• Mybatis关联关系映射

    一、一对多

    1、首先使用Mybatis逆向工程生成t_hibernate_order、t_hibernate_order_item两张表的代码

    model层和Mapper层

    2、建立vo类，vo类能够定义t_hibernate_order表里所没有的属性

    vo类不仅拿到当前表的所有信息，还能拿到相关联表的所有信息

    两个表之间的关系：

                 1、一个订单有多个订单详情表

                 2、一个订单详情只有一个订单

    OrderVo：

    1. package com.zjy.model;
    2.  
    3. import java.util.List;
    4.  
    5. /**
    6.  * @author小朱
    7.  * @site Bi8boYin
    8.  * @company xxx公司
    9.  * @create  2022-08-15 19:27
    10.  */
    11.  
    12.  
    13. //vo类不仅拿到当前表的所有信息，还能拿到相关联表的所有信息
    14. public class OrderVo extends Order {
    15.  
    16.     //通过订单号查询订单的详细信息以及所有订单项的信息
    17.  
    18.     private List orderItems;
    19.  
    20.  
    21.     public List getOrderItems() {
    22.         return orderItems;
    23.     }
    24.  
    25.     public void setOrderItems(List orderItems) {
    26.         this.orderItems = orderItems;
    27.     }
    28. }

    OrderItemVo： 

    1. package com.zjy.model;
    2.  
    3. /**
    4.  * @author小朱
    5.  * @site Bi8boYin
    6.  * @company xxx公司
    7.  * @create  2022-08-15 19:35
    8.  */
    9.  
    10.  
    11. public class OrderItemVo extends OrderItem{
    12.  
    13.     private Order order;
    14.  
    15.  
    16.     public Order getOrder() {
    17.         return order;
    18.     }
    19.  
    20.     public void setOrder(Order order) {
    21.         this.order = order;
    22.     }
    23. }

    3、在OderMapper.xml中映射实体类resultMap以及对应的方法

    1. <resultMap id="OrderVoMap" type="com.zjy.model.OrderVo" >
    2.  
    3.     <result property="orderId" column="order_id">result>
    4.     <result property="orderNo" column="order_no">result>
    5.     <collection property="orderItems" ofType="com.zjy.model.OrderItem">
    6.       <result property="orderItemId" column="order_item_id">result>
    7.       <result property="oid" column="oid">result>
    8.       <result property="productId" column="product_id">result>
    9.       <result property="quantity" column="quantity">result>
    10.     collection>
    11.   resultMap>
    12.  
    13.  
    14.  
    15.  <select id="queryOrderVoByOrderId" resultMap="OrderVoMap" parameterType="java.lang.Integer" >
    16.  
    17.   select * from t_hibernate_order o,t_hibernate_order_item oi
    18.   where o.order_id = oi.oid
    19.   and o.order_id = #{orderId}
    20. select>

    OrderItemMapper.xml

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

     

    4、在对应的OrderMapper.java和OrderItemsMapper.java中配置出对应的方法：

     

    注意：该方法的的返回值一定是vo类，因为我们在xml中resultMap节点里包含了数据库表里不包含的字段

     

    OrderMapper.java

    OrderVo queryOrderItemVoByOrderItemId(Integer orderItemId);

    OrderItemsMapper.java 

    OrderItemVo queryOrderItemVoByOrderItemId(Integer orderItemId);

    5、建立业务类和业务实体类

    OrderBiz

    1. package com.zjy.biz;
    2.  
    3. import com.zjy.model.Order;
    4. import org.apache.ibatis.annotations.Param;
    5.  
    6. /**
    7.  * @author小朱
    8.  * @site Bi8boYin
    9.  * @company xxx公司
    10.  * @create  2022-08-15 19:58
    11.  */
    12. public interface OrderBiz {
    13.     int deleteByPrimaryKey(Integer orderId);
    14.  
    15.     int insert(Order record);
    16.  
    17.     int insertSelective(Order record);
    18.  
    19.     Order selectByPrimaryKey(Integer orderId);
    20.  
    21.     Order queryOrderVoByOrderId(@Param("orderId") Integer orderId);
    22.  
    23.     int updateByPrimaryKeySelective(Order record);
    24.  
    25.     int updateByPrimaryKey(Order record);
    26. }

