• Mybatis04关联关系映射

    目录

    一、一对多关联关系

    二、多对多关联关系

    一、一对多关联关系

    1、首先先用逆向生成工具生成t_hibernate_order、t_hibernate_order_item这两张表对应的model与mapper

    1.  <table schema="" tableName="t_hibernate_order" domainObjectName="Order"
    2.            enableCountByExample="false" enableDeleteByExample="false"
    3.            enableSelectByExample="false" enableUpdateByExample="false">
    4.     table>
    5.     <table schema="" tableName="t_hibernate_order_item" domainObjectName="OrderItem"
    6.            enableCountByExample="false" enableDeleteByExample="false"
    7.            enableSelectByExample="false" enableUpdateByExample="false">
    8.     table>

    2、 编写一对多一方面OrderMapper.xml配置文件

    1. "1.0" encoding="UTF-8" ?>
    2. mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN" "http://mybatis.org/dtd/mybatis-3-mapper.dtd" >
    3. <mapper namespace="com.zq.ssm.mapper.OrderMapper" >
    4.   <resultMap id="BaseResultMap" type="com.zq.ssm.model.Order" >
    5.     <constructor >
    6.       <arg column="order_id" jdbcType="VARCHAR" javaType="java.lang.String" />
    7.       <arg column="order_no" jdbcType="VARCHAR" javaType="java.lang.String" />
    8.     constructor>
    9.   resultMap>
    10.  
    11.   <resultMap id="OrdervVoMap" type="com.zq.ssm.model.vo.OrdervVo" >
    12.     <result column="order_id" property="orderId">result>
    13.     <result column="order_no" property="orderNo">result>
    14.     <collection property="orderItems" ofType="com.zking.ssm.model.OrderItem">
    15.       <result column="order_item_id" property="orderItemId">result>
    16.       <result column="product_id" property="productId">result>
    17.       <result column="quantity" property="quantity">result>
    18.       <result column="oid" property="oid">result>
    19.     collection>
    20.   resultMap>
    21.  
    22.   <insert id="insert" parameterType="com.zq.ssm.model.Order" >
    23.     insert into t_hibernate_order (order_id, order_no)
    24.     values (#{orderId,jdbcType=VARCHAR}, #{orderNo,jdbcType=VARCHAR})
    25.   insert>
    26.  
    27.   <select id="queryOrderVoByOrderId" resultMap="OrdervVoMap" parameterType="java.lang.Integer">
    28.    select * from t_hibernate_order o,t_hibernate_order_item oi
    29.     where o.order_id = oi.oid
    30.     and o.order_id = #{orderId}
    31.   select>
    32.   <insert id="insertSelective" parameterType="com.zq.ssm.model.Order" >
    33.     insert into t_hibernate_order
    34.     <trim prefix="(" suffix=")" suffixOverrides="," >
    35.       <if test="orderId != null" >
    36.         order_id,
    37.       if>
    38.       <if test="orderNo != null" >
    39.         order_no,
    40.       if>
    41.     trim>
    42.     <trim prefix="values (" suffix=")" suffixOverrides="," >
    43.       <if test="orderId != null" >
    44.         #{orderId,jdbcType=VARCHAR},
    45.       if>
    46.       <if test="orderNo != null" >
    47.         #{orderNo,jdbcType=VARCHAR},
    48.       if>
    49.     trim>
    50.   insert>
    51. mapper>

    3、创建vo类（包含关联表的信息）

    1. package com.zq.ssm.model.vo;
    2.  
    3. import com.zq.ssm.model.Order;
    4. import com.zq.ssm.model.OrderItem;
    5.  
    6. import java.util.List;
    7.  
    8. /**
    9.  * @author张强
    10.  * @site www.zq.com
    11.  * @create  2022-08-16 12:49
    12.  */
    13. public class OrderVo extends Order {
    14.  
    15.     //通过订单号查询本次订单的详细信息及对应的所有订单项信息
    16.     private List orderItems;
    17.  
    18.     public List getOrderItems() {
    19.         return orderItems;
    20.     }
    21.  
    22.     public void setOrderItems(List orderItems) {
    23.         this.orderItems = orderItems;
    24.     }
    25. }
    1. package com.zq.ssm.model.vo;
    2.  
    3. import com.zq.ssm.model.Order;
    4. import com.zq.ssm.model.OrderItem;
    5.  
    6. /**
    7.  * @author张强
    8.  * @site www.zq.com
    9.  * @create  2022-08-16 12:51
    10.  */
    11. public class OrderItemVo extends OrderItem {
    12.     private Order order;
    13.  
    14.     public Order getOrder() {
    15.         return order;
    16.     }
    17.  
    18.     public void setOrder(Order order) {
    19.         this.order = order;
    20.     }
    21. }

    给实体类添加注解@Data（相当于添加了set/get方法，同时添加了tostring方法）

    1. package com.zq.ssm.model;
    2.  
    3. import lombok.Data;
    4.  
    5. @Data
    6. public class Order {
    7.     private String orderId;
    8.  
    9.     private String orderNo;
    10. }

