springboot data jpa實現 一對多、多對一關聯表查詢
開發環境
- idea 2017.1
- java1.8
- springboot 2.0
- mysql 5.x
功能需求
通過關聯關系查詢商店store中所有的商品shop，商店對商品一對多，商品對商店多對一,外鍵 store_id存在于多的一方。使用數據庫的內連接語句。
表結構
tb_shop
tb_store
實體類，通過注解實現
1.商店類store.java
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package com.gaolei.entity;import javax.persistence.*;import java.util.hashset;import java.util.set;/** * created by gaolei on 2018/6/25. */@entity@table(name = "tb_store")public class store { @id @generatedvalue(strategy = generationtype.identity) private integer id;//商鋪號 private string name;//商鋪姓名 private string address;//商鋪地址 private int tel ;//商鋪聯系 private string info;//商鋪信息 @onetomany(cascade = cascadetype.all,mappedby = "store") private set<shop> shops = new hashset<shop>(); // 省略set()和get()方法；} |
商品類shop.java
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package com.gaolei.entity;import javax.persistence.*;import java.util.hashset;import java.util.set;/** * created by gaolei on 2018/6/25. */@entity@table(name = "tb_shop")public class shop { @id @generatedvalue(strategy = generationtype.identity) private integer id ; //商品id private string name;//商品名 private int price;// 商品價格 private int num;//商品數量 private string info;//商品信息 @manytoone @joincolumn(name = "store_id")//外鍵 private store store; // 省略set()和get()方法；} |
storedao.java
crudrepository 接口繼承于 repository 接口，并新增了簡單的增、刪、查等方法。其中封裝好了很多的方法，這里不再概述，自行百度，這里通過自定義hql語句完成復雜的操作。
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package com.gaolei.dao;import com.gaolei.entity.store;import org.springframework.data.jpa.repository.query;import org.springframework.data.repository.crudrepository;import org.springframework.stereotype.repository;import java.util.list;/** * created by gaolei on 2018/6/25. */@repositorypublic interface storedao extends crudrepository<store,integer> { //此方法通過內連接查詢店鋪id=?中的所有商品 @query("select distinct s from store s inner join s.shops where s.id = ?1") list<store> findbyshoplist(integer id);} |
storeservice.java
通過@autowired注入storedao來實現方法
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package com.gaolei.service;import com.gaolei.dao.storedao;import com.gaolei.entity.shop;import com.gaolei.entity.store;import org.springframework.beans.factory.annotation.autowired;import org.springframework.stereotype.controller;import org.springframework.transaction.annotation.transactional;import java.util.list;/** * created by gaolei on 2018/6/25. */@controller@transactionalpublic class storeservice { @autowired private storedao storedao; /** * 展示商店商品 * */ public list<store> findbyshoplist(integer id){ return storedao.findbyshoplist(id); }} |
storeaction.java
實現具體數據操作操作
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package com.gaolei.action;import com.gaolei.entity.shop;import com.gaolei.entity.store;import com.gaolei.service.shopservice;import com.gaolei.service.storeservice;import org.springframework.beans.factory.annotation.autowired;import org.springframework.stereotype.controller;import org.springframework.ui.model;import org.springframework.web.bind.annotation.requestmapping;import javax.servlet.http.httpservletrequest;import javax.servlet.http.httpservletresponse;import java.util.arraylist;import java.util.list;/** * created by gaolei on 2018/6/26. */@controller@requestmapping("/store")public class storeaction { @autowired private storeservice storeservice; /** * store_shop_menu展示店鋪商品 * */ @requestmapping("showshop") public string showshop(httpservletresponse response ,httpservletrequest request,model model){ string id = request.getparameter("store_id"); //通過hql語句拿到id=?的商鋪，并拿到該店鋪下所有的商品 list<store> list = storeservice.findbyshoplist(integer.valueof(id)); //返回的為一個store集合，store類和shop類為一對多，store下的shops為list<shop>。 list<shop> shoplist = new arraylist<shop>();//循環遍歷拿到每一個shop,添加到一個新的list<shop>中，用于將數據在前臺展示。 for (store store:list){ system.out.println(store.getname()); for (shop shop: store.getshops()) { system.out.println(shop.getname()); shoplist.add(shop); } } model.addattribute("list",shoplist); return "admin/showshop"; }} |
前臺頁面跳轉
查看的店鋪
店鋪商品
省略前端代碼，主要的是@query("****************")中語句使用，配合數據庫的各種連接能實現復雜的操作。
以上就是本文的全部內容，希望對大家的學習有所幫助，也希望大家多多支持服務器之家。
原文鏈接：https://www.jianshu.com/p/1666ac29eb90
