This article mainly introduces the relevant information of Javaproxy mode in detail, which has certain reference value. Interested friends can refer to it
The proxy mode is ours One of the more commonly used design patterns. The new idea is to insert a proxy object between the actual object and the caller in order to provide additional processing or different operations. These additional operations usually require communication with the actual object. The roles generally involved in the proxy pattern are:
Abstract role: declare the common interface of the real object and the proxy object;
Proxy role: The proxy object role contains a reference to the real object internally, so that the real object can be manipulated. At the same time, the proxy object provides the same interface as the real object so that it can replace the real object at any time. At the same time, the proxy object can add other operations when performing operations on the real object, which is equivalent to encapsulating the real object.
Real role: The real object represented by the proxy role is the object we ultimately want to reference.
The following takes Sending a message as an example to illustrate the basic implementation of a simple proxy mode:
First clarify the purpose: there is a message that needs To send this message, define the corresponding interface MessageHandler according to this purpose. Additional operations required: Suppose we need to verify that the length of the message cannot exceed the specified length and cannot be empty, and we need to count the number of times relevant information is sent. If the number exceeds the specified number, we need to output an alert. We implement this additional operation through the proxy pattern. The following is the corresponding class diagram and sample code.
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//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
Dynamic Agent
lang.reflect package, which generally involves the following two classes:
Protected Proxy(InvocationHandler h):
Constructor is estimated to be used to assign a value to the internal h. Static Class getProxyClass (ClassLoader loader, Class[] interfaces): Get a proxy class, where loader is the class loader and interfaces is an array of all interfaces owned by the real class.
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 !
以上例子中,通过调用Proxy.newProxyInstance方法创建动态代理对象,该方法需要传入一个 类加载器、一组希望代理实现的接口列表、InvocationHandler 接口的一个具体实现。动态代理可以将所有调用重定向到调用处理器,通常我们会向该处理器传递一个时间对象的引用。invoke()方法中传递进来了代理对象,当你需要区分请求来源时这是非常有用的,例如你可以通过判断传入的方法名屏蔽掉某些方法的执行!动态代理机制并不是会很频繁使用的方法,它通常用来解决一些特定情况下的问题,因此不要盲目的为了使用而使用,要根据自己的实际需求来决定!
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