MyBatis04（关联关系映射）

前言

上一篇文章分享了Mybatis与Spring的集成。本片文章将分享mybatis的关联关系映射。

本次内容将通过案例讲解

一、一对多

一对多：就类似于我们在tb买东西，一次性卖了很多东西，一个订单有很多的订单项。

1、首先我们通过逆向生成工具生成我们将要用到的内容。生成上图两张表。

2、建立对应的对象视图。

OrderVo


package com.zhw.model.vo;
 
import com.zhw.model.Order;
import com.zhw.model.OrderItem;
 
import java.util.List;
 
/**
 * @author louis
 * @create  2022-08-15 18:25
 *
 * 不仅仅包含当前表的信息，还能包含相关联的表的信息。
 */
public class OrderVo extends Order {
//    通过订单号查询本次订单的详细信息以及对应的所有订单项信息
    private List orderItems;
 
    public List getOrderItems() {
        return orderItems;
    }
 
    public void setOrderItems(List orderItems) {
        this.orderItems = orderItems;
    }
}

OrderItemVo


package com.zhw.model.vo;
 
import com.zhw.model.Order;
import com.zhw.model.OrderItem;
import lombok.Data;
 
/**
 * @author louis
 * @create  2022-08-15 18:25
 */
@Data
public class OrderItemVo extends OrderItem {
    private Order order;
 
    public Order getOrder() {
        return order;
    }
 
    public void setOrder(Order order) {
        this.order = order;
    }
}

3、配置对应的xml文件


 <resultMap id="OrderVoMap" type="com.zhw.model.vo.OrderVo">
    <result column="order_id" property="orderId">result>
    <result column="order_no" property="orderNo">result>
    <collection property="orderItems" ofType="com.zhw.model.OrderItem">
      <result column="order_item_id" property="orderItemId">result>
      <result column="product_id" property="productId">result>
      <result column="quantity" property="quantity">result>
      <result column="oid" property="oid">result>
    collection>
  resultMap>


 <resultMap id="OrderItemVoMap" type="com.zhw.model.vo.OrderItemVo">
    <result column="order_item_id" property="orderItemId">result>
    <result column="product_id" property="productId">result>
    <result column="quantity" property="quantity">result>
    <result column="oid" property="oid">result>
    <association property="order" javaType="com.zhw.model.Order">
      <result column="order_id" property="orderId">result>
      <result column="order_no" property="orderNo">result>
    association>
  resultMap>

写注解

OrderBizImpl


package com.zhw.biz.impl;
 
import com.zhw.biz.OrderBiz;
import com.zhw.mapper.OrderMapper;
import com.zhw.model.Order;
import com.zhw.model.vo.OrderVo;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;
 
/**
 * @author louis
 * @create  2022-08-15 19:18
 */
@Service
public class OrderBizImpl implements OrderBiz {
   
    @Autowired
    private OrderMapper orderMapper;
    @Override
    
    @Override
    public OrderVo queryOrderVoByOrderId(Integer orderId) {
        return orderMapper.queryOrderVoByOrderId(orderId);
    }
 
  
}

OrderItemBizImpl


package com.zhw.biz.impl;
 
import com.zhw.biz.OrderItemBiz;
import com.zhw.mapper.OrderItemMapper;
import com.zhw.model.OrderItem;
import com.zhw.model.vo.OrderItemVo;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;
 
/**
 * @author louis
 * @create  2022-08-15 20:06
 */
@Service
public class OrderItemBizImpl implements OrderItemBiz {
    @Autowired
    private OrderItemMapper orderItemMapper;
   
 
    @Override
    public OrderItemVo queryOrderItemVoByOrderItemId(Integer orderItemId) {
        return orderItemMapper.queryOrderItemVoByOrderItemId(orderItemId);
    }
 
    
}

测试类

OrderBizImplTest


package com.zhw.biz.impl;
 
import com.zhw.biz.OrderBiz;
import com.zhw.model.vo.OrderVo;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.test.context.ContextConfiguration;
import org.springframework.test.context.junit4.SpringJUnit4ClassRunner;
 
/**
 * @author louis
 * @create  2022-08-15 19:41
 */
@RunWith(SpringJUnit4ClassRunner.class)
@ContextConfiguration(locations={"classpath:applicationContext-mybatis.xml"})
public class OrderBizImplTest {
    @Autowired
    private OrderBiz orderBiz;
 
    @Test
    public void queryOrderVoByOrderId() {
        OrderVo orderVo = orderBiz.queryOrderVoByOrderId(9);
        System.out.println(orderVo);
    }
}