     OrderItem也是如此

    4、在biz、impl里都添加方法

    1. package com.zq.ssm.biz;
    2.  
    3. import com.zq.ssm.model.Order;
    4. import com.zq.ssm.model.vo.OrderVo;
    5.  
    6. public interface OrderBiz {
    7.     int insert(Order record);
    8.  
    9.     int insertSelective(Order record);
    10.  
    11.     OrderVo queryOrderVoByOrderId( Integer orderId);
    12. }
    1. package com.zq.ssm.biz.impl;
    2.  
    3. import com.zq.ssm.biz.OrderBiz;
    4. import com.zq.ssm.mapper.OrderMapper;
    5. import com.zq.ssm.model.Order;
    6. import com.zq.ssm.model.vo.OrderVo;
    7. import org.springframework.beans.factory.annotation.Autowired;
    8. import org.springframework.stereotype.Service;
    9.  
    10. @Service
    11. public class OrderBizImpl implements OrderBiz {
    12.     @Autowired
    13.     private OrderMapper orderMapper;
    14.     @Override
    15.     public int insert(Order record) {
    16.         return 0;
    17.     }
    18.  
    19.     @Override
    20.     public int insertSelective(Order record) {
    21.         return 0;
    22.     }
    23.  
    24.     @Override
    25.     public OrderVo queryOrderVoByOrderId(Integer orderId) {
    26.         return orderMapper.queryOrderVoByOrderId(orderId);
    27.     }
    28. }

     5、创建测试类

    1. package com.zq.ssm;
    2.  
    3. import com.zq.ssm.biz.OrderBiz;
    4. import com.zq.ssm.model.vo.OrderVo;
    5. import org.junit.Test;
    6. import org.junit.runner.RunWith;
    7. import org.springframework.beans.factory.annotation.Autowired;
    8. import org.springframework.test.context.ContextConfiguration;
    9. import org.springframework.test.context.junit4.SpringJUnit4ClassRunner;
    10.  
    11. /**
    12.  * @author张强
    13.  * @site www.zq.com
    14.  * @create  2022-08-16 13:03
    15.  */
    16. @RunWith(SpringJUnit4ClassRunner.class)
    17. @ContextConfiguration(locations={"classpath:applicationContext-mybatis.xml"})
    18. public class OrderBizImplTest {
    19.     @Autowired
    20.     private OrderBiz orderBiz;
    21.  
    22.  
    23.     @Test
    24.     public void queryOrderVoByOrderId() {
    25.         OrderVo order = orderBiz.queryOrderVoByOrderId(9);
    26.         System.out.println(order);
    27.         order.getOrderItems().forEach(System.out::println);
    28.     }
    29. }

            这样的话便可测试了，接下啦我们实现另外一方的测试

    6、 编写OrderItem.xml方面的文件

    1.  
    2.   <resultMap id="OrderItemVoMap" type="com.zq.ssm.model.vo.OrderItemVo" >
    3.     <result column="order_item_id" property="orderItemId">result>
    4.     <result column="product_id" property="productId">result>
    5.     <result column="quantity" property="quantity">result>
    6.     <result column="oid" property="oid">result>
    7.     <association property="order" javaType="com.zq.ssm.model.Order">
    8.       <result column="order_id" property="orderId">result>
    9.       <result column="order_no" property="orderNo">result>
    10.     association>
    11.   resultMap>
    12.  
    13.   <select id="queryOrderItemVoByOrderItemId" resultMap="OrderItemVoMap" parameterType="java.lang.Integer">
    14.    select * from t_hibernate_order o,t_hibernate_order_item oi
    15.     where o.order_id = oi.oid
    16.     and oi.order_item_id = #{orderItemId}
    17. select>

    接下来的步骤和上面的一样只是这里的配置文件不一样而已，所以我们便可以啦！ 

    二、多对多关联关系

    1、理论：多对多的核心就是两个一对多

    2、逆向生成

    1.  <table schema="" tableName="t_hibernate_book" domainObjectName="Hbook"
    2.                enableCountByExample="false" enableDeleteByExample="false"
    3.                enableSelectByExample="false" enableUpdateByExample="false">
    4.         table>
    5.  
    6.         <table schema="" tableName="t_hibernate_category" domainObjectName="Category"
    7.                enableCountByExample="false" enableDeleteByExample="false"
    8.                enableSelectByExample="false" enableUpdateByExample="false">
    9.         table>
    10.  
    11.         <table schema="" tableName="t_hibernate_book_category" domainObjectName="HbookCategory"
    12.                enableCountByExample="false" enableDeleteByExample="false"
    13.                enableSelectByExample="false" enableUpdateByExample="false">
    14.         table>

    步骤一样我们直接上不一样的地方

    编写XMl配置文件，这个文件我们直接下载中间的标的配置文件中

    1. <resultMap id="HbookVoMap" type="com.zq.ssm.model.vo.HbookVo">
    2.     <result property="bookId" column="book_id">result>
    3.     <result property="bookName" column="book_name">result>
    4.     <collection property="categories" ofType="com.zq.ssm.model.Category">
    5.       <result property="categoryId" column="category_id">result>
    6.       <result property="categoryName" column="category_name">result>
    7.     collection>
    8.   resultMap>
    9.  
    10.   <resultMap id="CategoryVoMap" type="com.zq.ssm.model.vo.CategoryVo">
    11.     <result property="categoryId" column="category_id">result>
    12.     <result property="categoryName" column="category_name">result>
    13.     <collection property="hbooks" ofType="com.zq.ssm.model.Hbook">
    14.       <result property="bookId" column="book_id">result>
    15.       <result property="bookName" column="book_name">result>
    16.     collection>
    17.   resultMap>
    18.  
    19.   <select id="queryByBookId" resultMap="HbookVoMap" parameterType="java.lang.Integer">
    20. select * from t_hibernate_book b,t_hibernate_book_category bc,t_hibernate_category c
    21.      where b.book_id = bc.bid and bc.cid = c.category_id and b.book_id = #{bookId}
    22.  select>
    23.   <select id="queryByCid" resultMap="CategoryVoMap" parameterType="java.lang.Integer">
    24. select * from t_hibernate_book b,t_hibernate_book_category bc,t_hibernate_category c
    25.      where b.book_id = bc.bid and bc.cid = c.category_id and c.category_id=#{cid}
    26.    select>

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  • 原文地址：https://blog.csdn.net/weixin_66110079/article/details/126364081