关联关系映射

本次目标：

一、一对多关联关系

二、多对多关联关系

本次目标：

一对多关联关系
多对多关联关系

一、一对多关联关系

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

t_hibernate_order:

t_hibernate_order_item :

知道表之后我们直接生成相对应的对象：

先把这几个地方改一下：（如果不懂的如何生成通用的增删改查可以看看这里，里面有些哦）

还有下面的那个表名也要改一下：

generatorConfig.xml：


generatorConfiguration PUBLIC "-//mybatis.org//DTD MyBatis Generator Configuration 1.0//EN"
        "http://mybatis.org/dtd/mybatis-generator-config_1_0.dtd" >
<generatorConfiguration>
    
    <properties resource="jdbc.properties"/>
 
    
    <classPathEntry location="D:\\maven\\mvn_repository\\mysql\\mysql-connector-java\\5.1.44\\mysql-connector-java-5.1.44.jar"/>
 
    
    <context id="infoGuardian">
        
        <commentGenerator>
            <property name="suppressAllComments" value="true"/>
            <property name="suppressDate" value="true"/> 
        commentGenerator>
 
        
        <jdbcConnection driverClass="${jdbc.driver}"
                        connectionURL="${jdbc.url}" userId="${jdbc.username}" password="${jdbc.password}"/>
 
        
        <javaTypeResolver>
            
            <property name="forceBigDecimals" value="false"/>
        javaTypeResolver>
 
        
        
        
        <javaModelGenerator targetPackage="com.ps.ssm.model"
                            targetProject="src/main/java">
            
            <property name="enableSubPackages" value="false"/>
            
            <property name="constructorBased" value="true"/>
            
            <property name="trimStrings" value="false"/>
            
            <property name="immutable" value="false"/>
        javaModelGenerator>
 
        
        <sqlMapGenerator targetPackage="com.ps.ssm.mapper"
                         targetProject="src/main/java">
            
            <property name="enableSubPackages" value="false"/>
        sqlMapGenerator>
 
        
        
        
        
        <javaClientGenerator targetPackage="com.ps.ssm.mapper"
                             targetProject="src/main/java" type="XMLMAPPER">
            
            <property name="enableSubPackages" value="false"/>
        javaClientGenerator>
 
        
        
        
        
        
        
        
        
        
        
        
        
        
 
 
        <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="Item"
               enableCountByExample="false" enableDeleteByExample="false"
               enableSelectByExample="false" enableUpdateByExample="false">
        table>
 
    context>
generatorConfiguration>

生成后：

OrderBiz:


package com.ps.ssm.biz;
 
import com.ps.ssm.model.Book;
import com.ps.ssm.model.BookVo;
import com.ps.ssm.model.Order;
import com.ps.ssm.model.vo.OrderVo;
import com.ps.ssm.util.PageBean;
import org.apache.ibatis.annotations.Param;
 
import java.util.List;
import java.util.Map;
 
public interface OrderBiz {
    int deleteByPrimaryKey(Integer orderId);
 
    int insert(Order record);
 
    int insertSelective(Order record);
 
    Order selectByPrimaryKey(Integer orderId);
 
    OrderVo queryOrderVoByOrderId(Integer orderId);
 
    int updateByPrimaryKeySelective(Order record);
 
    int updateByPrimaryKey(Order record);
}

ItemBiz


package com.ps.ssm.biz;
 
import com.ps.ssm.model.Item;
import com.ps.ssm.model.vo.ItemVo;
import org.apache.ibatis.annotations.Param;
 
public interface ItemBiz {
    int deleteByPrimaryKey(Integer ItemId);
 
    int insert(Item record);
 
    int insertSelective(Item record);
 
    Item selectByPrimaryKey(Integer ItemId);
 