效果展示

OrderItemBizImplTest


package com.zhw.biz.impl;
 
import com.zhw.biz.OrderItemBiz;
import com.zhw.model.vo.OrderItemVo;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.test.context.ContextConfiguration;
import org.springframework.test.context.junit4.SpringJUnit4ClassRunner;
 
/**
 * @author louis
 * @create  2022-08-15 20:11
 */
@RunWith(SpringJUnit4ClassRunner.class)
@ContextConfiguration(locations={"classpath:applicationContext-mybatis.xml"})
public class OrderItemBizImplTest {
    @Autowired
    private OrderItemBiz orderItemBiz;
 
    @Test
    public void queryOrderItemVoByOrderItemId() {
        OrderItemVo orderItemVo = orderItemBiz.queryOrderItemVoByOrderItemId(43);
        System.out.println(orderItemVo);
        System.out.println(orderItemVo.getOrder());
    }
}

效果展示

二、多对多

多对多相当于两个一对多

多对多：相当于书籍分类，一本书可以属于多个分类，一个分类里面可以有多本书。


 <resultMap id="HbookVoMap" type="com.zhw.model.vo.HbookVo">
    <result property="bookId" column="book_id">result>
    <result property="bookName" column="book_name">result>
    <collection property="categories" ofType="com.zhw.model.Category">
      <result property="categoryId" column="category_id">result>
      <result property="categoryName" column="category_name">result>
    collection>
  resultMap>
 
  <resultMap id="CategoryVoMap" type="com.zhw.model.vo.CategoryVo">
    <result property="categoryId" column="category_id">result>
    <result property="categoryName" column="category_name">result>
    <collection property="hbooks" ofType="com.zhw.model.Hbook">
      <result property="bookId" column="book_id">result>
      <result property="bookName" column="book_name">result>
    collection>
  resultMap>
 
 <select id="queryByBookId" resultMap="HbookVoMap" parameterType="java.lang.Integer">
select * from t_hibernate_book b,t_hibernate_book_category bc,t_hibernate_category c
     where b.book_id = bc.bid and bc.cid = c.category_id and b.book_id = #{bookId}
 select>
 
 
  <select id="queryByCid" resultMap="CategoryVoMap" parameterType="java.lang.Integer">
select * from t_hibernate_book b,t_hibernate_book_category bc,t_hibernate_category c
     where b.book_id = bc.bid and bc.cid = c.category_id and c.category_id=#{cid}
   select>

HbookCategoryBizImpl


package com.zhw.biz.impl;
 
import com.zhw.biz.HbookCategoryBiz;
import com.zhw.mapper.HbookCategoryMapper;
import com.zhw.model.HbookCategory;
import com.zhw.model.vo.CategoryVo;
import com.zhw.model.vo.HbookVo;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;
 
/**
 * @author louis
 * @create  2022-08-15 20:30
 */
@Service
public class HbookCategoryBizImpl implements HbookCategoryBiz {
    @Autowired
    private HbookCategoryMapper hbookCategoryMapper;
 
  
 
    @Override
    public CategoryVo queryByCid(Integer cid) {
        return hbookCategoryMapper.queryByCid(cid);
    }
 
    @Override
    public HbookVo queryByBookId(Integer bookId) {
        return hbookCategoryMapper.queryByBookId(bookId);
    }
}

HbookCategoryBizImplTest


package com.zhw.biz.impl;
 
import com.zhw.biz.HbookCategoryBiz;
import com.zhw.model.vo.CategoryVo;
import com.zhw.model.vo.HbookVo;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.test.context.ContextConfiguration;
import org.springframework.test.context.junit4.SpringJUnit4ClassRunner;
 
/**
 * @author louis
 * @create  2022-08-15 20:33
 */
@RunWith(SpringJUnit4ClassRunner.class)
@ContextConfiguration(locations={"classpath:applicationContext-mybatis.xml"})
public class HbookCategoryBizImplTest {
    @Autowired
    private HbookCategoryBiz hbookCategoryBiz;
 
    @Test
    public void queryByCid() {
        CategoryVo categoryVo = hbookCategoryBiz.queryByCid(8);
        System.out.println(categoryVo);
        categoryVo.getHbooks().forEach(System.out::println);
    }
 
    @Test
    public void queryByBookId() {
        HbookVo hbookVo = hbookCategoryBiz.queryByBookId(8);
        System.out.println(hbookVo);
        hbookVo.getCategories().forEach(System.out::println);
    }
}

效果展示

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原文地址：https://blog.csdn.net/qq_62331938/article/details/126354695