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动态代理
public interface HelloWorld
{
void sayHello(String name);
}
public HelloWorldImpl implements HelloWorld
{
@Override
public void sayHello(String name)
{
System.out.println("Hello " + name);
}
}
实现java的动态代理接口
public class CustomInvocationHandler implements InvocationHandler
{
private Object target;
public CustomInvocationHandler(Object target)
{
this.target = target;
}
@Override
public Object invoke(Object proxy,Method method,Object[] args)throw Throwable
{
Object retVal = method.invoke(target,args);
return retVal;
}
}
使用代理类
public class ProxyTest
{
public static void main(String[] args) throws Exception
{
InvocationHandler handler = new CustomInvocationHandler(new HelloWorldImpl())；
HelloWorld proxy = (HelloWorld)Proxy.newProxyInstance(
ProxyTest.class.getClassLoder(),new Class[]{HelloWorld.class},handler);
proxy.sayHello("你好")；
)
}
}
=====================================
public class Proxy
{
private static Map loaderToCache = new WeakHashMap();
private static Object pendingGenerationMarke = new Object();
private static Map proxyClass Collections.synchronizedMap(new WeakHashMap());
protected InvocationHandler h;
protected Proxy(InvocationHandler h)
{
this.h = h;
}
private Proxy(){}
public static Object newProxyInstance(ClassLoader loader,class<?> [] interface,InvocationHandler h)
{
if(h == null)
{
throw new NullPointerException();
}
Class cl = getProxyClass(loader,interface);
Constructor cons = cl.getConstructor(constructorParams); //constructorParams這個怎麽來的
cons.newInstance(new Object[]{h});
}
public getProxyClass
}
======================================动态代理总结================================
1 通过实现InvocationHandler接口创建自己的调用处理器
InvocationHandler handler = new InvocationHandlerImpl(...)
2 通过为Proxy类指定ClassLoader对象和一组interface创建动态代理类
Proxy.getProxyClass(classLoader,new Class[]{...});
3 通过反射机制获取动态代理类的构造函数，其参数类型是调用处理器接口类型
Constructor constructor = clazz.getConstructor(new Class[]{InvocationHandler.Class});
4 通过构造函数创建代理类实例，此时需要将调用处理器对象作为参数传入
Interfae Proxy = constructor.newInstance(new Object[](handler));
为了简化对象创建过程，Proxy类中的newInstance方法封装了2-4，只需要两步即可完成代理对象的创建
生成的ProxySubject 继承 Proxy 类 实现 Subject接口，实现的Subject的方法实际调用处理器的invoke方法
而invoke方法利用反射调用的是被代理对象的方法
(Object)method.invoke(proxied,args)
动态代理