关联关系映射《一对多&&多对多的业务处理》

目录

一、一对多关联关系

1.1 逆向生成代码的配置文件

1.2 编写配置文件：OrderMapper.xml

1.3 我们需要建立一个Vo类，

二、多对多关联关系

 2.1 逆向生成代码

一、一对多关联关系

1.1 逆向生成代码的配置文件

需求案例1：通过订单号查询本次订单的详情信息及对应的所有订单

逆向生成代码的配置文件：

generatorConfig.xml

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE generatorConfiguration PUBLIC "-//mybatis.org//DTD MyBatis Generator Configuration 1.0//EN"
        "http://mybatis.org/dtd/mybatis-generator-config_1_0.dtd" >
<generatorConfiguration>
    <!-- 引入配置文件 -->
    <properties resource="jdbc.properties"/>

    <!--指定数据库jdbc驱动jar包的位置-->
    <classPathEntry location="E:\\AnZhuangBao\\Maven\\mvn_repository\\mysql\\mysql-connector-java\\5.1.44\\mysql-connector-java-5.1.44.jar"/>

    <!-- 一个数据库一个context -->
    <context id="infoGuardian">
        <!-- 注释 -->
        <commentGenerator>
            <property name="suppressAllComments" value="true"/><!-- 是否取消注释 -->
            <property name="suppressDate" value="true"/> <!-- 是否生成注释代时间戳 -->
        </commentGenerator>

        <!-- jdbc连接 -->
        <jdbcConnection driverClass="${jdbc.driver}"
                        connectionURL="${jdbc.url}" userId="${jdbc.username}" password="${jdbc.password}"/>

        <!-- 类型转换 -->
        <javaTypeResolver>
            <!-- 是否使用bigDecimal， false可自动转化以下类型（Long, Integer, Short, etc.） -->
            <property name="forceBigDecimals" value="false"/>
        </javaTypeResolver>

        <!-- 01 指定javaBean生成的位置 -->
        <!-- targetPackage：指定生成的model生成所在的包名 -->
        <!-- targetProject：指定在该项目下所在的路径  -->
        <javaModelGenerator targetPackage="com.leaf.ssm.model"
                            targetProject="src/main/java">
            <!-- 是否允许子包，即targetPackage.schemaName.tableName -->
            <property name="enableSubPackages" value="false"/>
            <!-- 是否对model添加构造函数 -->
            <property name="constructorBased" value="true"/>
            <!-- 是否针对string类型的字段在set的时候进行trim调用 -->
            <property name="trimStrings" value="false"/>
            <!-- 建立的Model对象是否 不可改变  即生成的Model对象不会有 setter方法，只有构造方法 -->
            <property name="immutable" value="false"/>
        </javaModelGenerator>

        <!-- 02 指定sql映射文件生成的位置 -->
        <sqlMapGenerator targetPackage="com.leaf.ssm.mapper"
                         targetProject="src/main/java">
            <!-- 是否允许子包，即targetPackage.schemaName.tableName -->
            <property name="enableSubPackages" value="false"/>
        </sqlMapGenerator>

        <!-- 03 生成XxxMapper接口 -->
        <!-- type="ANNOTATEDMAPPER",生成Java Model 和基于注解的Mapper对象 -->
        <!-- type="MIXEDMAPPER",生成基于注解的Java Model 和相应的Mapper对象 -->
        <!-- type="XMLMAPPER",生成SQLMap XML文件和独立的Mapper接口 -->
        <javaClientGenerator targetPackage="com.leaf.ssm.mapper"
                             targetProject="src/main/java" type="XMLMAPPER">
            <!-- 是否在当前路径下新加一层schema,false路径com.oop.eksp.user.model， true:com.oop.eksp.user.model.[schemaName] -->
            <property name="enableSubPackages" value="false"/>
        </javaClientGenerator>

