之前说了由Employee找Department，这一节讲一讲由Department找Employee，显然前者是多对一的关系，而后者是一对多的关系。
Department的JavaBean：
private Integer id;
private String departmentName;
private List<Employee> employeeList; |
接口中的方法：
Department getDepByIdPlus(Integer id);
查询的SQL语句：
<select id="getDepByIdPlus" resultMap="Dep">
SELECT d.`id` did,d.`department_name` dep_name,e.`id` eid,e.`last_name` last_name,e.`email` email,e.`gender` gender
FROM tb_department d LEFT JOIN tb_employee e
ON d.`id`=e.`d_id`
WHERE d.`id`=2;
</select> |
接下来编写resultMap，
collection：定义关联集合类型的属性的封装规则
ofType：指定集合里面的元素类型
<resultMap id="Dep" type="com.figsprite.bean.Department">
<id property="id" column="did"/>
<result property="departmentName" column="dep_name"/>
<collection property="employeeList" ofType="com.figsprite.bean.Employee">
<id property="id" column="eid"/>
<result property="lastName" column="last_name"/>
<result property="gender" column="gender"/>
<result property="email" column="email"/>
</collection>
</resultMap> |
其实就是一个resultMap套着另外一个resultMap格式的collection
@Test
public void test2() throws IOException {
SqlSessionFactory sqlSessionFactory = getSqlSessionFactory();
SqlSession sqlOpenSession = sqlSessionFactory.openSession();
try {
DepartmentMapper departmentMapper = sqlOpenSession.getMapper(DepartmentMapper.class);
Department department = departmentMapper.getDepByIdPlus(1);
for (Employee e : department.getEmployeeList()) {
System.out.println(e);
}
} finally {
sqlOpenSession.close();
}
} |