希码;

实体类

packagecom.hzy.Model;

importjavax.persistence.Entity;
importjavax.persistence.Id;
importjavax.persistence.IdClass;
importjavax.persistence.Table;
importjava.io.Serializable;

/**
*Createdbyhuangzhenyangon2017/9/7.
*
*/
@Entity
@Table(name="user_project")
@IdClass(UserProjectMultiKeysClass.class)
publicclassUserProjectimplementsSerializable{
privatedoubledonateMoney;
privateIntegeruserId;
privateIntegerprojectId;
privateStringtimestamp;

@Id
publicIntegergetUserId(){
returnthis.userId;
}

@Id
publicIntegergetProjectId(){
returnthis.projectId;
}

@Id
publicStringgetTimestamp(){
returnthis.timestamp;
}

//getterandsetter
publicdoublegetDonateMoney(){
returndonateMoney;
}

publicvoidsetDonateMoney(doubledonateMoney){
this.donateMoney=donateMoney;
}

publicvoidsetUserId(IntegeruserId){
this.userId=userId;
}

publicvoidsetProjectId(IntegerprojectId){
this.projectId=projectId;
}

publicvoidsetTimestamp(Stringtimestamp){
this.timestamp=timestamp;
}

@Override
publicStringtoString(){
return"UserProject{"+
"donateMoney="+donateMoney+
",userId="+userId+
",projectId="+projectId+
",timestamp='"+timestamp+'\''+
'}';
}
}

注意：
1.@IdClass标注用于标注实体所使用主键规则的类；
2.在实体中同时标注主键的属性，比如这段代码中的userId,projectId以及timestamp；

获取数据

方法一：通过EntityManager获取，比如方法testUserProjectRepository()

方法二：通过Repository获取；这里记得在extendsJpaRepository时把id的主键类指定为复合主键类UserProjectMultiKeysClass

publicinterfaceUserProjectRepositoryextendsJpaRepository{
//根据用户Id,找出用户参与的所有UserProject
//TESTPASS
ListfindByUserId(IntegeruserId);

//根据项目id,找出参与项目的所有UserProject
//TESTPASS
ListfindByProjectId(IntegerprojectId);

//根据用户id和项目id找出所有的UserProject
//TESTPASS
ListfindByUserIdAndProjectId(IntegeruserId,IntegerprojectId);
}

单元测试的代码

packagecom.hzy;

importcom.hzy.Model.UserProject;
importcom.hzy.Model.UserProjectMultiKeysClass;
importcom.hzy.Repository.UserProjectRepository;
importcom.hzy.Service.UserProjectService;
importcom.hzy.Service.UserService;
importorg.junit.Test;
importorg.junit.runner.RunWith;
importorg.springframework.beans.factory.annotation.Autowired;
importorg.springframework.boot.test.context.SpringBootTest;
importorg.springframework.test.context.junit4.SpringRunner;

importjavax.persistence.EntityManager;
importjavax.persistence.PersistenceContext;
importjavax.transaction.Transactional;
importjava.util.List;

/**
*Createdbyhuangzhenyangon2017/9/8.
*/
@RunWith(SpringRunner.class)
@SpringBootTest
publicclassUserProejctRepositoryTest{
@Autowired
@PersistenceContext
privateEntityManagerentityManager;

@Autowired
privateUserProjectRepositoryuserProjectRepository;

@Test
publicvoidtestUserProjectRepository(){
UserProjectMultiKeysClassuserProjectMultiKeysClass=
newUserProjectMultiKeysClass(1,1,"2017-09-08");
UserProjectuserProject=entityManager.find(UserProject.class,userProjectMultiKeysClass);
System.out.println(userProject.toString());
}


@Test
publicvoidtestFindByUserId(){
ListuserProjects=userProjectRepository.findByUserId(1);
for(UserProjectuserProject:userProjects){
System.out.println(userProject.toString());
}
}

@Test
publicvoidtestFindByProjectId(){
ListuserProjects=userProjectRepository.findByProjectId(1);
for(UserProjectuserProject:userProjects){
System.out.println(userProject.toString());
}
}

@Test
publicvoidtestFindByUserIdAndProjectId(){
ListuserProjects=userProjectRepository.findByUserIdAndProjectId(1,1);
for(UserProjectuserProject:userProjects){
System.out.println(userProject.toString());
}
}
}

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Spring Data Jpa 复合主键的实现

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