        <!-- 配置表信息 -->
        <!-- schema即为数据库名 -->
        <!-- tableName为对应的数据库表 -->
        <!-- domainObjectName是要生成的实体类 -->
        <!-- enable*ByExample是否生成 example类 -->
        <!--<table schema="" tableName="t_book" domainObjectName="Book"-->
        <!--enableCountByExample="false" enableDeleteByExample="false"-->
        <!--enableSelectByExample="false" enableUpdateByExample="false">-->
        <!--&lt;!&ndash; 忽略列，不生成bean 字段 &ndash;&gt;-->
        <!--&lt;!&ndash; <ignoreColumn column="FRED" /> &ndash;&gt;-->
        <!--&lt;!&ndash; 指定列的java数据类型 &ndash;&gt;-->
        <!--&lt;!&ndash; <columnOverride column="LONG_VARCHAR_FIELD" jdbcType="VARCHAR" /> &ndash;&gt;-->
        <!--</table>-->

        <table schema="" tableName="t_hibernate_order" domainObjectName="Order"
               enableCountByExample="false" enableDeleteByExample="false"
               enableSelectByExample="false" enableUpdateByExample="false">
        </table>

        <table schema="" tableName="t_hibernate_order_item" domainObjectName="OrderItem"
               enableCountByExample="false" enableDeleteByExample="false"
               enableSelectByExample="false" enableUpdateByExample="false">
        </table>

    </context>
</generatorConfiguration>

逆向生成代码后我们就可以开始

1.2 编写配置文件：OrderMapper.xml

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN" "http://mybatis.org/dtd/mybatis-3-mapper.dtd" >
<mapper namespace="com.leaf.ssm.mapper.OrderMapper" >
  <resultMap id="BaseResultMap" type="com.leaf.ssm.model.Order" >
    <constructor >
      <idArg column="order_id" jdbcType="INTEGER" javaType="java.lang.Integer" />
      <arg column="order_no" jdbcType="VARCHAR" javaType="java.lang.String" />
    </constructor>
  </resultMap>
  <sql id="Base_Column_List" >
    order_id, order_no
  </sql>

  <resultMap id="OrderVoMap" type="com.leaf.ssm.model.vo.OrderVo" >
    <result column="order_id" property="orderId"></result>
    <result column="order_no" property="orderNo"></result>
    <collection property="orderItems" ofType="com.leaf.ssm.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>

  <select id="queryOrderVoByOrderId" resultMap="OrderVoMap" parameterType="java.lang.Integer" >
    select * from t_hibernate_order o,t_hibernate_order_item oi
    where o.order_id = oi.oid and o.order_id = #{orderId}
  </select>

  <select id="selectByPrimaryKey" resultMap="BaseResultMap" parameterType="java.lang.Integer" >
    select 
    <include refid="Base_Column_List" />
    from t_hibernate_order
    where order_id = #{orderId,jdbcType=INTEGER}
  </select>
  <delete id="deleteByPrimaryKey" parameterType="java.lang.Integer" >
    delete from t_hibernate_order
    where order_id = #{orderId,jdbcType=INTEGER}
  </delete>
  <insert id="insert" parameterType="com.leaf.ssm.model.Order" >
    insert into t_hibernate_order (order_id, order_no)
    values (#{orderId,jdbcType=INTEGER}, #{orderNo,jdbcType=VARCHAR})
  </insert>
  <insert id="insertSelective" parameterType="com.leaf.ssm.model.Order" >
    insert into t_hibernate_order
    <trim prefix="(" suffix=")" suffixOverrides="," >
      <if test="orderId != null" >
        order_id,
      </if>
      <if test="orderNo != null" >
        order_no,
      </if>
    </trim>
    <trim prefix="values (" suffix=")" suffixOverrides="," >
      <if test="orderId != null" >
        #{orderId,jdbcType=INTEGER},
      </if>
      <if test="orderNo != null" >
        #{orderNo,jdbcType=VARCHAR},
      </if>
    </trim>
  </insert>
  <update id="updateByPrimaryKeySelective" parameterType="com.leaf.ssm.model.Order" >
    update t_hibernate_order
    <set >
      <if test="orderNo != null" >
        order_no = #{orderNo,jdbcType=VARCHAR},
      </if>
    </set>
    where order_id = #{orderId,jdbcType=INTEGER}
  </update>
  <update id="updateByPrimaryKey" parameterType="com.leaf.ssm.model.Order" >
    update t_hibernate_order
    set order_no = #{orderNo,jdbcType=VARCHAR}
    where order_id = #{orderId,jdbcType=INTEGER}
  </update>
</mapper>

