socket长连接的维持

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：
通过持有Client对象，可以随时（使用sendObject方法）发送Object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对象给服务端，
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。

import java.io.Serializable;

import java.text.SimpleDateFormat;

import java.util.Date;

/**

 * 维持连接的消息对象。

 * <p>

 * 创建时间：2010-7-18 上午12:22:09

 * @author HouLei

 * @since 1.0

 */

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";

    }

}

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.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 = ;

        Client client = new Client(serverIp,port);

        client.start();

    }

    private String serverIp;

    private int port;

    private Socket socket;

    private boolean running=false;

    private long lastSendTime;

    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();

        new Thread(new ReceiveWatchDog()).start();

    }

    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 = ;

        long keepAliveDelay = ;

        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()>){

                        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();

                    }

                } catch (Exception e) {

                    e.printStackTrace();

                    Client.this.stop();

                } 

            }

        }

    }

}

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);

    }

    public static final class DefaultObjectAction implements ObjectAction{

        public Object doAction(Object rev) {

            System.out.println("处理并返回："+rev);

            return rev;

        }

    }

    public static void main(String[] args) {

        int port = ;

        Server server = new Server(port);

        server.start();

    }

    private int port;

    private volatile boolean running=false;

    private long receiveTimeDelay=;

    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,);

                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()>){

                            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);

                            if(out!=null){

                                ObjectOutputStream oos = new ObjectOutputStream(s.getOutputStream());

                                oos.writeObject(out);

                                oos.flush();

                            }

                        }else{

                            Thread.sleep();

                        }

                    } 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());

        }
    }
}