JAVA实现长连接(含心跳检测Demo)

实现原理：
       长连接的维持，是要客户端程序，定时向服务端程序，发送一个维持连接包的。
       如果，长时间未发送维持连接包，服务端程序将断开连接。

客户端：
       Client通过持有Socket的对象，可以随时（使用sendObject方法）发送Massage Object(消息)给服务端。
       如果keepAliveDelay毫秒（程序中是2秒）内未发送任何数据，则自动发送一个KeepAlive Object(心跳)给服务端，用于维持连接。
       由于，我们向服务端，可以发送很多不同的消息对象，服务端也可以返回不同的对象。所以，对于返回对象的处理，要编写具体的ObjectAction实现类进行处理。通过Client.addActionMap方法进行添加。这样，程序会回调处理。

服务端：
        由于客户端会定时（keepAliveDelay毫秒）发送维持连接的信息过来，所以，服务端要有一个检测机制。
        即当服务端receiveTimeDelay毫秒（程序中是3秒）内未接收任何数据，则自动断开与客户端的连接。
         ActionMapping的原理与客户端相似（相同）。

通过添加相应的ObjectAction实现类，可以实现不同对象的响应、应答过程。

Demo:

package socket.keepalive.test;

import java.io.Serializable;
import java.text.SimpleDateFormat;
import java.util.Date;

/**
 *
 * 维持连接的消息对象（心跳对象）
 */
public class KeepAlive implements Serializable{

 private static final long serialVersionUID = -2813120366138988480L;

 /* 覆盖该方法，仅用于测试使用。
 * @see java.lang.Object#toString()
 */
 @Override
 public String toString() {
 return new SimpleDateFormat("yyyy-MM-dd HH:mm:ss").format(new Date())+"\t维持连接包";
 }

}

package socket.keepalive.test;

import java.io.IOException;
import java.io.InputStream;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.net.Socket;
import java.net.UnknownHostException;
import java.util.Collections;
import java.util.concurrent.ConcurrentHashMap;

/**
 * C/S架构的客户端对象，持有该对象，可以随时向服务端发送消息。
 * <p>
 * 创建时间：2010-7-18 上午12:17:25
 * @author HouLei
 * @since 1.0
 */
public class Client {

 /**
 * 处理服务端发回的对象，可实现该接口。
 */
 public static interface ObjectAction{
 void doAction(Object obj,Client client);
 }

 public static final class DefaultObjectAction implements ObjectAction{
 public void doAction(Object obj,Client client) {
  System.out.println("处理：\t"+obj.toString());
 }
 }

 public static void main(String[] args) throws UnknownHostException, IOException {
 String serverIp = "127.0.0.1";
 int port = 65432;
 Client client = new Client(serverIp,port);
 client.start();
 }

 private String serverIp;
 private int port;
 private Socket socket;
 private boolean running=false; //连接状态

 private long lastSendTime; //最后一次发送数据的时间

 //用于保存接收消息对象类型及该类型消息处理的对象
 private ConcurrentHashMap<Class, ObjectAction> actionMapping = new ConcurrentHashMap<Class,ObjectAction>();

 public Client(String serverIp, int port) {
 this.serverIp=serverIp;
 this.port=port;
 }

 public void start() throws UnknownHostException, IOException {
 if(running)return;
 socket = new Socket(serverIp,port);
 System.out.println("本地端口："+socket.getLocalPort());
 lastSendTime=System.currentTimeMillis();
 running=true;
 new Thread(new KeepAliveWatchDog()).start(); //保持长连接的线程，每隔2秒项服务器发一个一个保持连接的心跳消息
 new Thread(new ReceiveWatchDog()).start();  //接受消息的线程，处理消息
 }

 public void stop(){
 if(running)running=false;
 }

 /**
 * 添加接收对象的处理对象。
 * @param cls 待处理的对象，其所属的类。
 * @param action 处理过程对象。
 */
 public void addActionMap(Class<Object> cls,ObjectAction action){
 actionMapping.put(cls, action);
 }

 public void sendObject(Object obj) throws IOException {
 ObjectOutputStream oos = new ObjectOutputStream(socket.getOutputStream());
 oos.writeObject(obj);
 System.out.println("发送：\t"+obj);
 oos.flush();
 }