    OrderBizImpl

    1. package com.zjy.biz.impl;
    2.  
    3. import com.zjy.biz.OrderBiz;
    4. import com.zjy.mapper.OrderMapper;
    5. import com.zjy.model.Order;
    6. import org.springframework.beans.factory.annotation.Autowired;
    7. import org.springframework.stereotype.Service;
    8.  
    9. /**
    10.  * @author小朱
    11.  * @site Bi8boYin
    12.  * @company xxx公司
    13.  * @create  2022-08-15 20:00
    14.  */
    15.  
    16. @Service
    17. public class OrderBizImpl  implements OrderBiz {
    18.     @Autowired
    19.     private OrderMapper orderMapper;
    20.     @Override
    21.     public int deleteByPrimaryKey(Integer orderId) {
    22.         return 0;
    23.     }
    24.  
    25.     @Override
    26.     public int insert(Order record) {
    27.         return 0;
    28.     }
    29.  
    30.     @Override
    31.     public int insertSelective(Order record) {
    32.         return 0;
    33.     }
    34.  
    35.     @Override
    36.     public Order selectByPrimaryKey(Integer orderId) {
    37.         return null;
    38.     }
    39.  
    40.     @Override
    41.     public Order queryOrderVoByOrderId(Integer orderId) {
    42.         return orderMapper.queryOrderVoByOrderId(orderId);
    43.     }
    44.  
    45.     @Override
    46.     public int updateByPrimaryKeySelective(Order record) {
    47.         return 0;
    48.     }
    49.  
    50.     @Override
    51.     public int updateByPrimaryKey(Order record) {
    52.         return 0;
    53.     }
    54. }

    6、编写测试类

    1. package com.zjy.biz.impl;
    2.  
    3. import com.zjy.biz.OrderBiz;
    4. import org.junit.Test;
    5. import org.junit.runner.RunWith;
    6. import org.springframework.beans.factory.annotation.Autowired;
    7. import org.springframework.test.context.ContextConfiguration;
    8. import org.springframework.test.context.junit4.SpringJUnit4ClassRunner;
    9.  
    10. /**
    11.  * @author小朱
    12.  * @site Bi8boYin
    13.  * @company xxx公司
    14.  * @create  2022-08-15 20:09
    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.  
    24.  
    25.     @Test
    26.     public void queryOrderVoByOrderId() {
    27.         orderBiz.queryOrderVoByOrderId(9);
    28.     }
    29.  
    30.  
    31. }

    两张表所对应的关系：通过订单id能够查询出订单详情，通过订单详情也能找到该条订单的id

     

     

     

    二、多对多

    1、多对多关系就是和一对多的关系的大同小异，只是多对多的关系可以看成两个一对多关系。

               2、多对多关系的配置的步骤和一对多关系配置是一样的：（以书籍表、类别表以及书籍类别表为例）

             2.1:首先先用逆向生成工具生成t_hibernate_book、t_hibernate_book_category、t_hibernate_category，这两张表对应的model与mapper

    1.      <table schema="" tableName="t_hibernate_book" domainObjectName="HBook"
    2.                enableCountByExample="false" enableDeleteByExample="false"
    3.                enableSelectByExample="false" enableUpdateByExample="false">
    4.             
    5.             
    6.             
    7.             
    8.         table>
    9.  
    10.  
    11.         <table schema="" tableName="t_hibernate_book_category" domainObjectName="HBookC"
    12.                enableCountByExample="false" enableDeleteByExample="false"
    13.                enableSelectByExample="false" enableUpdateByExample="false">
    14.             
    15.             
    16.             
    17.             
    18.         table>
    19.  
    20.  
    21.  
    22.         <table schema="" tableName="t_hibernate_category" domainObjectName="HCate"
    23.                enableCountByExample="false" enableDeleteByExample="false"
    24.                enableSelectByExample="false" enableUpdateByExample="false">
    25.             
    26.             
    27.             
    28.             
    29.         table>

                      2.2在对应的HbookCategoryMapper.xml配置resultMap节点以及对应的方法：（为什么只在HbookCategoryMapper.xml中进行配置，因为只是一个中间表，可以起到一个连接的动作）：

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

     2.3:在对应的HbookCategoryMapper.java文件中写好方法：

    1. package com.zjy.mapper;
    2.  
    3. import com.zjy.model.HBookC;
    4. import com.zjy.vo.HBookVo;
    5. import com.zjy.vo.HCateVo;
    6. import org.apache.ibatis.annotations.Param;
    7.  
    8. public interface HBookCMapper {
    9.     int deleteByPrimaryKey(Integer bcid);
    10.  
    11.     int insert(HBookC record);
    12.  
    13.     int insertSelective(HBookC record);
    14.  
    15.     HBookC selectByPrimaryKey(Integer bcid);
    16.  
    17.     int updateByPrimaryKeySelective(HBookC record);
    18.  
    19.     int updateByPrimaryKey(HBookC record);
    20.  
    21.  
    22.     HBookVo queryByBookId(@Param("bookId") Integer bookId);
    23.  
    24.     HCateVo queryByCid(@Param("cid") Integer cid);
    25.  
    26.  
    27. }

