mybatis 一对一的映射(两种方式)

标签：mybatis

对于一对一的关系映射一共有两种解决方案：

开发步骤：1）写OrdersMapperUser.xml文件 2）编写与xml同名的接口OrdersMapperUser 3)测试

声明：一下xml文件的代码都在<mapper  namespace="cn.itcast.mapper.OrdersMapperUser"></mapper>中

方式一：使用包装类完成映射关系(比较容易理解)

需求：一个订单只对应一个用户

1）编写包装了类OrdersUser继承Orders类 并在OrdersUser中声明User中的属性

public class OrdersUser  extends Orders{
	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;
	}
}

通过select语句查询出orders表中所有的属性以及user表中的属性-->内连接方式(通过外键关联)

<select id="findOrdersUser" resultType="cn.itcast.domain.OrdersUser">
		select orders.*,user.username,user.sex,user.address
		from orders,user
		where orders.user_id=user.id
	</select>

public OrdersUser findOrdersUser();

@Test
	public void testfindOrdersUser(){
		SqlSession sqlSession = sqlSessionFactory.openSession();
		OrdersMapperUser ordersMapperUser = sqlSession.getMapper(OrdersMapperUser.class);
		OrdersUser ordersUser = ordersMapperUser.findOrdersUser();
		System.out.println(ordersUser.getUsername());
	}

方式二:通过resultMap方法

1）xml中配置 对于一对一使用association property对应的是Orders中的user属性 javatype user属性对应的User类型

<!-- ####################################一对一的查询########################################################## -->
	<resultMap type="cn.itcast.domain.Orders" id="ordersUserResultMap">
		<id column="id" property="id"/>
		<result column="number" property="number"/>
		<result column="createtime" property="createtime"/>
		<result column="note" property="note"/>
		<result column="user_id" property="userId"/>
		<association property="user" javaType="cn.itcast.domain.User">
			<id column="id" property="id"/>
			<result column="username" property="username"/>
			<result column="sex" property="sex"/>
			<result column="address" property="address"/>
		</association>
	</resultMap>
	<select id="findOrdersUserResultMap" resultMap="ordersUserResultMap">
		select orders.*,user.username,user.sex,user.address
		from orders,user
		where orders.user_id=user.id
	</select>

public List<Orders> findOrdersUserResultMap();

mybatis 一对一的映射(两种方式)

标签：mybatis

原文地址：http://blog.csdn.net/u014010769/article/details/47302587