 class KeepAliveWatchDog implements Runnable{
 long checkDelay = 10;
 long keepAliveDelay = 2000;
 public void run() {
  while(running){
  if(System.currentTimeMillis()-lastSendTime>keepAliveDelay){
   try {
   Client.this.sendObject(new KeepAlive());
   } catch (IOException e) {
   e.printStackTrace();
   Client.this.stop();
   }
   lastSendTime = System.currentTimeMillis();
  }else{
   try {
   Thread.sleep(checkDelay);
   } catch (InterruptedException e) {
   e.printStackTrace();
   Client.this.stop();
   }
  }
  }
 }
 }

 class ReceiveWatchDog implements Runnable{
 public void run() {
  while(running){
  try {
   InputStream in = socket.getInputStream();
   if(in.available()>0){
   ObjectInputStream ois = new ObjectInputStream(in);
   Object obj = ois.readObject();
   System.out.println("接收：\t"+obj);
   ObjectAction oa = actionMapping.get(obj.getClass());
   oa = oa==null?new DefaultObjectAction():oa;
   oa.doAction(obj, Client.this);
   }else{
   Thread.sleep(10);
   }
  } catch (Exception e) {
   e.printStackTrace();
   Client.this.stop();
  }
  }
 }
 }

}

package socket.keepalive.test;

import java.io.IOException;
import java.io.InputStream;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.net.ServerSocket;
import java.net.Socket;
import java.util.concurrent.ConcurrentHashMap;

/**
 * C/S架构的服务端对象。
 * <p>
 * 创建时间：2010-7-18 上午12:17:37
 * @author HouLei
 * @since 1.0
 */
public class Server {

 /**
 * 要处理客户端发来的对象，并返回一个对象，可实现该接口。
 */
 public interface ObjectAction{
 Object doAction(Object rev, Server server);
 }

 public static final class DefaultObjectAction implements ObjectAction{
 public Object doAction(Object rev,Server server) {
  System.out.println("处理并返回："+rev);
  return rev;
 }
 }

 public static void main(String[] args) {
 int port = 65432;
 Server server = new Server(port);
 server.start();
 }

 private int port;
 private volatile boolean running=false;
 private long receiveTimeDelay=3000;
 private ConcurrentHashMap<Class, ObjectAction> actionMapping = new ConcurrentHashMap<Class,ObjectAction>();
 private Thread connWatchDog;

 public Server(int port) {
 this.port = port;
 }

 public void start(){
 if(running)return;
 running=true;
 connWatchDog = new Thread(new ConnWatchDog());
 connWatchDog.start();
 }

 @SuppressWarnings("deprecation")
 public void stop(){
 if(running)running=false;
 if(connWatchDog!=null)connWatchDog.stop();
 }

 public void addActionMap(Class<Object> cls,ObjectAction action){
 actionMapping.put(cls, action);
 }

 class ConnWatchDog implements Runnable{
 public void run(){
  try {
  ServerSocket ss = new ServerSocket(port,5);
  while(running){
   Socket s = ss.accept();
   new Thread(new SocketAction(s)).start();
  }
  } catch (IOException e) {
  e.printStackTrace();
  Server.this.stop();
  }

 }
 }

 class SocketAction implements Runnable{
 Socket s;
 boolean run=true;
 long lastReceiveTime = System.currentTimeMillis();
 public SocketAction(Socket s) {
  this.s = s;
 }
 public void run() {
  while(running && run){
  if(System.currentTimeMillis()-lastReceiveTime>receiveTimeDelay){
   overThis();
  }else{
   try {
   InputStream in = s.getInputStream();
   if(in.available()>0){
    ObjectInputStream ois = new ObjectInputStream(in);
    Object obj = ois.readObject();
    lastReceiveTime = System.currentTimeMillis();
    System.out.println("接收：\t"+obj);
    ObjectAction oa = actionMapping.get(obj.getClass());
    oa = oa==null?new DefaultObjectAction():oa;
    Object out = oa.doAction(obj,Server.this);
    if(out!=null){
    ObjectOutputStream oos = new ObjectOutputStream(s.getOutputStream());
    oos.writeObject(out);
    oos.flush();
    }
   }else{
    Thread.sleep(10);
   }
   } catch (Exception e) {
   e.printStackTrace();
   overThis();
   }
  }
  }
 }

 private void overThis() {
  if(run)run=false;
  if(s!=null){
  try {
   s.close();
  } catch (IOException e) {
   e.printStackTrace();
  }
  }
  System.out.println("关闭："+s.getRemoteSocketAddress());
 }

 }

}

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