1.3 我们需要建立一个Vo类，

里面不仅仅包含当前表的信息、还能包含相关联的表的信息。

BookVo：

package com.leaf.ssm.model.vo;

import com.leaf.ssm.model.Order;
import com.leaf.ssm.model.OrderItem;

import java.util.List;

/**
 * @author Leaf
 * @site 2977819715
 * @company 玉渊工作室
 * @create  2022-08-16 0:15
 *
 * Vo类不仅仅包含当前表的信息、还能包含相关联的表的信息
 *
 * 当前订单会有一个或者多个订单项，多个订单先必须要集合进行接受
 */
public class OrderVo extends Order {
    //需求1：通过订单号查询本次订单的详情信息及对应的所有订单
    private List<OrderItem> orderItems;

    public List<OrderItem> getOrderItems() {
        return orderItems;
    }

    public void setOrderItems(List<OrderItem> orderItems) {
        this.orderItems = orderItems;
    }
}

BookItemVo： 

package com.leaf.ssm.model.vo;

import com.leaf.ssm.model.Order;
import com.leaf.ssm.model.OrderItem;
import lombok.Data;

/**
 * @author Leaf
 * @site 2977819715
 * @company 玉渊工作室
 * @create  2022-08-16 0:25
 *
 * 某一个订单项一定属于某个订单的
 */
@Data
public class OrderItemVo extends OrderItem {

    private Order order;

    public Order getOrder() {
        return order;
    }

    public void setOrder(Order order) {
        this.order = order;
    }
}

添加@Data注释：省略了get、set、toString、构造方法。  

再然后分别在OrderMapper.java 和 OrderBiz 里面添加查询的方法：

    OrderVo queryOrderVoByOrderId(@Param("orderId") Integer orderId);

 创建实现类：OrderBizImpl

package com.leaf.ssm.biz.impl;

import com.leaf.ssm.biz.OrderBiz;
import com.leaf.ssm.mapper.OrderMapper;
import com.leaf.ssm.model.Order;
import com.leaf.ssm.model.vo.OrderVo;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;

/**
 * @author Leaf
 * @site 2977819715
 * @company 玉渊工作室
 * @create  2022-08-16 0:52
 */
@Service
public class OrderBizImpl implements OrderBiz {

    @Autowired
    private OrderMapper orderMapper;

    @Override
    public int deleteByPrimaryKey(Integer orderId) {
        return 0;
    }

    @Override
    public int insert(Order record) {
        return 0;
    }

    @Override
    public int insertSelective(Order record) {
        return 0;
    }

    @Override
    public Order selectByPrimaryKey(Integer orderId) {
        return null;
    }

    @Override
    public OrderVo queryOrderVoByOrderId(Integer orderId) {
        return orderMapper.queryOrderVoByOrderId(orderId);
    }

    @Override
    public int updateByPrimaryKeySelective(Order record) {
        return 0;
    }

    @Override
    public int updateByPrimaryKey(Order record) {
        return 0;
    }
}

测试类：OrderBizImplTest

package com.leaf.ssm.biz.impl;

import com.leaf.ssm.biz.OrderBiz;
import com.leaf.ssm.model.Order;
import com.leaf.ssm.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;

import static org.junit.Assert.*;

/**
 * @author Leaf
 * @site 2977819715
 * @company 玉渊工作室
 * @create  2022-08-16 0:54
 */
@RunWith(SpringJUnit4ClassRunner.class)
@ContextConfiguration(locations={"classpath:applicationContext-mybatis.xml"})
public class OrderBizImplTest {

    @Autowired
    private OrderBiz orderBiz;

    //需求1：通过订单号查询本次订单的详情信息及对应的所有订单
    //select * from t_hibernate_order o,t_hibernate_order_item oi
    //where o.order_id = oi.oid and o.order_id = 9
    @Test
    public void queryOrderVoByOrderId() {
        OrderVo orderVo = orderBiz.queryOrderVoByOrderId(9);
        System.out.println(orderVo);
        //打印订单项
        System.out.println(orderVo.getOrderItems());
    }

