[Spring] 템플릿과 콜백 예제

UserDaoTest.java (테스트용 클라이언트 Class)

package springbook.user;

@RunWith(SpringJUnit4ClassRunner.class)

@ContextConfiguration(locations = "/applicationContext.xml")

public class UserDaoTest {

/*

* ApplicationContext 객체를 사용하여 getBean을 이용하여 UserDao에 DI를 주입 할수도 있지만

* Autowired 를 통하여 바로 UserDao에 DI를 주입하는 방법을 통해 

* ApplicationContext 객체를 사용하지 않는 방법을 택했다.

* 

* @Autowired 

* private ApplicationContext context;

*/

@Autowired

private UserDao dao;

private User user1;

private User user2;

private User user3;

@Before

public void setUp() {

/*

* Configuration File인 daoFactory.class 에서 userDao 라는 빈을 가지고 오고 그

* userDao 라는 빈은 UserDao Object를 반환한다.

*/

// this.dao = context.getBean("userDao", UserDao.class);

user1 = new User("SexyGuy", "김성민", "springman1");

user2 = new User("delay", "류민기", "springman2");

user3 = new User("postpone", "송준화", "springman3");

}

public static void main(String[] args) {

JUnitCore.main("springbook.user.UserDaoTest");

}

@Test

public void addAndGet() throws ClassNotFoundException, SQLException {

dao.deleteAll();

assertThat(dao.getCount(), is(0));

dao.deleteAll();

assertThat(dao.getCount(), is(0));

dao.add(user1);

dao.add(user2);

dao.add(user3);

assertThat(dao.getCount(), is(3));

User userget1 = dao.get(user1.getId());

assertThat(userget1.getName(), is(user1.getName()));

assertThat(userget1.getPassword(), is(user1.getPassword()));

User userget2 = dao.get(user2.getId());

assertThat(userget2.getName(), is(user2.getName()));

assertThat(userget2.getPassword(), is(user2.getPassword()));

User userget3 = dao.get(user3.getId());

assertThat(userget3.getName(), is(user3.getName()));

assertThat(userget3.getPassword(), is(user3.getPassword()));

}

@Test(expected = EmptyResultDataAccessException.class)

public void getUserFaiure() throws SQLException, ClassNotFoundException {

dao.deleteAll();

assertThat(dao.getCount(), is(0));

dao.get("unknown_id");

}

}

applicationContext.xml (@Configuration과 @Bean 환경설정 xml)

<beans>

<bean id="userDao" class="springbook.user.dao.UserDao">

<property name="dataSource" ref="dataSource" />

</bean>

<bean id="dataSource" class="org.springframework.jdbc.datasource.SimpleDriverDataSource">

<property name="driverClass" value="oracle.jdbc.OracleDriver" />

<property name="url" value="jdbc:oracle:thin:@localhost:1521:orcl" />

<property name="username" value="scott" />

<property name="password" value="tiger" />

</bean>

</beans>

UserDao.java (의존성 주입을 당할 자바 빈 Class)

public class UserDao {

private DataSource dataSource;

private JdbcContext jdbcContext;

public void setDataSource(DataSource dataSource) {

this.jdbcContext = new JdbcContext();

this.jdbcContext.setDataSource(dataSource);

this.dataSource = dataSource;

}

public void deleteAll() throws SQLException  {

this.jdbcContext.executeSql("delete from users");

}

...

}

JdbcContext.java (템플릿과 콜백 패턴을 써서 만든 Class)

public class JdbcContext {

private DataSource dataSource;

public void setDataSource(DataSource dataSource) {

this.dataSource = dataSource;

}

public void workWithStatementStrategy (StatementStrategy stmt) throws SQLException {

Connection c = null;

PreparedStatement ps = null;

try {

c = dataSource.getConnection();

ps = stmt.makePreparedStatement(c);

ps.executeUpdate();

} catch (SQLException e) {

throw e;

} finally {

if (ps != null) { try { ps.close(); } catch (SQLException e) {} }

if (c != null) { try { c.close(); } catch (SQLException e) {} }

}

}

public void executeSql(final String query) throws SQLException {

workWithStatementStrategy( new StatementStrategy() {

@Override

public PreparedStatement makePreparedStatement(Connection c) throws SQLException {

return c.prepareStatement(query);

}

}); 

}

}

StatementStrategy.java (전략 패턴을 써야 함으로 인한 Interface)

public interface StatementStrategy {

PreparedStatement makePreparedStatement(Connection c) throws SQLException;

}