Mybatis之关联关系映射

最新推荐文章于 2023-09-04 12:24:43 发布

BK_201H

最新推荐文章于 2023-09-04 12:24:43 发布

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分类专栏： mybatis

本文链接：https://blog.youkuaiyun.com/qq_45105634/article/details/103232243

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本文详细介绍了使用MyBatis实现一对多和多对多关联查询的方法，包括逆向生成工具的使用、实体类和VO类的设计、Mapper文件的配置以及Service层的实现。

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一对多

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
generatorConfig.xml

 <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>

在这里插入图片描述

vo类：为了不破坏本身类的封装性，和数据库里面字段一一映射
OrderVo

package com.bk201.ssm.model.vo;

import com.bk201.ssm.model.Order;
import com.bk201.ssm.model.OrderItem;

import java.util.List;

/**
 * @author bk201
 * @site www.fellingss.com
 * @company
 * @create 2019-11-24 19:03
 */
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

package com.bk201.ssm.model.vo;

import com.bk201.ssm.model.Order;
import com.bk201.ssm.model.OrderItem;

/**
 * @author bk201
 * @site www.fellingss.com
 * @company
 * @create 2019-11-24 19:05
 */
public class OrderItemVo extends OrderItem {
    private Order order;

    public Order getOrder() {
        return order;
    }

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

添加一个映射
OrderMapper.xml

<resultMap id="OrderVoMap" type="com.bk201.ssm.model.vo.OrderVo" >
    <result property="orderId" column="order_id"></result>
    <result property="orderNo" column="order_no"></result>
    <collection property="orderItems" ofType="com.bk201.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>

  <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>

对应添加:
OrderMapper

package com.bk201.ssm.mapper;

import com.bk201.ssm.model.Order;
import com.bk201.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);
}

OrderItemMapper.xml

<resultMap id="OrderItemVoMap" type="com.bk201.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.bk201.ssm.model.Order">
      <result property="orderId" column="order_id"></result>
      <result property="orderNo" column="order_no"></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>

OrderItemMapper

package com.bk201.ssm.mapper;

import com.bk201.ssm.model.OrderItem;
import com.bk201.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);
}

One2ManyService.java

package com.bk201.ssm.service;

import com.bk201.ssm.model.vo.OrderItemVo;
import com.bk201.ssm.model.vo.OrderVo;

/**
 * @author bk201
 * @site www.fellingss.com
 * @company
 * @create 2019-11-24 19:12
 */
public interface One2ManyService {
    OrderVo queryOrderVoByOrderId(Integer orderId);

    OrderItemVo queryOrderItemVoByOrderItemId(Integer orderItemId);
}

One2ManyServiceImpl

package com.bk201.ssm.service.impl;

import com.bk201.ssm.mapper.OrderItemMapper;
import com.bk201.ssm.mapper.OrderMapper;
import com.bk201.ssm.model.vo.OrderItemVo;
import com.bk201.ssm.model.vo.OrderVo;
import com.bk201.ssm.service.One2ManyService;
import org.springframework.beans.factory.annotation.Autowired;

/**
 * @author bk201
 * @site www.fellingss.com
 * @company
 * @create 2019-11-24 19:54
 */
 @Service
public class One2ManyServiceImpl implements One2ManyService {
    @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:
这里记得要在生成的实体类里面写tostring方法
One2ManyServiceImplTest

package com.bk201.ssm.service.impl;

import com.bk201.ssm.SpringBaseTest;
import com.bk201.ssm.model.OrderItem;
import com.bk201.ssm.model.vo.OrderItemVo;
import com.bk201.ssm.model.vo.OrderVo;
import com.bk201.ssm.service.One2ManyService;
import org.junit.Test;
import org.springframework.beans.factory.annotation.Autowired;

/**
 * @author bk201
 * @site www.fellingss.com
 * @company
 * @create 2019-11-24 19:56
 */

public class One2ManyServiceImplTest extends SpringBaseTest {
    @Autowired
    private One2ManyService one2ManyService;
    @Test
    public void queryOrderVoByOrderId() {
        OrderVo orderVo = one2ManyService.queryOrderVoByOrderId(8);
        System.out.println(orderVo.getOrderNo());
        for (OrderItem orderItem : orderVo.getOrderItems()) {
            System.out.println(orderItem);
        }
    }