}

 一对多的一运行结果：

 接着我们来配置实现一对多的多，

需求案例2：通过订单项ID查询出订单项详细信息及所有订单

步骤是一样的：

配置文件：OrderItemMapper.xml

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN" "http://mybatis.org/dtd/mybatis-3-mapper.dtd" >
<mapper namespace="com.leaf.ssm.mapper.OrderItemMapper" >
  <resultMap id="BaseResultMap" type="com.leaf.ssm.model.OrderItem" >
    <constructor >
      <idArg column="order_item_id" jdbcType="INTEGER" javaType="java.lang.Integer" />
      <arg column="product_id" jdbcType="INTEGER" javaType="java.lang.Integer" />
      <arg column="quantity" jdbcType="INTEGER" javaType="java.lang.Integer" />
      <arg column="oid" jdbcType="INTEGER" javaType="java.lang.Integer" />
    </constructor>
  </resultMap>
  <sql id="Base_Column_List" >
    order_item_id, product_id, quantity, oid
  </sql>

  <resultMap id="OrderItemVoMap" type="com.leaf.ssm.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.leaf.ssm.model.Order">
      <result column="order_id" property="orderId"></result>
      <result column="order_no" property="orderNo"></result>
    </association>

  </resultMap>

  <select id="queryOrderItemVoByOrderItemId" resultMap="OrderItemVoMap" parameterType="java.lang.Integer" >
    select * from t_hibernate_order o,t_hibernate_order_item oi
    where o.order_id = oi.oid and oi.order_item_id = #{orderItemId}
  </select>

  <select id="selectByPrimaryKey" resultMap="BaseResultMap" parameterType="java.lang.Integer" >
    select 
    <include refid="Base_Column_List" />
    from t_hibernate_order_item
    where order_item_id = #{orderItemId,jdbcType=INTEGER}
  </select>
  <delete id="deleteByPrimaryKey" parameterType="java.lang.Integer" >
    delete from t_hibernate_order_item
    where order_item_id = #{orderItemId,jdbcType=INTEGER}
  </delete>
  <insert id="insert" parameterType="com.leaf.ssm.model.OrderItem" >
    insert into t_hibernate_order_item (order_item_id, product_id, quantity, 
      oid)
    values (#{orderItemId,jdbcType=INTEGER}, #{productId,jdbcType=INTEGER}, #{quantity,jdbcType=INTEGER}, 
      #{oid,jdbcType=INTEGER})
  </insert>
  <insert id="insertSelective" parameterType="com.leaf.ssm.model.OrderItem" >
    insert into t_hibernate_order_item
    <trim prefix="(" suffix=")" suffixOverrides="," >
      <if test="orderItemId != null" >
        order_item_id,
      </if>
      <if test="productId != null" >
        product_id,
      </if>
      <if test="quantity != null" >
        quantity,
      </if>
      <if test="oid != null" >
        oid,
      </if>
    </trim>
    <trim prefix="values (" suffix=")" suffixOverrides="," >
      <if test="orderItemId != null" >
        #{orderItemId,jdbcType=INTEGER},
      </if>
      <if test="productId != null" >
        #{productId,jdbcType=INTEGER},
      </if>
      <if test="quantity != null" >
        #{quantity,jdbcType=INTEGER},
      </if>
      <if test="oid != null" >
        #{oid,jdbcType=INTEGER},
      </if>
    </trim>
  </insert>
  <update id="updateByPrimaryKeySelective" parameterType="com.leaf.ssm.model.OrderItem" >
    update t_hibernate_order_item
    <set >
      <if test="productId != null" >
        product_id = #{productId,jdbcType=INTEGER},
      </if>
      <if test="quantity != null" >
        quantity = #{quantity,jdbcType=INTEGER},
      </if>
      <if test="oid != null" >
        oid = #{oid,jdbcType=INTEGER},
      </if>
    </set>
    where order_item_id = #{orderItemId,jdbcType=INTEGER}
  </update>
  <update id="updateByPrimaryKey" parameterType="com.leaf.ssm.model.OrderItem" >
    update t_hibernate_order_item
    set product_id = #{productId,jdbcType=INTEGER},
      quantity = #{quantity,jdbcType=INTEGER},
      oid = #{oid,jdbcType=INTEGER}
    where order_item_id = #{orderItemId,jdbcType=INTEGER}
  </update>
</mapper>

