JAVA长连接demo

package houlei.csdn.keepalive;

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())+"	维持连接包";
    }

}

package houlei.csdn.keepalive;

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：	"+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;
    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：	"+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：	"+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 houlei.csdn.keepalive;


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 = 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：	"+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(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());
        }

    }

}

大致解释一下什么意思：

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。