Mybatis关联关系映射

最新推荐文章于 2023-05-18 17:07:18 发布

原创最新推荐文章于 2023-05-18 17:07:18 发布 · 169 阅读

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CC 4.0 BY-SA版权

本文深入探讨了一对多和多对多关联关系在MyBatis中的实现方式，包括实体类设计、Mapper接口及XML配置，以及如何通过逆向生成工具简化开发流程。

目标
1、一对多关联关系
2、多对多关联关系

1、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
gengar

 <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_book_category" domainObjectName="HbookCategory"
               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>

创建OrderVo类继承原有的实体类

package com.chenkang.model.vo;

import com.chenkang.model.Order;
import com.chenkang.model.OrderItem;

import java.util.ArrayList;
import java.util.List;

/**
 * @author陈康
 * @site www.chenkang.com
 * @company xxx公司
 * @create 2019-10-23 18:41
 */
public class OrderVo  extends Order {
    private List<OrderItem> orderItems = new ArrayList<>();

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

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

OrderItemVo

package com.chenkang.model.vo;

import com.chenkang.model.Order;
import com.chenkang.model.OrderItem;

/**
 * @author陈康
 * @site www.chenkang.com
 * @company xxx公司
 * @create 2019-10-23 18:43
 */
public class OrderItemVo extends OrderItem {
       private Order order;

    public Order getOrder() {
        return order;
    }

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

在OrderMapper中设置一个方法来查询两张表（一对多）

  List<OrderVo>selectByOrderId(@Param("orderId") Integer orderId);

在OrderMapper.xml中配置(一对多)

<resultMap id="OrderVoMap" type="com.chenkang.model.vo.OrderVo">
<result property="orderId" column="order_id"></result>
    <result property="orderNo" column="order_no"></result>
    <collection property="orderItems" ofType="com.chenkang.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="selectByOrderId" resultMap="OrderVoMap" parameterType="java.lang.Integer" >
   select * from t_hibernate_order o,t_hibernate_order_item oi where o.order_id=oi.oid
and oi.oid = #{orderId}
  </select>

OrderItemMapper.java（多对一）

 List<OrderItemVo>selectByOrderItemId(@Param("orderItemId") Integer orderItemId);

在OrderItemMapper.xml中配置(多对一)

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


<select id="selectByOrderItemId" 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>

service层
OneToManyService接口类

package com.chenkang.service;

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

import java.util.List;

/**
 * @author陈康
 * @site www.chenkang.com
 * @company xxx公司
 * @create 2019-10-23 19:07
 */
public interface OneToManyService {

    List<OrderVo> selectByOrderId(Integer orderId);
    List<OrderItemVo>selectByOrderItemId(Integer orderItemId);
}

OneToManyServiceImpl实现service接口

package com.chenkang.service.impl;

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

import java.util.List;

/**
 * @author陈康
 * @site www.chenkang.com
 * @company xxx公司
 * @create 2019-10-23 19:23
 */
@Service
public class OneToManyServiceImpl implements OneToManyService {
    @Autowired
    private OrderItemMapper orderItemMapper;
    @Autowired
    private OrderMapper orderMapper;
    @Override
    public List<OrderVo> selectByOrderId(Integer orderId) {
        return orderMapper.selectByOrderId(orderId);
    }

    @Override
    public List<OrderItemVo> selectByOrderItemId(Integer orderItemId) {
        return orderItemMapper.selectByOrderItemId(orderItemId);
    }
}

测试：

OneToManyServiceImplTest

package com.chenkang.service.impl;

import com.chenkang.SpringBaseTest;
import com.chenkang.model.OrderItem;
import com.chenkang.model.vo.OrderItemVo;
import com.chenkang.model.vo.OrderVo;
import com.chenkang.service.OneToManyService;
import org.junit.Test;
import org.springframework.beans.factory.annotation.Autowired;

import java.util.List;

import static org.junit.Assert.*;

/**
 * @author陈康
 * @site www.chenkang.com
 * @company xxx公司
 * @create 2019-10-23 19:25
 */
public class OneToManyServiceImplTest extends SpringBaseTest {
@Autowired
private OneToManyService oneToManyService;
    @Test
    public void selectByOrderId() {
        List<OrderVo> orderVos = oneToManyService.selectByOrderId(8);
        OrderVo orderVo = orderVos.get(0);
        System.out.println(orderVo);
        List<OrderItem> orderItems = orderVo.getOrderItems();
        System.out.println(orderItems);
    }

