그냥 그런게 있구나 하고 사용했는데
문뜩 알아보자 해서
http://devyongsik.tistory.com/294
요 포스팅을 봤거든요.
이제야 Class.forName, static 키워드, SPI에 대해 조금이나마 이해가 가네요.
확실하게 이해해보자 해서 실제 api declaration 보면서 따라가봤는데....
아직은 너무 어렵네요....
그래도 뭔가 원리를 깨우친 느낌!
아래는 제가 포스팅 보고 따라해본 예제입니다.
//Test.java - 클라이언트
//================================================================
package com.test;
public class Test {
public static void main(String[] args) throws ClassNotFoundException {
Class.forName("com.test.MyDriver");
Connection connection = DriverManager.getConnection();
}
}
/*출력 결과
Driver 등록
MyDriver's Connection return
*/
//================================================================
//Driver.java - JAVA에서 제공하는 인터페이스(java.sql)
//================================================================
package com.test;
public interface Driver {
Connection getConnection();
}
//================================================================
//Connection.java - JAVA에서 제공하는 인터페이스(java.sql)
//================================================================
package com.test;
public interface Connection {
}
//================================================================
//DriverManager.java - JAVA에서 제공하는 드라이버 매니저 클래스(java.sql)
//================================================================
package com.test;
import java.util.Map;
import java.util.concurrent.ConcurrentHashMap;
public class DriverManager {
private DriverManager() {}
private static final Map<String,Driver> drivers = new ConcurrentHashMap<String,Driver>();
public static final String DEFAULT_DRIVER_NAME = "default";
public static void registerDefaultPrivider(Driver d) {
System.out.println("Driver 등록");
registerDriver(DEFAULT_DRIVER_NAME, d);
}
public static void registerDriver(String name, Driver d) {
drivers.put(name,d);
}
public static Connection getConnection() {
return getConnection(DEFAULT_DRIVER_NAME);
}
public static Connection getConnection(String name) {
Driver d = drivers.get(name);
if(d==null)
throw new IllegalArgumentException();
return d.getConnection();
}
}
//================================================================
//MyDriver.java - 드라이버 밴더가 제공하는 클래스(ex: oracle.jdbc.driver.OracleDriver)
//================================================================
package com.test;
public class MyDriver implements Driver {
private static Driver defaultDriver;
static {
defaultDriver = new MyDriver();
com.test.DriverManager.registerDefaultPrivider(defaultDriver);
}
@Override
public Connection getConnection() {
System.out.println("MyDriver's Connection return");
return null;
}
}
//================================================================
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