关联关系映射

一对多关联关系

1.使用的五个数据表如下

2.通过resources下的generatorConfig插件生成dao、mapper、model

<?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="D:\\tools\\mvn\\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.xwt.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.xwt.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.xwt.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>
        <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>

具体代码如下：

OrderVo.java

package com.xwt.ssm.model.vo;

import com.xwt.ssm.model.Order;
import com.xwt.ssm.model.OrderItem;
import net.sf.ehcache.store.StoreQuery;

import java.util.List;

public class OrderVo extends Order {
    private List<OrderItem> orderItems;

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

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

OrderItemVo.java

package com.xwt.ssm.model.vo;

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

public class OrderItemVo extends OrderItem{
    private Order order;

    public Order getOrder() {
        return order;
    }

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

OrderMapper.java

package com.xwt.ssm.mapper;

import com.xwt.ssm.model.Order;
import com.xwt.ssm.model.vo.OrderVo;
import org.apache.ibatis.annotations.Param;

public interface OrderMapper {
    int deleteByPrimaryKey(Integer orderId);

    int insert(Order record);

    int insertSelective(Order record);

    Order selectByPrimaryKey(Integer orderId);

    int updateByPrimaryKeySelective(Order record);

    int updateByPrimaryKey(Order record);

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

}

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.xwt.ssm.mapper.OrderMapper" >
  <resultMap id="BaseResultMap" type="com.xwt.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>

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

  <sql id="Base_Column_List" >
    order_id, order_no
  </sql>
  <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.xwt.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.xwt.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.xwt.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.xwt.ssm.model.Order" >
    update t_hibernate_order
    set order_no = #{orderNo,jdbcType=VARCHAR}
    where order_id = #{orderId,jdbcType=INTEGER}
  </update>

  <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>
</mapper>

OrderItemMapper.java

package com.xwt.ssm.mapper;

import com.xwt.ssm.model.OrderItem;
import com.xwt.ssm.model.vo.OrderItemVo;
import org.apache.ibatis.annotations.Param;

public interface OrderItemMapper {
    int deleteByPrimaryKey(Integer orderItemId);

    int insert(OrderItem record);

    int insertSelective(OrderItem record);

    OrderItem selectByPrimaryKey(Integer orderItemId);

    int updateByPrimaryKeySelective(OrderItem record);

    int updateByPrimaryKey(OrderItem record);

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

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.xwt.ssm.mapper.OrderItemMapper" >
  <resultMap id="BaseResultMap" type="com.xwt.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>

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

  <sql id="Base_Column_List" >
    order_item_id, product_id, quantity, oid
  </sql>
  <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.xwt.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.xwt.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.xwt.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.xwt.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>

  <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>
</mapper>

One2Service.java

package com.xwt.ssm.service;

import com.xwt.ssm.model.vo.OrderItemVo;
import com.xwt.ssm.model.vo.OrderVo;
import org.apache.ibatis.annotations.Param;

public interface One2Service {
    OrderVo queryOrderVoByOrderId(Integer orderId);

    OrderItemVo queryOrderItemVoByOrderItemId(Integer orderItemId);
}

One2ServiceImpl.java

package com.xwt.ssm.service.impl;

import com.xwt.ssm.mapper.OrderItemMapper;
import com.xwt.ssm.mapper.OrderMapper;
import com.xwt.ssm.model.vo.OrderItemVo;
import com.xwt.ssm.model.vo.OrderVo;
import com.xwt.ssm.service.One2Service;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;

@Service
public class One2ServiceImpl implements One2Service {
    @Autowired
    private OrderMapper orderMapper;
    @Autowired
    private OrderItemMapper orderItemMapper;
    @Override
    public OrderVo queryOrderVoByOrderId(Integer orderId) {
        return orderMapper.queryOrderVoByOrderId(orderId);
    }

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

测试类One2ServiceImplTest.java

package com.xwt.ssm.service.impl;

import com.xwt.ssm.SpingBaseTest;
import com.xwt.ssm.model.OrderItem;
import com.xwt.ssm.model.vo.OrderItemVo;
import com.xwt.ssm.model.vo.OrderVo;
import com.xwt.ssm.service.One2Service;
import org.junit.Test;
import org.springframework.beans.factory.annotation.Autowired;

import static org.junit.Assert.*;

public class One2ServiceImplTest extends SpingBaseTest {

    @Autowired
    private One2Service one2Service;
    @Test
    // 通过订单查询所有订单项
    public void queryOrderVoByOrderId() {
        OrderVo orderVo=one2Service.queryOrderVoByOrderId(11);
        System.out.println(orderVo.getOrderNo());
        for (OrderItem orderItem : orderVo.getOrderItems()) {
            System.out.println(orderItem);
        }
    }