      2.4之后到service层中接口和实现类中写好方法

    Many2ManyService：
    1. package com.zjy.www.service;
    2.  
    3. import com.zjy.www.vo.HBookVo;
    4. import com.zjy.www.vo.HCateVo;
    5.  
    6. public interface Many2ManyService {
    7.  
    8.     HBookVo queryByBookId(Integer bookId);
    9.  
    10.     HCateVo queryByCid(Integer cid);
    11.  
    12. }
    Many2ManyServiceImpl：
    1. package com.zjy.www.service.impl;
    2.  
    3. import com.zjy.www.mapper.HBookCMapper;
    4. import com.zjy.www.service.Many2ManyService;
    5. import com.zjy.www.vo.HBookVo;
    6. import com.zjy.www.vo.HCateVo;
    7. import org.springframework.beans.factory.annotation.Autowired;
    8. import org.springframework.stereotype.Service;
    9.  
    10. @Service
    11. public class Many2ManyServiceImpl implements Many2ManyService {
    12.     @Autowired
    13.     private HBookCMapper hBookCMapper;
    14.     @Override
    15.     public HBookVo queryByBookId(Integer bookId) {
    16.         return hBookCMapper.queryByBookId(bookId);
    17.     }
    18.  
    19.     @Override
    20.     public HCateVo queryByCid(Integer cid) {
    21.         return hBookCMapper.queryByCid(cid);
    22.     }
    23. }

      2.5:之后配置两个表之间的关系，建立vo类：

    HBookVo：

    1. package com.zjy.www.vo;
    2.  
    3. import com.zjy.www.model.HBook;
    4. import com.zjy.www.model.HBookC;
    5. import com.zjy.www.model.HCate;
    6.  
    7. import java.util.ArrayList;
    8. import java.util.List;
    9.  
    10. public class HBookVo  extends HBook {
    11.  
    12.  
    13.     private List<HCate> categories = new ArrayList<>();
    14.  
    15.     public List<HCate> getCategories() {
    16.         return categories;
    17.     }
    18.  
    19.     public void setCategories(List<HCate> categories) {
    20.         this.categories = categories;
    21.     }
    22.  
    23.  
    24. }

    HBookC：

    1. package com.zjy.www.vo;
    2.  
    3. import com.zjy.www.model.HBook;
    4. import com.zjy.www.model.HCate;
    5.  
    6. import java.util.ArrayList;
    7. import java.util.List;
    8.  
    9. public class HCateVo extends HCate {
    10.  
    11.  
    12.     private List hbooks = new ArrayList<>();
    13.  
    14.     public List getHbooks() {
    15.         return hbooks;
    16.     }
    17.  
    18.     public void setHbooks(List hbooks) {
    19.         this.hbooks = hbooks;
    20.     }
    21.  
    22.  
    23.     @Override
    24.     public String toString() {
    25.         return "HCateVo{" +
    26.                 "hbooks=" + hbooks +
    27.                 '}';
    28.     }
    29. }

     2.6：编写测试类:

    1. package com.zjy.www.service.impl;
    2.  
    3. import com.zjy.www.model.HBook;
    4. import com.zjy.www.model.HCate;
    5. import com.zjy.www.service.Many2ManyService;
    6. import com.zjy.www.vo.HBookVo;
    7. import com.zjy.www.vo.HCateVo;
    8. import junit.framework.TestCase;
    9. import org.junit.Test;
    10. import org.junit.runner.RunWith;
    11. import org.springframework.beans.factory.annotation.Autowired;
    12. import org.springframework.test.context.ContextConfiguration;
    13. import org.springframework.test.context.junit4.SpringJUnit4ClassRunner;
    14.  
    15. @RunWith(SpringJUnit4ClassRunner.class)
    16. @ContextConfiguration(locations={"classpath:applicationContext.xml"})
    17. public class Many2ManyServiceImplTest extends TestCase {
    18.  
    19.     @Autowired
    20.     private Many2ManyService many2ManyService;
    21.  
    22.     @Test
    23.     public void queryByBookId() {
    24.         HBookVo hbookVo = many2ManyService.queryByBookId(8);
    25.         System.out.println(hbookVo);
    26.         for (HCate category : hbookVo.getCategories()) {
    27.             System.out.println(category);
    28.         }
    29.     }
    30.  
    31.     @Test
    32.     public void queryByCid() {
    33.         HCateVo categoryVo = many2ManyService.queryByCid(8);
    34.         System.out.println(categoryVo);
    35.         for (HBook hbook : categoryVo.getHbooks()) {
    36.             System.out.println(hbook);
    37.         }
    38.  
    39.     }
    40. }

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  • 原文地址：https://blog.csdn.net/m0_67477525/article/details/126354478