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存在於多的一方。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
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
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 接口繼承於 Repository 接口，並新增了簡單的增、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。
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.
*/
@Repository
public 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
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
@Transactional
public 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
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，並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，用於將數據在前台展示。
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";
}
}
前台頁面跳轉
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腳本之家。
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