    @Test
    // 通过订单项查询所属订单
    public void queryOrderItemVoByOrderItemId() {
        OrderItemVo orderItemVo = one2Service.queryOrderItemVoByOrderItemId(50);
        System.out.println(orderItemVo);
        System.out.println(orderItemVo.getOrder().getOrderNo());
    }
}

运行分别如下：

多对多关联关系

HbookVo.java

package com.xwt.ssm.model.vo;

import com.xwt.ssm.model.Category;
import com.xwt.ssm.model.Hbook;

import java.util.List;

public class HbookVo extends Hbook {
    private List<Category> categories;

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

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

CategoryVo .java

package com.xwt.ssm.model.vo;

import com.xwt.ssm.model.Category;
import com.xwt.ssm.model.Hbook;

import java.util.List;

public class CategoryVo extends Category {
    private List<Hbook> hbooks;

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

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

HbookCategoryMapper .java

package com.xwt.ssm.mapper;

import com.xwt.ssm.model.HbookCategory;
import com.xwt.ssm.model.vo.CategoryVo;
import com.xwt.ssm.model.vo.HbookVo;
import org.apache.ibatis.annotations.Param;

public interface HbookCategoryMapper {
    int deleteByPrimaryKey(Integer bcid);

    int insert(HbookCategory record);

    int insertSelective(HbookCategory record);

    HbookCategory selectByPrimaryKey(Integer bcid);

    int updateByPrimaryKeySelective(HbookCategory record);

    int updateByPrimaryKey(HbookCategory record);

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

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

HbookCategoryMapper.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.xwt.ssm.mapper.HbookCategoryMapper" >
  <resultMap id="BaseResultMap" type="com.xwt.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>

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

  <resultMap id="CategoryVoMap" type="com.xwt.ssm.model.vo.CategoryVo" >
    <result property="categoryId" column="category_id"></result>
    <result property="categoryName" column="category_name"></result>
    <collection property="hbooks" ofType="com.xwt.ssm.model.Hbook">
      <result property="bookId" column="book_id"></result>
      <result property="bookName" column="book_name"></result>
      <result property="price" column="price"></result>
    </collection>
  </resultMap>

  <sql id="Base_Column_List" >
    bcid, bid, cid
  </sql>
  <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.xwt.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.xwt.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.xwt.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.xwt.ssm.model.HbookCategory" >
    update t_hibernate_book_category
    set bid = #{bid,jdbcType=INTEGER},
      cid = #{cid,jdbcType=INTEGER}
    where bcid = #{bcid,jdbcType=INTEGER}
  </update>

  <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>
</mapper>

Many2Service .java

package com.xwt.ssm.service;

import com.xwt.ssm.model.vo.CategoryVo;
import com.xwt.ssm.model.vo.HbookVo;
import org.apache.ibatis.annotations.Param;

public interface Many2Service {
    HbookVo queryByBookId(Integer bookId);

    CategoryVo queryByCid(Integer cid);
}

Many2ServiceImpl .java

package com.xwt.ssm.service.impl;

import com.xwt.ssm.mapper.HbookCategoryMapper;
import com.xwt.ssm.model.Hbook;
import com.xwt.ssm.model.vo.CategoryVo;
import com.xwt.ssm.model.vo.HbookVo;
import com.xwt.ssm.service.Many2Service;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;

@Service
public class Many2ServiceImpl implements Many2Service {
    @Autowired
    private HbookCategoryMapper hbookCategoryMapper;

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

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

测试类Many2ServiceImplTest .java

package com.xwt.ssm.service.impl;

import com.xwt.ssm.SpingBaseTest;
import com.xwt.ssm.model.Category;
import com.xwt.ssm.model.Hbook;
import com.xwt.ssm.model.vo.CategoryVo;
import com.xwt.ssm.model.vo.HbookVo;
import com.xwt.ssm.service.Many2Service;
import org.junit.Test;
import org.springframework.beans.factory.annotation.Autowired;

import static org.junit.Assert.*;

public class Many2ServiceImplTest extends SpingBaseTest {

    @Autowired
    private Many2Service many2Service;
    @Test
    // 一本书对应多种类别
    public void queryByBookId() {
        HbookVo hbookVo = many2Service.queryByBookId(8);
        System.out.println(hbookVo.getBookName());
        for (Category category : hbookVo.getCategories()) {
            System.out.println(category.getCategoryName());
        }
    }

    @Test
    // 一种类别对应多本书
    public void queryByCid() {
        CategoryVo category=many2Service.queryByCid(9);
        System.out.println(category.getCategoryName());
        for (Hbook hbook : category.getHbooks()) {
            System.out.println(hbook.getBookName());
        }
    }
}

运行分别如下：