订单项的Vo：OrderItemVo

package com.leaf.ssm.model.vo;

import com.leaf.ssm.model.Order;
import com.leaf.ssm.model.OrderItem;
import lombok.Data;

/**
 * @author Leaf
 * @site 2977819715
 * @company 玉渊工作室
 * @create  2022-08-16 0:25
 *
 * 某一个订单项一定属于某个订单的
 */
@Data
public class OrderItemVo extends OrderItem {

    private Order order;

    public Order getOrder() {
        return order;
    }

    public void setOrder(Order order) {
        
        this.order = order;
    }
}

 分别往 OrderItemMapper.java 和 OrderItemBiz 接口里面添加测试的方法：

OrderItemVo queryOrderItemVoByOrderItemId(@Param("orderItemId") Integer orderItemId);

建立实现类：OrderItemBizImpl

package com.leaf.ssm.biz.impl;

import com.leaf.ssm.biz.OrderItemBiz;
import com.leaf.ssm.mapper.OrderItemMapper;
import com.leaf.ssm.model.OrderItem;
import com.leaf.ssm.model.vo.OrderItemVo;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;

/**
 * @author Leaf
 * @site 2977819715
 * @company 玉渊工作室
 * @create  2022-08-16 1:28
 */
@Service
public class OrderItemBizImpl implements OrderItemBiz {

    @Autowired
    private OrderItemMapper orderItemMapper;

    @Override
    public int deleteByPrimaryKey(Integer orderItemId) {
        return 0;
    }

    @Override
    public int insert(OrderItem record) {
        return 0;
    }

    @Override
    public int insertSelective(OrderItem record) {
        return 0;
    }

    @Override
    public OrderItem selectByPrimaryKey(Integer orderItemId) {
        return null;
    }

    @Override
    public OrderItemVo queryOrderItemVoByOrderItemId(Integer orderItemId) {
        return orderItemMapper.queryOrderItemVoByOrderItemId(orderItemId);
    }

    @Override
    public int updateByPrimaryKeySelective(OrderItem record) {
        return 0;
    }

    @Override
    public int updateByPrimaryKey(OrderItem record) {
        return 0;
    }
}

 建立测试类：OrderItemBizImplTest

package com.leaf.ssm.biz.impl;

import com.leaf.ssm.biz.OrderItemBiz;
import com.leaf.ssm.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;

import static org.junit.Assert.*;

/**
 * @author Leaf
 * @site 2977819715
 * @company 玉渊工作室
 * @create  2022-08-16 1:29
 */
@RunWith(SpringJUnit4ClassRunner.class)
@ContextConfiguration(locations={"classpath:applicationContext-mybatis.xml"})
public class OrderItemBizImplTest {

    @Autowired
    private OrderItemBiz orderItemBiz;

    //需求2：通过订单项ID查询出订单项详细信息及所有订单
    //select * from t_hibernate_order o,t_hibernate_order_item oi
    //where o.order_id = oi.oid and oi.order_item_id = 43
    @Test
    public void queryOrderItemVoByOrderItemId() {
        OrderItemVo orderItemVo = orderItemBiz.queryOrderItemVoByOrderItemId(43);
        System.out.println(orderItemVo);
        //打印订单
        System.out.println(orderItemVo.getOrder());
    }
}

运行结果：

注：一定要注意上面代码中的注解，都是有用的，不能少也不能错。 

一对多的核心理论：

Collection：一对多的一方，对应关联属性用ofType

Association：一对多的多方，对应关联属性用javaType

二、多对多关联关系

理论核心：多对多就是两个一对多

需求案例1：根据书籍ID，查询书籍信息及所属所有类别信息；

 2.1 逆向生成代码

配置要生成的实体类：generatorConfig.xml

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE generatorConfiguration PUBLIC "-//mybatis.org//DTD MyBatis Generator Configuration 1.0//EN"
        "http://mybatis.org/dtd/mybatis-generator-config_1_0.dtd" >
<generatorConfiguration>
    <!-- 引入配置文件 -->
    <properties resource="jdbc.properties"/>

