前言
這次大創(chuàng)有個(gè)需求，在數(shù)據(jù)庫(kù)建表時(shí)發(fā)現(xiàn)，user表與project表的關(guān)系表 user_project的主鍵為復(fù)合主鍵：
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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)); |
在網(wǎng)上看了幾篇博客，以及在spring boot干貨群咨詢（感謝夜升額耐心解答）過后總算是做出來(lái)了。這里做個(gè)總結(jié)，方便日后查閱。
正文
這里采用@idclass注解的方式來(lái)實(shí)現(xiàn)復(fù)合主鍵；
思路
- 編寫一個(gè)復(fù)合主鍵類userprojectmultikeysclass;
- 通過@idclass注釋在實(shí)體中標(biāo)注復(fù)合主鍵;
- 可以通過entitymanager獲取數(shù)據(jù)，或者是直接在repository 里寫方法；
實(shí)現(xiàn)
復(fù)合主鍵類
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package com.hzy.model;import java.io.serializable;/** * created by huangzhenyang on 2017/9/7. * userproject的復(fù)合主鍵類 * * @param userid * @param projectid * @param timestamp * 由這三個(gè)共同組成復(fù)合主鍵 */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; } // ***重寫hashcode與equals方法*** 劃重點(diǎn)！ @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：
復(fù)合主鍵類必須滿足：
1. 實(shí)現(xiàn)serializable接口;
2. 有默認(rèn)的public無(wú)參數(shù)的構(gòu)造方法;
3. 重寫equals和hashcode方法。equals方法用于判斷兩個(gè)對(duì)象是否相同，entitymanger通過find方法來(lái)查找entity時(shí)，是根據(jù)equals的返回值來(lái)判斷的。hashcode方法返回當(dāng)前對(duì)象的哈希碼;
實(shí)體類
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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標(biāo)注用于標(biāo)注實(shí)體所使用主鍵規(guī)則的類；
2. 在實(shí)體中同時(shí)標(biāo)注主鍵的屬性，比如這段代碼中的userid,projectid以及timestamp ；
獲取數(shù)據(jù)
方法一： 通過entitymanager獲取，比如方法testuserprojectrepository()
方法二：通過repository獲取；這里記得在extends jparepository<userproject,userprojectmultikeysclass>時(shí)把id的主鍵類指定為復(fù)合主鍵類userprojectmultikeysclass
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public interface userprojectrepository extends jparepository<userproject,userprojectmultikeysclass>{ // 根據(jù)用戶id,找出用戶參與的所有userproject // test pass list<userproject> findbyuserid(integer userid); // 根據(jù)項(xiàng)目id,找出參與項(xiàng)目的所有userproject // test pass list<userproject> findbyprojectid(integer projectid); // 根據(jù)用戶id和項(xiàng)目id 找出所有的userproject // test pass list<userproject> findbyuseridandprojectid(integer userid,integer projectid);} |
單元測(cè)試的代碼
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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)@springboottestpublic 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?jī)?nèi)容，希望對(duì)大家的學(xué)習(xí)有所幫助，也希望大家多多支持服務(wù)器之家。
原文鏈接：https://blog.csdn.net/qq_35056292/article/details/77892012
