Java代理模式详细解析

//接口定义  
public interface MessageHandler {  
public void sendMessage(String msg);  
}  
//通过Email方式发送消息的实现类  
public class EmailMessage implements MessageHandler {  
@Override  
public void sendMessage(String msg) {  
// TODO Auto-generated method stub  
System.out.println(msg+" send!!");  
}  
}  
//消息处理的代理类  
public class MessageProxy implements MessageHandler {  
private static int count;  
private MessageHandler emailMsg;  
@Override  
public void sendMessage(String msg) {  
// TODO Auto-generated method stub  
if(checkMessage(msg))  
{  
if(emailMsg==null) emailMsg=new EmailMessage();  
count++;  
emailMsg.sendMessage(msg);  
System.out.println("Message sent:"+count);  
}  
}  
private boolean checkMessage(String msg) {  
return msg != null && msg.length() > 10;  
}  
}  
//调用类  
public class MainClass {  
private static void runProxy(MessageHandler handler)  
{  
handler.sendMessage("message for test");  
}  
/** 
 * @param args 
 */  
public static void main(String[] args) {  
// TODO Auto-generated method stub  
runProxy(new EmailMessage());  
System.out.println("++++++++++++++++Pjroxy++++++++++++++++++");  
runProxy(new MessageProxy());  
}  
}  
//输出  
message for test send!!  
++++++++++++++++Pjroxy++++++++++++++++++  
message for test send!!  
Message sent:1 

public class SmsMessage implements MessageHandler {  
@Override  
public void sendMessage(String msg) {  
// TODO Auto-generated method stub  
System.out.println("SMS Message :" + msg+" sent !");  
}  
}  
//动态代理类  
import java.lang.reflect.InvocationHandler;  
import java.lang.reflect.Method;  
public class DynamicMessageProxy implements InvocationHandler {  
private static int count;  
private MessageHandler msgHandler;  
public DynamicMessageProxy(MessageHandler handler) {  
msgHandler = handler;  
}  
@Override  
public Object invoke(Object proxy, Method method, Object[] args)  
throws Throwable {  
// TODO Auto-generated method stub  
System.out.println("++++++++=============+++++++++");  
System.out.println("proxy:" + proxy.getClass());  
System.out.println("method:" + method);  
System.out.println("++++++++=============+++++++++");  
if (args != null && args.length == 1 && checkMessage((String) args[0])) {  
count++;  
System.out.println("Message sent:" + count);  
return method.invoke(msgHandler, args);  
}  
return null;  
}  
private boolean checkMessage(String msg) {  
return msg != null && msg.length() > 10;  
}  
}  
//下面是调用  
import java.lang.reflect.Proxy;  
public class MainClass {  
private static void runProxy(MessageHandler handler) {  
handler.sendMessage("message for test");  
}  
/** 
 * @param args 
 */  
public static void main(String[] args) {  
// TODO Auto-generated method stub  
// runProxy(new EmailMessage());  
// System.out.println("++++++++++++++++Proxy++++++++++++++++++");  
// runProxy(new MessageProxy());  
MessageHandler handler = new EmailMessage();  
runProxy(handler);  
MessageHandler proxy = (MessageHandler) Proxy.newProxyInstance(  
MessageHandler.class.getClassLoader(),  
new Class[] { MessageHandler.class }, new DynamicMessageProxy(  
handler));  
runProxy(proxy);  
System.out.println("++++++++++++++++++++++++++++++++++");  
// 短信方式  
handler = new SmsMessage();  
runProxy(handler);  
proxy = (MessageHandler) Proxy.newProxyInstance(MessageHandler.class  
.getClassLoader(), new Class[] { MessageHandler.class },  
new DynamicMessageProxy(handler));  
runProxy(proxy);  
}  
}  
//下面为以上方法的输出：  
message for test send!!  
++++++++=============+++++++++  
proxy:class $Proxy0  
method:public abstract void MessageHandler.sendMessage(java.lang.String)  
++++++++=============+++++++++  
Message sent:1  
message for test send!!  
++++++++++++++++++++++++++++++++++  
SMS Message :message for test sent !  
++++++++=============+++++++++  
proxy:class $Proxy0  
method:public abstract void MessageHandler.sendMessage(java.lang.String)  
++++++++=============+++++++++  
Message sent:2  
SMS Message :message for test sent !