    ItemVo queryItemVoByItemId(Integer ItemId);
 
    int updateByPrimaryKeySelective(Item record);
 
    int updateByPrimaryKey(Item record);
}

OrderBizImpl


package com.ps.ssm.biz.impl;
 
import com.ps.ssm.biz.OrderBiz;
import com.ps.ssm.mapper.OrderMapper;
import com.ps.ssm.model.Order;
import com.ps.ssm.model.vo.OrderVo;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;
 
@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;
    }
}

ItemBizImpl:


package com.ps.ssm.biz.impl;
 
import com.ps.ssm.biz.ItemBiz;
import com.ps.ssm.mapper.ItemMapper;
import com.ps.ssm.model.Item;
import com.ps.ssm.model.vo.ItemVo;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;
 
@Service
public class ItemBizImpl implements ItemBiz {
    @Autowired
    private ItemMapper ItemMapper;
    @Override
    public int deleteByPrimaryKey(Integer ItemId) {
        return 0;
    }
 
    @Override
    public int insert(Item record) {
        return 0;
    }
 
    @Override
    public int insertSelective(Item record) {
        return 0;
    }
 
    @Override
    public Item selectByPrimaryKey(Integer ItemId) {
        return null;
    }
 
    @Override
    public ItemVo queryOrderItemVoByOrderItemId(Integer ItemId) {
        return ItemMapper.queryOrderItemVoByItemId(ItemId);
    }
 
    @Override
    public int updateByPrimaryKeySelective(Item record) {
        return 0;
    }
 
    @Override
    public int updateByPrimaryKey(Item record) {
        return 0;
    }
}

OrderVo :


package com.ps.vo;
 
import com.ps.model.Order;
import com.ps.model.OrderItem;
 
import java.util.ArrayList;
import java.util.List;
 
public class OrderVo extends Order {
    private List orderItems = new ArrayList<>();
 
    public List getOrderItems() {
        return orderItems;
    }
 
    public void setOrderItems(List orderItems) {
        this.orderItems = orderItems;
    }
 
 
    @Override
    public String toString() {
        return "OrderVo{" +
                "orderItems=" + orderItems +
                '}';
    }
}

ItemVo :


 
package com.ps.vo;
 
import com.ps.model.Order;
import com.ps.model.OrderItem;
 
public class ItemVo extends OrderItem {
    private Order order;
 
    public Order getOrder() {
        return order;
    }
 
    public void setOrder(Order order) {
        this.order = order;
    }
 
 
    @Override
    public String toString() {
        return "OrderItemVo{" +
                "order=" + order +
                '}';
    }
}

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

二、多对多关联关系

比如一本书籍有多个类别，多个类别对多本书

多对多相当于两个一对多


<resultMap id="HbookVoMap" type="com.ps.model.vo.HbookVo">
    <result property="bookId" column="book_id">result>
    <result property="bookName" column="book_name">result>
    <collection property="categories" ofType="com.ps.model.Category">
      <result property="categoryId" column="category_id">result>
      <result property="categoryName" column="category_name">result>
    collection>
  resultMap>
 
  <resultMap id="CategoryVoMap" type="com.ps.model.vo.CategoryVo">
    <result property="categoryId" column="category_id">result>
    <result property="categoryName" column="category_name">result>
    <collection property="hbooks" ofType="com.ps.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.ps.biz.impl;
 
import com.ps.biz.HbookCategoryBiz;
import com.ps.mapper.HbookCategoryMapper;
import com.ps.model.HbookCategory;
import com.ps.model.vo.CategoryVo;
import com.ps.model.vo.HbookVo;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;
 
/**
 * @author 彭于晏
 * @create  2022-08-15 23:30
 */
@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.ps.biz.impl;
 
import com.ps.biz.HbookCategoryBiz;
import com.ps.model.vo.CategoryVo;
import com.ps.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 彭于晏
 * @create  2022-08-15 0:33
 */
@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);
    }
}

queryByBookId结果：

queryByCid效果：

好啦！今天的分享就到这里，我们下次再见！

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原文地址：https://blog.csdn.net/weixin_63531940/article/details/126354295