    @Test
    public void queryOrderItemVoByOrderItemId() {
        OrderItemVo orderItemVo = one2ManyService.queryOrderItemVoByOrderItemId(36);
        System.out.println(orderItemVo);
        System.out.println(orderItemVo.getOrder().getOrderNo());
    }
}

结果图:
在这里插入图片描述

多对多关联关系

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
HbookVo

package com.bk201.ssm.model.vo;

import com.bk201.ssm.model.Category;
import com.bk201.ssm.model.Hbook;

import java.util.List;

/**
 * @author bk201
 * @site www.fellingss.com
 * @company
 * @create 2019-11-24 20:26
 */
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

package com.bk201.ssm.model.vo;

import com.bk201.ssm.model.Category;
import com.bk201.ssm.model.Hbook;

import java.util.List;

/**
 * @author bk201
 * @site www.fellingss.com
 * @company
 * @create 2019-11-24 20:27
 */
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.xml

<resultMap id="HbookVoMap" type="com.bk201.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.bk201.ssm.model.Category">
      <result property="categoryId" column="category_id"></result>
      <result property="categoryName" column="category_name"></result>
    </collection>
  </resultMap>


  <resultMap id="CategoryVoMap" type="com.bk201.ssm.model.vo.CategoryVo">
    <result property="categoryId" column="category_id"></result>
    <result property="categoryName" column="category_name"></result>
    <collection property="hbooks" ofType="com.bk201.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>

<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>

HbookCategoryMapper

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

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

Many2ManyService

package com.bk201.ssm.service;

import com.bk201.ssm.model.vo.CategoryVo;
import com.bk201.ssm.model.vo.HbookVo;

/**
 * @author bk201
 * @site www.fellingss.com
 * @company
 * @create 2019-11-25 9:13
 */
public interface Many2ManyService {

    HbookVo queryByBookId(Integer bookId);

    CategoryVo queryByCid(Integer cid);

}

Many2ManyServiceImpl

package com.bk201.ssm.service.impl;

import com.bk201.ssm.mapper.HbookCategoryMapper;
import com.bk201.ssm.model.vo.CategoryVo;
import com.bk201.ssm.model.vo.HbookVo;
import com.bk201.ssm.service.Many2ManyService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;

/**
 * @author bk201
 * @site www.fellingss.com
 * @company
 * @create 2019-11-25 9:12
 */
@Service
public class Many2ManyServiceImpl implements Many2ManyService {
    @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
Many2ManyServiceImplTest

package com.bk201.ssm.service.impl;

import com.bk201.ssm.SpringBaseTest;
import com.bk201.ssm.model.Category;
import com.bk201.ssm.model.Hbook;
import com.bk201.ssm.model.vo.CategoryVo;
import com.bk201.ssm.model.vo.HbookVo;
import com.bk201.ssm.service.Many2ManyService;
import org.junit.Test;
import org.springframework.beans.factory.annotation.Autowired;

/**
 * @author bk201
 * @site www.fellingss.com
 * @company
 * @create 2019-11-25 9:16
 */
public class Many2ManyServiceImplTest extends SpringBaseTest {
    @Autowired
    private Many2ManyService many2ManyService;
    @Test
    public void queryByBookId() {
        HbookVo hbookVo = many2ManyService.queryByBookId(8);
        System.out.println(hbookVo);
        for (Category category : hbookVo.getCategories()) {
            System.out.println(category.getCategoryName());
        }
    }

    @Test
    public void queryByCid() {
        CategoryVo categoryVo = many2ManyService.queryByCid(8);
        System.out.println(categoryVo.getCategoryName());
        for (Hbook hbook : categoryVo.getHbooks()) {
            System.out.println(hbook.getBookName());
        }
    }
}

运行结果:
在这里插入图片描述