POJO中的属性可能会是一个对象,我们可以使用联合查询，并以级联属性的方式封装对象.使用association标签定义对象的封装规则
public class Department { private Integer id ; private String departmentName ; // 省略 get/set方法 } public class Employee { private Integer id ; private String lastName; private String email ; private String gender ; private Department dept ; // 省略 get/set方法 }使用级联的方式:
<select id="getEmployeeAndDept" resultMap="myEmpAndDept" > SELECT e.id eid, e.last_name, e.email,e.gender ,d.id did, d.dept_name FROM tbl_employee e , tbl_dept d WHERE e.d_id = d.id AND e.id = #{id} </select> <resultMap type="com.atguigu.mybatis.beans.Employee" id="myEmpAndDept"> <id column="eid" property="id"/> <result column="last_name" property="lastName"/> <result column="email" property="email"/> <result column="gender" property="gender"/> <!-- 级联的方式 --> <result column="did" property="dept.id"/> <result column="dept_name" property="dept.departmentName"/> </resultMap>Association的用法
<resultMap type="com.atguigu.mybatis.beans.Employee" id="myEmpAndDept"> <id column="eid" property="id"/> <result column="last_name" property="lastName"/> <result column="email" property="email"/> <result column="gender" property="gender"/> <association property="dept" javaType="com.atguigu.mybatis.beans.Department"> <id column="did" property="id"/> <result column="dept_name" property="departmentName"/> </association> </resultMap>