    <!--指定数据库jdbc驱动jar包的位置-->
    <classPathEntry location="E:\\AnZhuangBao\\Maven\\mvn_repository\\mysql\\mysql-connector-java\\5.1.44\\mysql-connector-java-5.1.44.jar"/>

    <!-- 一个数据库一个context -->
    <context id="infoGuardian">
        <!-- 注释 -->
        <commentGenerator>
            <property name="suppressAllComments" value="true"/><!-- 是否取消注释 -->
            <property name="suppressDate" value="true"/> <!-- 是否生成注释代时间戳 -->
        </commentGenerator>

        <!-- jdbc连接 -->
        <jdbcConnection driverClass="${jdbc.driver}"
                        connectionURL="${jdbc.url}" userId="${jdbc.username}" password="${jdbc.password}"/>

        <!-- 类型转换 -->
        <javaTypeResolver>
            <!-- 是否使用bigDecimal， false可自动转化以下类型（Long, Integer, Short, etc.） -->
            <property name="forceBigDecimals" value="false"/>
        </javaTypeResolver>

        <!-- 01 指定javaBean生成的位置 -->
        <!-- targetPackage：指定生成的model生成所在的包名 -->
        <!-- targetProject：指定在该项目下所在的路径  -->
        <javaModelGenerator targetPackage="com.leaf.ssm.model"
                            targetProject="src/main/java">
            <!-- 是否允许子包，即targetPackage.schemaName.tableName -->
            <property name="enableSubPackages" value="false"/>
            <!-- 是否对model添加构造函数 -->
            <property name="constructorBased" value="true"/>
            <!-- 是否针对string类型的字段在set的时候进行trim调用 -->
            <property name="trimStrings" value="false"/>
            <!-- 建立的Model对象是否 不可改变  即生成的Model对象不会有 setter方法，只有构造方法 -->
            <property name="immutable" value="false"/>
        </javaModelGenerator>

        <!-- 02 指定sql映射文件生成的位置 -->
        <sqlMapGenerator targetPackage="com.leaf.ssm.mapper"
                         targetProject="src/main/java">
            <!-- 是否允许子包，即targetPackage.schemaName.tableName -->
            <property name="enableSubPackages" value="false"/>
        </sqlMapGenerator>

        <!-- 03 生成XxxMapper接口 -->
        <!-- type="ANNOTATEDMAPPER",生成Java Model 和基于注解的Mapper对象 -->
        <!-- type="MIXEDMAPPER",生成基于注解的Java Model 和相应的Mapper对象 -->
        <!-- type="XMLMAPPER",生成SQLMap XML文件和独立的Mapper接口 -->
        <javaClientGenerator targetPackage="com.leaf.ssm.mapper"
                             targetProject="src/main/java" type="XMLMAPPER">
            <!-- 是否在当前路径下新加一层schema,false路径com.oop.eksp.user.model， true:com.oop.eksp.user.model.[schemaName] -->
            <property name="enableSubPackages" value="false"/>
        </javaClientGenerator>

        <!-- 配置表信息 -->
        <!-- schema即为数据库名 -->
        <!-- tableName为对应的数据库表 -->
        <!-- domainObjectName是要生成的实体类 -->
        <!-- enable*ByExample是否生成 example类 -->
        <!--<table schema="" tableName="t_book" domainObjectName="Book"-->
        <!--enableCountByExample="false" enableDeleteByExample="false"-->
        <!--enableSelectByExample="false" enableUpdateByExample="false">-->
        <!--&lt;!&ndash; 忽略列，不生成bean 字段 &ndash;&gt;-->
        <!--&lt;!&ndash; <ignoreColumn column="FRED" /> &ndash;&gt;-->
        <!--&lt;!&ndash; 指定列的java数据类型 &ndash;&gt;-->
        <!--&lt;!&ndash; <columnOverride column="LONG_VARCHAR_FIELD" jdbcType="VARCHAR" /> &ndash;&gt;-->
        <!--</table>-->

        <table schema="" tableName="t_hibernate_book" domainObjectName="Hbook"
               enableCountByExample="false" enableDeleteByExample="false"
               enableSelectByExample="false" enableUpdateByExample="false">
        </table>

