tomcat+comet实现终端与服务端同步的小例子

1、 工程说明
    java project——CometSocket包含一个类：
          Calculate.java：作为客户端，往服务器发送数据 

    web project——CometServer包含：
         ReceiverServlet.java：接收客户端数据，并模拟入库（以存入文件的形式）
         TestServlet.java：模拟从库中取数据（从文件中取值）并推送给浏览器展示
         index.jsp：接收从服务端推送出来的数据并展示

2、部分代码说明
     Calculate.java
    

 public void sendData(ActionEvent e)
    {
        
      try
    {
            //发送数据
            txtResult.setText(e.getActionCommand());
            URL url = new URL("http://localhost:8080/CometServer/rs?num="+txtResult.getText());
            HttpURLConnection httpURLConnection = (HttpURLConnection)url.openConnection();
            httpURLConnection.setRequestProperty("Content-Type", "text/html"); //application/xml
            httpURLConnection.setRequestMethod("GET");
            httpURLConnection.setReadTimeout(2*1000);
            int code = httpURLConnection.getResponseCode();
            System.out.println("code_______________"+code);
    }

     通过http get请求方式将数据发送给客户端

    ReceiverServlet.java   

public void service(HttpServletRequest request ,HttpServletResponse response){
        FileOutputStream fos = null;
        try
        {
            String str = request.getParameter("num");
            System.out.println("get________________________________"+str);
            File file = new File("D:/1.txt");
            fos = new FileOutputStream(file);
            if(str != null){
                fos.write(str.getBytes());
            }
            
        }
        catch (FileNotFoundException e)
        {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        catch (IOException e)
        {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }finally{
            if(fos != null){
                try
                {
                    fos.close();
                }
                catch (IOException e)
                {
                    // TODO Auto-generated catch block
                    e.printStackTrace();
                }
            }
            
        }
    }

    接收数据并模拟入库

    TestServlet.java
   

public void event(CometEvent event) throws IOException, ServletException
    {
        // 开始
        if(event.getEventType() == EventType.BEGIN){
            try
            {
                Thread.sleep(100);    
                File file = new File ("D:/1.txt");
                BufferedReader br = new BufferedReader(new InputStreamReader(new FileInputStream(file)));
                String str = br.readLine();

                System.out.println("ddd1_________"+str);  
                if( str != null){
                    HttpServletResponse response = event.getHttpServletResponse();
                    PrintWriter out = response.getWriter();
                    out.write(str);
                    out.flush();  
                    out.close();
                }
            }
            catch (Exception e)
            {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
            
          }
        if(event.getEventType() == EventType.END){
            System.out.println("ddd2");
            event.close();
        }
        
        
    }

     定时向服务器推送数据
   
3、运行   
   tomcat配置： 要使用 Comet，需要对 Tomcat 的配置文件 server.xml 稍作修改。默认情况下启用的是更典型的同步 IO 连接器。现在只需将它切换成异步版本.
  <!-- Connector URIEncoding="utf-8" connectionTimeout="20000" port="8080" protocol="HTTP/1.1" redirectPort="8443"/ -->
<Connector connectionTimeout="20000" port="8080" protocol="org.apache.
coyote.http11.Http11NioProtocol" redirectPort="8443"/>

源码和效果图，如附件：

   启动web工程，点击“start”
   运行Calculate.java