设计模式读书笔记-1代理模式Proxy(2)

最新推荐文章于 2025-11-09 17:55:06 发布

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本文探讨了如何将虚拟代理与状态模式结合使用来实现Java动态代理，并提供了两个实现示例。文章还介绍了Java动态代理的实现机制及扩展，通过实例深入分析了动态代理的应用。

[b]1.虚拟代理与状态模式相结合[/b]
State


package headfirst.proxy.virtualproxy;
import java.awt.Component;
import java.awt.Graphics;
public interface State {
	public int getIconWidth();
	public int getIconHeight();
	public void paintIcon(final Component c, Graphics  g, int x,  int y);
}

ImageNotLoadedState


package headfirst.proxy.virtualproxy;

import java.awt.Component;
import java.awt.Graphics;
import java.net.URL;

import javax.swing.ImageIcon;

public class ImageNotLoadedState implements State {

	private URL imageURL;
	private ImageIcon imageIcon;
	public ImageIcon getImageIcon() {
		return imageIcon;
	}

	public void setImageIcon(ImageIcon imageIcon) {
		this.imageIcon = imageIcon;
	}

	private boolean retrieving = false;
	private Thread retrievalThread;

	private ImageProxyWithState imageProxy;

	public ImageNotLoadedState(ImageProxyWithState imageProxy, URL url) {
		this.imageProxy = imageProxy;
		this.imageURL = url;
	}

	public int getIconWidth() {
		return 800;
	}

	public int getIconHeight() {
		return 600;
	}

	public void paintIcon(final Component c, Graphics g, int x, int y) {
		g.drawString("Loading CD cover, please wait...", x+300, y+190);
		if (!retrieving) {
			retrieving = true;

			retrievalThread = new Thread(new Runnable() {
				public void run() {
					try {
						imageIcon = new ImageIcon(imageURL, "CD Cover");
						imageProxy.setCurrentState(imageProxy.getImageLoadedState());
						((ImageLoadedState)imageProxy.getImageLoadedState()).setImageIcon(
								((ImageNotLoadedState)imageProxy.getImageNotLoadedState()).getImageIcon());
						c.repaint();
					} catch (Exception e) {
						e.printStackTrace();
					}
				}
			});
			retrievalThread.start();
		}
	}

}

ImageLoadedState


package headfirst.proxy.virtualproxy;

import java.awt.Component;
import java.awt.Graphics;

import javax.swing.ImageIcon;

public class ImageLoadedState implements State {

	private ImageIcon imageIcon;

	public ImageIcon getImageIcon() {
		return imageIcon;
	}

	public void setImageIcon(ImageIcon imageIcon) {
		this.imageIcon = imageIcon;
	}

	public int getIconWidth() {
		return imageIcon.getIconWidth();
	}

	public int getIconHeight() {
		return imageIcon.getIconHeight();
	}

	public void paintIcon(Component c, Graphics g, int x, int y) {
		imageIcon.paintIcon(c, g, x, y);
	}

}

ImageProxyWithState


package headfirst.proxy.virtualproxy;

import java.awt.Component;
import java.awt.Graphics;
import java.net.URL;

import javax.swing.Icon;

class ImageProxyWithState implements Icon {
    State currentState; 
	State imageNotLoadedState;
	State imageLoadedState;

	public ImageProxyWithState(URL url) { 
		imageNotLoadedState = new ImageNotLoadedState(this, url);
		imageLoadedState = new ImageLoadedState();
		currentState = imageNotLoadedState;
	}

	public State getCurrentState() {
		return currentState;
	}

	public void setCurrentState(State currentState) {
		this.currentState = currentState;
	}

	public State getImageNotLoadedState() {
		return imageNotLoadedState;
	}

	public void setImageNotLoadedState(State imageNotLoadedState) {
		this.imageNotLoadedState = imageNotLoadedState;
	}

	public State getImageLoadedState() {
		return imageLoadedState;
	}

	public void setImageLoadedState(State imageLoadedState) {
		this.imageLoadedState = imageLoadedState;
	}

	public int getIconWidth() {
		return currentState.getIconWidth();
	}

	public int getIconHeight() {
		return currentState.getIconHeight();
	}

	public void paintIcon(final Component c, Graphics  g, int x,  int y) {
		currentState.paintIcon(c, g, x, y);
	}
}

[b]2.Java动态代理实现机制及扩展[/b]
[url]http://www.ibm.com/developerworks/cn/java/j-lo-proxy1/[/url]
[url]http://www.ibm.com/developerworks/cn/java/j-lo-proxy2/[/url]