        <table schema="" tableName="t_hibernate_category" domainObjectName="Category"
               enableCountByExample="false" enableDeleteByExample="false"
               enableSelectByExample="false" enableUpdateByExample="false">
        </table>

        <table schema="" tableName="t_hibernate_book_category" domainObjectName="HbookCategory"
               enableCountByExample="false" enableDeleteByExample="false"
               enableSelectByExample="false" enableUpdateByExample="false">
        </table>

    </context>
</generatorConfiguration>

逆向生成代码成功： 

创建Vo类：CategoryVo

package com.leaf.ssm.model.vo;

import com.leaf.ssm.model.Category;
import com.leaf.ssm.model.Hbook;
import lombok.Data;
import lombok.ToString;

import java.util.List;

/**
 * @author Leaf
 * @site 2977819715
 * @company 玉渊工作室
 * @create  2022-08-16 7:56
 */
@Data
public class CategoryVo extends Category {
    private List<Hbook> hbooks;

    public List<Hbook> getHbooks() {
        return hbooks;
    }

    public void setHbooks(List<Hbook> hbooks) {
        this.hbooks = hbooks;
    }
}

 HbookVo

package com.leaf.ssm.model.vo;

import com.leaf.ssm.model.Category;
import com.leaf.ssm.model.Hbook;
import lombok.Data;

import java.util.List;

/**
 * @author Leaf
 * @site 2977819715
 * @company 玉渊工作室
 * @create  2022-08-16 7:55
 */
@Data
public class HbookVo extends Hbook {
    private List<Category> categories;

    public List<Category> getCategories() {
        return categories;
    }

    public void setCategories(List<Category> categories) {
        this.categories = categories;
    }
}

配置我们公共的一个SQL的XML文件：HbookCategoryMapper.xml

这样就不用再去另两个类配置了；

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN" "http://mybatis.org/dtd/mybatis-3-mapper.dtd" >
<mapper namespace="com.leaf.ssm.mapper.HbookCategoryMapper" >
  <resultMap id="BaseResultMap" type="com.leaf.ssm.model.HbookCategory" >
    <constructor >
      <idArg column="bcid" jdbcType="INTEGER" javaType="java.lang.Integer" />
      <arg column="bid" jdbcType="INTEGER" javaType="java.lang.Integer" />
      <arg column="cid" jdbcType="INTEGER" javaType="java.lang.Integer" />
    </constructor>
  </resultMap>
  <sql id="Base_Column_List" >
    bcid, bid, cid
  </sql>

  <resultMap id="HbookVoMap" type="com.leaf.ssm.model.vo.HbookVo">
    <result property="bookId" column="book_id"></result>
    <result property="bookName" column="book_name"></result>
    <collection property="categories" ofType="com.leaf.ssm.model.Category">
      <result property="categoryId" column="category_id"></result>
      <result property="categoryName" column="category_name"></result>
    </collection>
  </resultMap>

  <resultMap id="CategoryVoMap" type="com.leaf.ssm.model.vo.CategoryVo">
    <result property="categoryId" column="category_id"></result>
    <result property="categoryName" column="category_name"></result>
    <collection property="hbooks" ofType="com.leaf.ssm.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>