    @Test
    public void selectByOrderItemId() {
        List<OrderItemVo> orderItemVos = oneToManyService.selectByOrderItemId(36);
        OrderItemVo orderItemVo = orderItemVos.get(0);
        System.out.println(orderItemVo);
        System.out.println(orderItemVo.getOrder());
    }
}

在这里插入图片描述

2.多对多

HbookVo

package com.chenkang.model.vo;

import com.chenkang.model.Category;
import com.chenkang.model.Hbook;

import java.util.ArrayList;
import java.util.List;

/**
 * @author陈康
 * @site www.chenkang.com
 * @company xxx公司
 * @create 2019-10-23 19:39
 */
public class HbookVo extends Hbook {
    private List<Category> categories = new ArrayList<>();

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

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

CategoryVo

package com.chenkang.model.vo;

import com.chenkang.model.Category;
import com.chenkang.model.Hbook;

import java.util.ArrayList;
import java.util.List;

/**
 * @author陈康
 * @site www.chenkang.com
 * @company xxx公司
 * @create 2019-10-23 19:41
 */
public class CategoryVo extends Category {
    private List<Hbook>hbooks = new ArrayList<>();

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

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

BookCategoryMapper
在接口类中设置方法，以便后面测试

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

BookCategoryMapper.xml

<resultMap id="CategoryVoMap" type="com.chenkang.model.vo.CategoryVo">
    <result property="categoryId" column="category_id"></result>
    <result property="categoryName" column="category_name"></result>
    <collection property="hbooks" ofType="com.chenkang.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="selectByCid" 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 and bc.cid=c.category_id
  and c.category_id = #{cid}
  </select>

HbookMapper

  HbookVo selectByBid(@Param("bid") Integer bid);

HbookMapper.XML

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

    </collection>


<select id="selectByBid" 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 and bc.cid=c.category_id
  and b.book_id = #{bid}
  </select>

Service层
ManyToManyService

package com.chenkang.service;

import com.chenkang.model.Category;
import com.chenkang.model.Hbook;
import com.chenkang.model.vo.CategoryVo;
import com.chenkang.model.vo.HbookVo;
import org.apache.ibatis.annotations.Param;
import org.springframework.stereotype.Service;

/**
 * @author陈康
 * @site www.chenkang.com
 * @company xxx公司
 * @create 2019-10-23 20:09
 */
public interface ManyToManyService {
    HbookVo selectByBid(Integer bid);
    CategoryVo selectByCid(Integer cid);
}

去实现接口中的方法
ManyToManyServiceimpl

package com.chenkang.service.impl;

import com.chenkang.mapper.CategoryMapper;
import com.chenkang.mapper.HbookMapper;
import com.chenkang.model.Category;
import com.chenkang.model.Hbook;
import com.chenkang.model.vo.CategoryVo;
import com.chenkang.model.vo.HbookVo;
import com.chenkang.service.ManyToManyService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;

/**
 * @author陈康
 * @site www.chenkang.com
 * @company xxx公司
 * @create 2019-10-23 20:10
 */
@Service
public class ManyToManyServiceImpl implements ManyToManyService {
    @Autowired
    private HbookMapper hbookMapper;
    @Autowired
    private CategoryMapper categoryMapper;
    @Override
    public HbookVo selectByBid(Integer bid) {
        return hbookMapper.selectByBid(bid);
    }

    @Override
    public CategoryVo selectByCid(Integer cid) {
        return categoryMapper.selectByCid(cid);
    }
}

测试：

package com.chenkang.service.impl;

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

import static org.junit.Assert.*;

/**
 * @author陈康
 * @site www.chenkang.com
 * @company xxx公司
 * @create 2019-10-23 20:13
 */
public class ManyToManyServiceImplTest extends SpringBaseTest {
@Autowired
private ManyToManyService manyToManyService;
    @Test
    public void selectByBid() {
        HbookVo hbookVo = manyToManyService.selectByBid(8);
        System.out.println(hbookVo);
        for (Category category : hbookVo.getCategories()) {
            System.out.println(category);
        }
    }

    @Test
    public void selectByCid() {
        CategoryVo categoryVo = manyToManyService.selectByCid(8);
        System.out.println(categoryVo);
        for (Hbook hbook : categoryVo.getHbooks()) {
            System.out.println(hbook);

        }
    }
}

在这里插入图片描述