Mybatis的关联关系

1、通过 mybatis-generator 插件生成dao、mapper、model

1.1 :配置 mybatis-generator 插件生成文件位置

1.2 :修改 generatorConfig.xml 配置文件的生成目录(mapper和model)及对应生成关系

2、修改 Customer、Order 实体类

2.1:实现序列化接口

2.2:建立实体映射关联关系（一对多、多对一）

   #一对多：一个客户对应多个订单
   private List<Order> orders=new ArrayList<Order>();

   #多对一：多个订单对应一个客户（一个订单对应一个客户）
   private Customer customer;

3、配置 mybatis 关联映射

一对多关联关系

一个订单对应多个订单项

先用逆向生成工具生成t_hibernate_order、t_hibernate_order_item(逆向生成，Mybatis入门已经有讲到，点击传送)

OrderVo

package com.Tang.model.vo;

import com.Tang.model.Order;
import com.Tang.model.OrderItem;

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


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.Tang.model.vo;

import com.Tang.model.Order;
import com.Tang.model.OrderItem;

public class OrderItemVo extends OrderItem {
    private Order order;

    public Order getOrder() {
        return order;
    }

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

OrderMapper.xml

<resultMap id="orderVoMap" type="com.Tang.model.vo.OrderVo">
        <result property="orderId" column="order_id"></result>
        <result property="orderNo" column="order_no"></result>
        <collection property="orderItems" ofType="com.Tang.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="selectByOid" 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>

OrderMapper.java

package com.Tang.mapper;

import com.Tang.model.Order;
import com.Tang.model.vo.OrderVo;
import org.apache.ibatis.annotations.Param;
import org.springframework.stereotype.Repository;

@Repository
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 selectByOid(@Param("oid") Integer oid);

}

OrderItemMapper.xml

  <resultMap id="orderItemVoMap" type="com.Tang.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.Tang.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>

OrderItemMapper.java

package com.Tang.mapper;

import com.Tang.model.OrderItem;
import com.Tang.model.vo.OrderItemVo;
import org.apache.ibatis.annotations.Param;
import org.springframework.stereotype.Repository;

@Repository
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 selectByOrderItemId(@Param("orderItemId") Integer orderItemId);
}

One2ManyService.java

package com.Tang.service;

import com.Tang.model.Order;
import com.Tang.model.vo.OrderItemVo;
import com.Tang.model.vo.OrderVo;

public interface One2ManyService {
    OrderVo selectByOid(Integer oid);
    OrderItemVo selectByOrderItemId(Integer orderItemId);
}

One2ManyServiceImpl

package com.Tang.service.impl;

import com.Tang.mapper.OrderItemMapper;
import com.Tang.mapper.OrderMapper;
import com.Tang.model.vo.OrderItemVo;
import com.Tang.model.vo.OrderVo;
import com.Tang.service.One2ManyService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;


@Service
public class One2ManyServiceImpl implements One2ManyService {
    @Autowired
    private OrderMapper orderMapper;
    private OrderItemMapper orderItemMapper;
    @Override
    public OrderVo selectByOid(Integer oid) {
        return orderMapper.selectByOid(oid);
    }

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

One2ManyServiceImplTest.java

package com.Tang.service.impl;

import com.Tang.SpringJunitBaseTest;
import com.Tang.model.Order;
import com.Tang.model.OrderItem;
import com.Tang.model.vo.OrderItemVo;
import com.Tang.model.vo.OrderVo;
import com.Tang.service.One2ManyService;
import org.junit.Test;
import org.springframework.beans.factory.annotation.Autowired;

import static org.junit.Assert.*;

public class One2ManyServiceImplTest extends SpringJunitBaseTest {
    @Autowired
    private One2ManyService one2ManyService;

    @Test
    public void queryOrderVoByOrderId() {
        OrderVo orderVo = this.one2ManyService.queryOrderVoByOrderId(10);
        System.out.println(orderVo);
        for (OrderItem orderItem : orderVo.getOrderItems()) {
            System.out.println(orderItem);
        }
    }

    @Test
    public void queryOrderItemVoByOrderItemId() {
        OrderItemVo orderItemVo = this.one2ManyService.queryOrderItemVoByOrderItemId(49);
        System.out.println(orderItemVo);
        System.out.println(orderItemVo.getOrder());
    }
}

多对多关联关系

先用逆向生成工具生成t_hibernate_book、t_hibernate_book_category、t_hibernate_category（书籍表、书籍类别表、中间表）

多对多就是指一本书可以有多个类别，一个类别又可以对应多本书

HbookVo

package com.Tang.model.vo;

import com.Tang.model.Category;
import com.Tang.model.Hbook;

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

	
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.Tang.model.vo;

import com.Tang.model.Category;
import com.Tang.model.Hbook;

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

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;
    }
}

HbookCategoryMapper.xml

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

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

HbookCategoryMapper

package com.Tang.mapper;

import com.Tang.model.Category;
import com.Tang.model.Hbook;
import com.Tang.model.HbookCategory;
import com.Tang.model.vo.CategoryVo;
import com.Tang.model.vo.HbookVo;
import org.apache.ibatis.annotations.Param;
import org.springframework.stereotype.Repository;

import java.util.List;

@Repository
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);
}

Many2ManyService

package com.Tang.service;

import com.Tang.model.Category;
import com.Tang.model.Hbook;
import com.Tang.model.vo.CategoryVo;
import com.Tang.model.vo.HbookVo;
import org.apache.ibatis.annotations.Param;


public interface Many2ManyService {
    HbookVo queryByBookId(Integer bookId);

    CategoryVo queryByCid(Integer cid);
}

Many2ManyServiceImpl

package com.Tang.service.impl;

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

@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);
    }
}

Many2ManyServiceImplTest

package com.Tang.service.impl;

import com.Tang.SpringJunitBaseTest;
import com.Tang.model.Category;
import com.Tang.model.Hbook;
import com.dTangj.model.vo.CategoryVo;
import com.Tang.model.vo.HbookVo;
import com.Tang.service.Many2ManyService;
import org.junit.Test;
import org.springframework.beans.factory.annotation.Autowired;

import static org.junit.Assert.*;

public class Many2ManyServiceImplTest extends SpringJunitBaseTest {
    @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);
        }
    }

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

    }

}