1. 意圖:
為其他對象提供一種代理以控制對這個對象的訪問

2. 別名:
surrogate替身

3. 動機
按需創建, 替代對象

4. 適用性
* 遠程代理
* 虛代理
* 保護代理
* 智能指引

5. 結構


6. 實例

    package net.yeah.fanyamin.pattern.proxy;

/**
 * @author walter
 */
interface Greet {
    void sayHello(String name);
    void goodBye();
}

class GreetImpl implements Greet {
    public void sayHello(String name) {
        System.out.println("Hello " + name);
    }
    public void goodBye() {
        System.out.println("Good bye.");
    }
}

public class SimpleProxy implements Greet {
    private Greet greet = null;
    
    SimpleProxy(Greet greet) {
        this.greet = greet;
    }
    
    public void sayHello(String name) {
        System.out.println("--before method sayHello");
        greet.sayHello(name);
        System.out.println("--after method sayHello");
    }
    
    public void goodBye() {
        System.out.println("--before method goodBye");
        greet.goodBye();
        System.out.println("--after method goodBye");
    }
    /**
     * @param args
     */
    public static void main(String[] args) {
        Greet greet = new SimpleProxy(new GreetImpl());
        greet.sayHello("walter");
        greet.goodBye();

    }

}

  

?利用JDK中的動態代理

    /**
 * 
 */
package net.yeah.fanyamin.pattern.proxy;

import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;

/**
 * @author walter
 */
public class DebugProxy implements java.lang.reflect.InvocationHandler {

    private Object obj;

    public static Object newInstance(Object obj) {
        return java.lang.reflect.Proxy.newProxyInstance(obj.getClass().getClassLoader(),
                                                        obj.getClass().getInterfaces(), new DebugProxy(obj));
    }

    private DebugProxy(Object obj) {
        this.obj = obj;
    }

    public Object invoke(Object proxy, Method m, Object[] args) throws Throwable {
        Object result;
        try {
            System.out.println("--before method " + m.getName());
            result = m.invoke(obj, args);
        } catch (InvocationTargetException e) {
            throw e.getTargetException();
        } catch (Exception e) {
            throw new RuntimeException("unexpected invocation exception: " + e.getMessage());
        } finally {
            System.out.println("--after method " + m.getName());
        }
        return result;
    }

    /**
     * @param args
     */
    public static void main(String[] args) {
        Greet greet = (Greet) DebugProxy.newInstance(new GreetImpl());
        greet.sayHello("walter");
        greet.goodBye();
    }

}

  

?

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Proxy 代理模式筆記