設計模式（十）代理模式

代理：只需要對象進行相關的操作，對象操作的前後的處理的行爲人，即是代理。

代碼之靜態代理：

球員相關工作的接口：

public interface PlayerInterface {
	//踢球，球員本身的技能
	public void playFootBall();
	//下面爲經紀人(代理的工作)
	public void chooseFootBallTeam();
	public void getAdvertisement();
}

球員類實現其接口：

public class FootBallPlayer implements PlayerInterface{

	@Override
	public void playFootBall() {
		System.out.println("馳騁足壇");
	}

	@Override
	public void chooseFootBallTeam() {
		System.out.println("選擇偉大的俱樂部發展");
	}

	@Override
	public void getAdvertisement() {
		System.out.println("代言廣告");
	}
}

球員經紀人(代理)類實現接口：

public class PlayerProxy implements PlayerInterface{
	
	public PlayerProxy(PlayerInterface playerInterface) {
		super();
		this.playerInterface = playerInterface;
	}

	private PlayerInterface playerInterface;
	
	@Override
	public void playFootBall() {
		playerInterface.playFootBall();
	}

	@Override
	public void chooseFootBallTeam() {
		System.out.println("幫助球員選擇偉大的俱樂部發展");
	}

	@Override
	public void getAdvertisement() {
		System.out.println("幫助球員承接廣告");
	}
}

測試代碼：

public class Test {
	public static void main(String[] args) {
		PlayerInterface footBallPlayer = new FootBallPlayer();
		PlayerInterface playerProxy = new PlayerProxy(footBallPlayer);
		playerProxy.playFootBall();
		playerProxy.chooseFootBallTeam();
		playerProxy.getAdvertisement();
	}
}

輸出內容如下：

馳騁足壇
幫助球員選擇偉大的俱樂部發展
幫助球員承接廣告

代碼之動態代理：實現InvocationHandler接口

public class PlayerHandler implements InvocationHandler {

	private PlayerInterface playerInterface;
	
	public PlayerHandler(PlayerInterface playerInterface) {
		super();
		this.playerInterface = playerInterface;
	}

	@Override
	public Object invoke(Object proxy, Method method, Object[] args)
			throws Throwable {
		//進行方法的篩選
		if(method.getName().equals("playFootBall")){
			method.invoke(playerInterface, args);
		}
		return null;
	}

}

測試：

public static void main(String[] args) {
	PlayerInterface footBallPlayer = new FootBallPlayer();
	PlayerHandler handler = new PlayerHandler(footBallPlayer);
	PlayerInterface proxy = (PlayerInterface) Proxy.newProxyInstance(ClassLoader.getSystemClassLoader(), new Class[]{PlayerInterface.class}, handler);
	proxy.playFootBall();
	proxy.chooseFootBallTeam();
	proxy.getAdvertisement();
}

控制檯輸出：因爲只處理了playFootBall方法，故只打印了相關輸出

馳騁足壇