07. 조인하기 [Spring]
class A
private B b = new B();
class B
private A a = new A();
--> class A 와 class B가 끝없이 생성됨 (x : 생성시키면 안됨)
class A
private B b;
setB(B b);
class B
private A a;
setA(A a);
외부에서 만들어서 보내--> 상관없다
조인된 결과를 하나의 쿼리로 묶는 방법?
1. resultMap 사용! (객체 가져올때 씀)
--> 맵핑되어서 객체만들어 보내줌 (컬럼이 같으면 공통적으로 써도됨)
resultMap id 에는 Map을 붙인다
pk는 id column은 PK
result column 은 컬럼
property에 클래스 변수명 쓰고, 알리아스 지운다.
<association property="departments" javaType="DepartmentsVO">
property : EmployeesVO 에 있는 변수명
알리아스 : javaType
<코드>
<resultMap type="EmployeesVO" id="employeeMap">
<id column="EMPLOYEE_ID" property="employeeId"/>
<result column="FIRST_NAME" property="firstName"/>
<result column="LAST_NAME" property="lastName"/>
<result column="HIRE_DATE" property="hireDate"/>
<result column="SALARY" property="salary"/>
<result column="DEPARTMENT_ID" property="departmentId"/>
<association property="departments" javaType="DepartmentsVO">
<id column="DEPARTMENT_ID" property="departmentId"/>
<result column="DEPARTMENT_NAME" property="departmentName"/>
<result column="MANAGER_ID" property="managerId"/>
<result column="LOCATION_ID" property="locationId"/>
</association>
</resultMap>
<select id="getEmployeeByEmployeeId" resultMap="employeeMap" parameterType="string">
SELECT /* [indexDao.xml] [getEmployeeByEmployeeId] */
EMP.EMPLOYEE_ID
, EMP.FIRST_NAME
, EMP.LAST_NAME
, EMP.HIRE_DATE
, EMP.SALARY
, EMP.DEPARTMENT_ID
, DEPT.DEPARTMENT_NAME
, DEPT.MANAGER_ID
, DEPT.LOCATION_ID
FROM EMPLOYEES EMP
, DEPARTMENTS DEPT
WHERE EMP.DEPARTMENT_ID = DEPT.DEPARTMENT_ID
AND EMP.EMPLOYEE_ID = #{employeeId}
</select>
getEmployeeByEmployeeId 와 getDepartmentByEmployeesDepartmentId 묶기
<단건조인 1:1, 클래스 >
Row1 = Row1
--> association으로 처리한다.
(has one 관계)
<association property="departments" javaType="DepartmentsVO">
<id column="DEPARTMENT_ID" property="departmentId"/>
<result column="DEPARTMENT_NAME" property="departmentName"/>
<result column="MANAGER_ID" property="managerId"/>
<result column="LOCATION_ID" property="locationId"/>
</association>
<조인 1:다 리스트 has many>
<resultMap type="EmployeesVO" id="getEmployeeByEmployeeIdMap">
<id column="EMPLOYEE_ID" property="employeesId"/>
<result column="FIRST_NAME" property="firstName"/>
<result column="LAST_NAME" property="lastName"/>
<result column="HIRE_DATE" property="hireDate"/>
<result column="SALARY" property="salary"/>
<result column="DEPARTMENT_ID" property="departmentId"/>
<collection property="departments" resultMap="DepartmentsVO"/>
</resultMap>
<resultMap type="DepartmentsVO" id="DepartmentsVO">
<id column="DEPARTMENT_ID" property="departmentId"/>
<result column="DEPARTMENT_NAME" property="departmentName"/>
<result column="MANAGER_ID" property="managerId"/>
<result column="LOCATION_ID" property="locationId"/>
</resultMap>