1、举例说明：多个demo对应demo1实体对象；
package com.liwei.shiro.model;
public class Demo {
private String name;
private Integer age;
private String password;
private Demo1 d1;
省略set，get方法
}
}
2、创建demo1对象；
public class Demo1 {
private String name;
public void setName(String name) {
this.name = name;
}
public String getName() {
return name;
}
}
3、创建demo的dao层，创建service。此处省略。
配置dao的代理对象mapper文件。
<resultMap type="cn.itcast.domain.Demo" id="ordersUserResultMap">
<id column="id" property="id"/>
<result column="name" property="name"/>
<result column="age'" property="age"/>
<result column="password" property="password"/>
4、<association property="demo1" javaType="cn.itcast.domain.Demo1">
<id column="id" property="id"/>
<result column="name" property="name"/>
</association>
</resultMap>
5、此处resultMap对应 id，
<select id="findOrdersUserResultMap" resultMap="ordersUserResultMap">
select * from demo d,demo1 d1 where demo.id = demo1.id
</select>
6、方法二直接返回map集合，
<select id="findOrdersUserResultMap" resultMap="ordersUserResultMap">
select d.id as id,a.name as name,d.age as age,d.password as word ,d1.name as name1 from demo d,demo1 d1 where demo.id = demo1.id
</select>
7、此方法直接将两个对象的属性直接封装在map集合里面，用的时候直接去，相当于在entity层创建dto层；当然，也可以在entity创建dto层，返回dto实体对象；