  <select id="selectByPrimaryKey" resultMap="BaseResultMap" parameterType="java.lang.Integer" >
    select 
    <include refid="Base_Column_List" />
    from t_hibernate_book_category
    where bcid = #{bcid,jdbcType=INTEGER}
  </select>
  <delete id="deleteByPrimaryKey" parameterType="java.lang.Integer" >
    delete from t_hibernate_book_category
    where bcid = #{bcid,jdbcType=INTEGER}
  </delete>
  <insert id="insert" parameterType="com.leaf.ssm.model.HbookCategory" >
    insert into t_hibernate_book_category (bcid, bid, cid
      )
    values (#{bcid,jdbcType=INTEGER}, #{bid,jdbcType=INTEGER}, #{cid,jdbcType=INTEGER}
      )
  </insert>
  <insert id="insertSelective" parameterType="com.leaf.ssm.model.HbookCategory" >
    insert into t_hibernate_book_category
    <trim prefix="(" suffix=")" suffixOverrides="," >
      <if test="bcid != null" >
        bcid,
      </if>
      <if test="bid != null" >
        bid,
      </if>
      <if test="cid != null" >
        cid,
      </if>
    </trim>
    <trim prefix="values (" suffix=")" suffixOverrides="," >
      <if test="bcid != null" >
        #{bcid,jdbcType=INTEGER},
      </if>
      <if test="bid != null" >
        #{bid,jdbcType=INTEGER},
      </if>
      <if test="cid != null" >
        #{cid,jdbcType=INTEGER},
      </if>
    </trim>
  </insert>
  <update id="updateByPrimaryKeySelective" parameterType="com.leaf.ssm.model.HbookCategory" >
    update t_hibernate_book_category
    <set >
      <if test="bid != null" >
        bid = #{bid,jdbcType=INTEGER},
      </if>
      <if test="cid != null" >
        cid = #{cid,jdbcType=INTEGER},
      </if>
    </set>
    where bcid = #{bcid,jdbcType=INTEGER}
  </update>
  <update id="updateByPrimaryKey" parameterType="com.leaf.ssm.model.HbookCategory" >
    update t_hibernate_book_category
    set bid = #{bid,jdbcType=INTEGER},
      cid = #{cid,jdbcType=INTEGER}
    where bcid = #{bcid,jdbcType=INTEGER}
  </update>
</mapper>

* 需求2：根据类别ID，查询类别信息及所包含书籍信息

然后还是一样的，我们依次在 HbookCategoryMapper 和 HbookCategoryBiz 添加测试的方法：

HbookVo queryByBookId(@Param("bookId") Integer bookId);

CategoryVo queryByCid(@Param("cid") Integer cid);

创建实现类：HbookCategoryBizImpl 

package com.leaf.ssm.biz.impl;

import com.leaf.ssm.biz.HbookCategoryBiz;
import com.leaf.ssm.mapper.HbookCategoryMapper;
import com.leaf.ssm.model.HbookCategory;
import com.leaf.ssm.model.vo.CategoryVo;
import com.leaf.ssm.model.vo.HbookVo;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;

/**
 * @author Leaf
 * @site 2977819715
 * @company 玉渊工作室
 * @create  2022-08-16 8:03
 */
@Service
public class HbookCategoryBizImpl implements HbookCategoryBiz {

    @Autowired
    private HbookCategoryMapper hbookCategoryMapper;

    @Override
    public int deleteByPrimaryKey(Integer bcid) {
        return 0;
    }

    @Override
    public int insert(HbookCategory record) {
        return 0;
    }

    @Override
    public int insertSelective(HbookCategory record) {
        return 0;
    }

    @Override
    public HbookCategory selectByPrimaryKey(Integer bcid) {
        return null;
    }

    @Override
    public int updateByPrimaryKeySelective(HbookCategory record) {
        return 0;
    }

    @Override
    public int updateByPrimaryKey(HbookCategory record) {
        return 0;
    }

    @Override
    public HbookVo queryByBookId(Integer bookId) {
        return hbookCategoryMapper.queryByBookId(bookId);
    }

    @Override
    public CategoryVo queryByCid(Integer cid) {
        return hbookCategoryMapper.queryByCid(cid);
    }
}

然后再创建测试类进行测试：HbookCategoryBizImplTest

package com.leaf.ssm.biz.impl;

import com.leaf.ssm.biz.HbookCategoryBiz;
import com.leaf.ssm.model.vo.CategoryVo;
import com.leaf.ssm.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;

import static org.junit.Assert.*;

/**
 * @author Leaf
 * @site 2977819715
 * @company 玉渊工作室
 * @create  2022-08-16 8:05
 */
@RunWith(SpringJUnit4ClassRunner.class)
@ContextConfiguration(locations={"classpath:applicationContext-mybatis.xml"})
public class HbookCategoryBizImplTest {

    @Autowired
    private HbookCategoryBiz hbookCategoryBiz;

    @Test
    public void queryByBookId() {
        HbookVo hbookVo = hbookCategoryBiz.queryByBookId(8);
        System.out.println(hbookVo);
    }

    @Test
    public void queryByCid() {
        CategoryVo categoryVo = hbookCategoryBiz.queryByCid(8);
        System.out.println(categoryVo);
    }
}

运行结果：

        案例1：

         案例2：

OK