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：
create table user_project( user_id int(20), project_id int(20), timestamp varchar (50), donate_money double(10,2), primary key (user_id,project_id) );
在网上看了几篇博客，以及在spring boot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
实现
复合主键类
我要评论
package com.hzy.model;
import java.io.serializable;
/**
* created by huangzhenyang on 2017/9/7.
* userproject的复合主键类
*
* @param userid
* @param projectid
* @param timestamp
* 由这三个共同组成复合主键
*/
public class userprojectmultikeysclass implements serializable {
private integer userid;
private integer projectid;
private string timestamp;
//constructor
public userprojectmultikeysclass() {
}
public userprojectmultikeysclass(integer userid, integer projectid, string timestamp) {
this.userid = userid;
this.projectid = projectid;
this.timestamp = timestamp;
}
//setter and getter
public integer getuserid() {
return userid;
}
public void setuserid(integer userid) {
this.userid = userid;
}
public integer getprojectid() {
return projectid;
}
public void setprojectid(integer projectid) {
this.projectid = projectid;
}
public string gettimestamp() {
return timestamp;
}
public void settimestamp(string timestamp) {
this.timestamp = timestamp;
}
// ***重写hashcode与equals方法*** 划重点！
@override
public int hashcode() {
final int prime = 31;
int result = 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());
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 userprojectmultikeysclass other = (userprojectmultikeysclass)obj;
if(userid == null){
if(other.userid != null){
return false;
}
}else if(!userid.equals(other.userid)){
return false;
}
if(projectid == null){
if(other.projectid != null){
return false;
}
}else if(!projectid.equals(other.projectid)){
return false;
}
if(timestamp == null){
if(other.timestamp != null){
return false;
}
}else if(!timestamp.equals(other.timestamp)){
return false;
}
return true;
}
}
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
package com.hzy.model;
import javax.persistence.entity;
import javax.persistence.id;
import javax.persistence.idclass;
import javax.persistence.table;
import java.io.serializable;
/**
* created by huangzhenyang on 2017/9/7.
*
*/
@entity
@table(name = "user_project")
@idclass(userprojectmultikeysclass.class)
public class userproject implements serializable {
private double donatemoney;
private integer userid;
private integer projectid;
private string timestamp;
@id
public integer getuserid(){
return this.userid;
}
@id
public integer getprojectid(){
return this.projectid;
}
@id
public string gettimestamp(){
return this.timestamp;
}
//getter and setter
public double getdonatemoney() {
return donatemoney;
}
public void setdonatemoney(double donatemoney) {
this.donatemoney = donatemoney;
}
public void setuserid(integer userid) {
this.userid = userid;
}
public void setprojectid(integer projectid) {
this.projectid = projectid;
}
public void settimestamp(string timestamp) {
this.timestamp = timestamp;
}
@override
public string tostring() {
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extends jparepository<userproject,userprojectmultikeysclass>时把id的主键类指定为复合主键类userprojectmultikeysclass
public interface userprojectrepository extends jparepository<userproject,userprojectmultikeysclass>{
// 根据用户id,找出用户参与的所有userproject
// test pass
list<userproject> findbyuserid(integer userid);
// 根据项目id,找出参与项目的所有userproject
// test pass
list<userproject> findbyprojectid(integer projectid);
// 根据用户id和项目id 找出所有的userproject
// test pass
list<userproject> findbyuseridandprojectid(integer userid,integer projectid);
}
单元测试的代码
package com.hzy;
import com.hzy.model.userproject;
import com.hzy.model.userprojectmultikeysclass;
import com.hzy.repository.userprojectrepository;
import com.hzy.service.userprojectservice;
import com.hzy.service.userservice;
import org.junit.test;
import org.junit.runner.runwith;
import org.springframework.beans.factory.annotation.autowired;
import org.springframework.boot.test.context.springboottest;
import org.springframework.test.context.junit4.springrunner;
import javax.persistence.entitymanager;
import javax.persistence.persistencecontext;
import javax.transaction.transactional;
import java.util.list;
/**
* created by huangzhenyang on 2017/9/8.
*/
@runwith(springrunner.class)
@springboottest
public class userproejctrepositorytest {
@autowired
@persistencecontext
private entitymanager entitymanager;
@autowired
private userprojectrepository userprojectrepository;
@test
public void testuserprojectrepository(){
userprojectmultikeysclass userprojectmultikeysclass =
new userprojectmultikeysclass(1, 1, "2017-09-08");
userproject userproject = entitymanager.find(userproject.class,userprojectmultikeysclass);
system.out.println(userproject.tostring());
}
@test
public void testfindbyuserid(){
list<userproject> userprojects = userprojectrepository.findbyuserid(1);
for(userproject userproject:userprojects){
system.out.println(userproject.tostring());
}
}
@test
public void testfindbyprojectid(){
list<userproject> userprojects = userprojectrepository.findbyprojectid(1);
for(userproject userproject:userprojects){
system.out.println(userproject.tostring());
}
}
@test
public void testfindbyuseridandprojectid(){
list<userproject> userprojects = userprojectrepository.findbyuseridandprojectid(1,1);
for(userproject userproject:userprojects){
system.out.println(userproject.tostring());
}
}
}
以上就是本文的全部内容，希望对大家的学习有所帮助，也希望大家多多支持移动技术网。
如对本文有疑问， 点击进行留言回复！！
VideoStudio多相机编辑器怎么用? VideoStudio多相机的使用方法
网友评论