mybatis高级映射

一对一关联映射

需求：查询订单信息，关联查询用户信息（一个订单对应一个用户）

（1）通过resultType实现

sql语句：

select

orders.* ,

USER.username,

USER. sex  ,

USER.address

FROM orders , USER

WHERE orders.userid = USER .id

创建pojo类

由于orders.java不能全部映射字段，所以要新建pojo

创建一个pojo继承包括查询字段较多的·一个po类

OrdersCustom.java (订单扩展类)

//订单扩展类

public class OrdersCustom extends Orders{

	//添加用户属性

	private String username;

	private String sex;

	private String address;

	public String getUsername() {

		return username;

	}

	public void setUsername(String username) {

		this.username = username;

	}

	public String getSex() {

		return sex;

	}

	public void setSex(String sex) {

		this.sex = sex;

	}

	public String getAddress() {

		return address;

	}

	public void setAddress(String address) {

		this.address = address;

	}

}

mapper.xml文件

<!DOCTYPE mapper

PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"

"http://mybatis.org/dtd/mybatis-3-mapper.dtd">

<mapper namespace="cn.mapper.OrdersMapperCustom">

	<select id="findOrdersUser" parameterType="" resultType="cn.po.OrdersCustom">

		select

		orders.* ,

		USER.username,

		USER. sex  ,

		USER.address

		FROM orders , USER

		WHERE orders.userid = USER .id

	</select>

</mapper>

（2）resultMap实现

sql语句

select

orders.* ,

USER.username,

USER. sex  ,

USER.address

FROM orders , USER

WHERE orders.userid = USER .id

　在orders类中添加user

//用户信息
private User user;

生成get ，set 方法

mapper.xml

	<!-- 定义订单查询关联用户resultMap

	将整合查询结果映射到cn.po.Orders-->

	<resultMap type="cn.po.Orders" id="OrdersUserResultMap">

		<!-- 映射订单信息，非关联  -->

		<!-- id唯一标识，如果有多个配置多个id -->

		<id column="id" property="id"></id>

		<result column=user_id" property="userid"></result>

		<result column=number" property="number"></result>

		<result column=createtime" property="createtime"></result>

		<result column="note" property="note"></result>

		<!-- 配置映射的关联用户信息 -->

		<!-- association用于映射关联查询单个对象的信息

			property 要将关联查询的用户信息映射到Orders的那个属性

		 -->

		<association property="user" javaType="cn.po.User">

			<!-- id关联用户的唯一标识

				colimn 指定唯一标识用户列

				javaType映射到user的那个属性

			 -->

			<id column="user_id" property="id"/>

			<result column="username" property="username"/>

			<result column="sex" property="sex"/>

			<result column="address" property="address"/>

		</association>

	</resultMap>

	<select id="findOrdersUser" parameterType="" resultMap="OrdersUserResultMap">

		select

		orders.* ,

		USER.username,

		USER. sex  ,

		USER.address

		FROM orders , USER

		WHERE orders.userid = USER .id

	</select>

一对多关联映射

需求：查询订单及订单明细（一个订单里有多个商品明细）

sql语句

select

orders.* ,

orderdetail.id orderdetail_id,

orderdetail.items_id,

orderdetail.items_num,

orderdetail.orders_id

FROM orders ,orderdetail

WHERE orderdetail.orders_id = orders.id

在Orders类中添加订单明细（orderdetail.java）的list集合

//订单明细

private List<Orderdetail> orderdetail;

mapper.xml

<resultMap type="cn.po.Orders" id="OrdersOrderdetailResultMap">

		<!-- 映射订单信息，非关联  -->

		<!-- id唯一标识，如果有多个配置多个id -->

		<id column="id" property="id"></id>

		<result column=user_id" property="userid"></result>

		<result column=number" property="number"></result>

		<result column=createtime" property="createtime"></result>

		<result column="note" property="note"></result>

		<!-- 配置映射的关联用户信息 -->

		<!-- collection用于映射关联查询多个记录映射到集合当中

			property 要将关联查询的用户信息映射到Orders的那个属性

		    ofType指定映射到集合属性中类型

		 -->

		 <collection property="orderdetail" ofType="cn.po.Orderdetail">

		 	<id column="orderdetail_id" property="id"></id>

		 	<result column="items_id" property="itemsid"></result>

		 	<result column="items_num" property="itemsnum"></result>

		 	<result column="orders_id" property="ordersid"></result>

		 </collection>

	</resultMap>

	<select id="findOrdersUser" parameterType="" resultMap="OrdersOrderdetailResultMap">

		select

		orders.* ,

		orderdetail.id orderdetail_id,

		orderdetail.items_id,

		orderdetail.items_num,

		orderdetail.orders_id

		FROM orders ,orderdetail

		WHERE orderdetail.orders_id = orders.id

	</select>

巴特西

mybatis高级映射（一对一，一对多）

mybatis高级映射

一对一关联映射

一对多关联映射

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