java 简单的动态代理例子

package util;
import java.lang.reflect.InvocationHandler;
import java.lang.reflect.Proxy;
import java.lang.reflect.Method;
//抽象角色：java动态代理的实现目前只支持接口，不支持抽象类
interface BusinessFoo
{
void foo();
}
interface BusinessBar
{
String bar(String message);
}
//真实角色：真正实现业务逻辑方法
class BusinessFooImpl implements BusinessFoo
{
public void foo()
{
System.out.println("BusinessFooImpl.foo()");
}
}
class BusinessBarImpl implements BusinessBar
{
public String bar(String message)
{
System.out.println("BusinessBarImpl.bar()");
return message;
}
}
//动态角色：动态生成代理类
class BusinessImplProxy implements InvocationHandler
{
private Object obj;
BusinessImplProxy() {
}
BusinessImplProxy(Object obj) {
this.obj = obj;
}
public Object invoke(Object proxy,Method method,Object[] args) throws Throwable
{
Object result = null;
doBefore();
result = method.invoke(obj,args);
doAfter();
return result;
}
public void doBefore(){
System.out.println("do something before Business Logic");
}
public void doAfter(){
System.out.println("do something after Business Logic");
}
public static Object factory(Object obj)
{
Class cls = obj.getClass();
return Proxy.newProxyInstance(cls.getClassLoader(),cls.getInterfaces(),new BusinessImplProxy(obj));
}
}
//测试类
public class DynamicProxy
{
public static void main(String[] args) throws Throwable
{
BusinessFooImpl bfoo = new BusinessFooImpl();
BusinessFoo bf = (BusinessFoo)BusinessImplProxy.factory(bfoo);
bf.foo();
System.out.println();

BusinessBarImpl bbar = new BusinessBarImpl();
BusinessBar bb = (BusinessBar)BusinessImplProxy.factory(bbar);
String message = bb.bar("Hello,World");
System.out.println(message);
}
}