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。

心跳反映的代码：

*** * 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()*/@Overridepublic String toString() {return new SimpleDateFormat("yyyy-MM-dd HH:mm:ss").format(new Date())+"\t维持连接包";}}

客户端的代码：

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();} }}}}

服务短的代码：

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());}}}