Proxy 代理模式学习笔记

1. 意图:
为其他对象提供一种代理以控制对这个对象的访问

2. 别名:
surrogate替身

3. 动机
按需创建, 替代对象

4. 适用性
* 远程代理
* 虚代理
* 保护代理
* 智能指引

5. 结构




6. 实例

Java代码
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();  
 
    }  
 
} 

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中的动态代理

Java代码
/** 
*  
*/ 
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();  
    }  
 
} 

/**
*
*/
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();
    }

}