JAVA动态代理（proxy）实现和源码剖析

JDK动态代理实例

（1）动态代理首先提供一个调度处理器接口（Invocationhandler），该接口实例封装了我们要代理的对象实例的数据。

    public class TranceHander implements InvocationHandler{  
        private Object tObject;  
        public TranceHander(Object t){  
            tObject=t;  
        }  
        @Override  
        public Object invoke(Object proxy, Method method, Object[] args)  
                throws Throwable {  
            // TODO Auto-generated method stub  
            System.out.println("被代理对象："+tObject);  
            System.out.println("方法："+method.getName());  
            return method.invoke(tObject,args);//方法反射  
        }  
    }  

（2）使用Proxy类的newProxyInstance方法创建代理对象或getProxyClass方法获得代理类Class。

测试mian方法中，写了一个代理类，从1-1000的整数数组中使用二分查找随机查找一个整数，实现对象比较和toString接口代理

    public class ProxyTest {  

        /** 
         * @param args 
         */  
        public static void main(String[] args) {  
            // TODO Auto-generated method stub  
            Object[] elements=new Object[1000];  
            for(int i=0;i1;//被代理对象  
                InvocationHandler handler=new TranceHander(value);//构建调度处理器  
                Object proxy=Proxy.newProxyInstance(null, new Class[]{Comparable.class}, handler);  
                elements[i]=proxy;  
            }  
            Integer key=new Random().nextInt(1000)+1;  
            int res=Arrays.binarySearch(elements, key);  
            if(res>=0){  
                System.out.println(elements[res].toString());  
            }  
            System.out.println("查找Key："+key);  
        }  
    }  

JDK源码实现原理分析

（1）代理对象生成：

    Object proxy=Proxy.newProxyInstance(null, new Class[]{Comparable.class}, handler);  

（2）查看Proxy类的newProxyInstance方法
从生成对象方法中，我们看到三个关键的地方：

Class cl = getProxyClass0(loader, interfaces);//得到代理类
final Constructor cons = cl.getConstructor(constructorParams);   
newInstance(cons, ih);//将InvocationHandler h传入代理对象中

    public static Object newProxyInstance(ClassLoader loader,  
                                          Class[] interfaces,  
                                          InvocationHandler h)  
        throws IllegalArgumentException  
    {  
        if (h == null) {  
            throw new NullPointerException();  
        }  

        final SecurityManager sm = System.getSecurityManager();  
        if (sm != null) {  
            checkProxyAccess(Reflection.getCallerClass(), loader, interfaces);  
        }  

        /* 
         * Look up or generate the designated proxy class. 
         */  
        Class cl = getProxyClass0(loader, interfaces);  

        /* 
         * Invoke its constructor with the designated invocation handler. 
         */  
        try {  
            final Constructor cons = cl.getConstructor(constructorParams);  
            final InvocationHandler ih = h;  
            if (sm != null && ProxyAccessHelper.needsNewInstanceCheck(cl)) {  
                // create proxy instance with doPrivilege as the proxy class may  
                // implement non-public interfaces that requires a special permission  
                return AccessController.doPrivileged(new PrivilegedAction