Tomcat 6支持的Comet

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今天在测试中无意中看到Tomcat 6的新特性Comet，使用Comet技术可以轻松实现一个Pushlet的功能，让我看了着实兴奋不已，而其官方网站还给出了一个Messenger的例子。

   
   
   
   

    
    
    
    

     
     
     
     

      
      
      
      public 
      
      
      
      class ChatServlet
     
     
     
     
    
    
    
    

     
     
     
     
    
      
      
      
      extends HttpServlet 
      
      
      
      implements CometProcessor 
      
      
      
      {
     
     
     
     
    
    
    
    

     
     
     
     

      
      
      
       
     
     
     
     
    
    
    
    

     
     
     
     
    
      
      
      
      protected ArrayList connections = 
     
     
     
     
    
    
    
    

     
     
     
     
        
      
      
      
      new ArrayList
      
      
      
      (
      
      
      
      );
     
     
     
     
    
    
    
    

     
     
     
     
    
      
      
      
      protected MessageSender messageSender = 
      
      
      
      null;
     
     
     
     
    
    
    
    
    
    
    
    
    

     
     
     
     
    
      
      
      
      public 
      
      
      
      void init
      
      
      
      (
      
      
      
      ) 
      
      
      
      throws ServletException 
      
      
      
      {
     
     
     
     
    
    
    
    

     
     
     
     

      
      
      
              messageSender = 
      
      
      
      new MessageSender
      
      
      
      (
      
      
      
      );
     
     
     
     
    
    
    
    

     
     
     
     
        
      
      
      
      Thread messageSenderThread = 
     
     
     
     
    
    
    
    

     
     
     
     
            
      
      
      
      new 
      
      
      
      Thread
      
      
      
      (messageSender, 
      
      
      
      "MessageSender[" + getServletContext
      
      
      
      (
      
      
      
      ).
      
      
      
      getContextPath
      
      
      
      (
      
      
      
      ) + 
      
      
      
      "]"
      
      
      
      );
     
     
     
     
    
    
    
    

     
     
     
     

      
      
      
              messageSenderThread.
      
      
      
      setDaemon
      
      
      
      (
      
      
      
      true
      
      
      
      );
     
     
     
     
    
    
    
    

     
     
     
     

      
      
      
              messageSenderThread.
      
      
      
      start
      
      
      
      (
      
      
      
      );
     
     
     
     
    
    
    
    

     
     
     
     
    
      
      
      
      }
     
     
     
     
    
    
    
    

     
     
     
     

      
      
      
       
     
     
     
     
    
    
    
    

     
     
     
     
    
      
      
      
      public 
      
      
      
      void destroy
      
      
      
      (
      
      
      
      ) 
      
      
      
      {
     
     
     
     
    
    
    
    

     
     
     
     

      
      
      
              connections.
      
      
      
      clear
      
      
      
      (
      
      
      
      );
     
     
     
     
    
    
    
    

     
     
     
     

      
      
      
              messageSender.
      
      
      
      stop
      
      
      
      (
      
      
      
      );
     
     
     
     
    
    
    
    

     
     
     
     

      
      
      
              messageSender = 
      
      
      
      null;
     
     
     
     
    
    
    
    

     
     
     
     
    
      
      
      
      }
     
     
     
     
    
    
    
    

     
     
     
     

      
      
      
       
     
     
     
     
    
    
    
    

     
     
     
     
    
      
      
      
      /**
     
     
     
     
    
    
    
    

     
     
     
     

      
      
      
           * Process the given Comet event.
     
     
     
     
    
    
    
    

     
     
     
     

      
      
      
           * 
     
     
     
     
    
    
    
    

     
     
     
     

      
      
      
           * @param event The Comet event that will be processed
     
     
     
     
    
    
    
    

     
     
     
     

      
      
      
           * @throws IOException
     
     
     
     
    
    
    
    

     
     
     
     

      
      
      
           * @throws ServletException
     
     
     
     
    
    
    
    

     
     
     
     

      
      
      
           */
     
     
     
     
    
    
    
    

     
     
     
     
    
      
      
      
      public 
      
      
      
      void event
      
      
      
      (CometEvent event
      
      
      
      )
     
     
     
     
    
    
    
    

     
     
     
     
        
      
      
      
      throws 
      
      
      
      IOException, ServletException 
      
      
      
      {
     
     
     
     
    
    
    
    

     
     
     
     

      
      
      
              HttpServletRequest request = event.
      
      
      
      getHttpServletRequest
      
      
      
      (
      
      
      
      );
     
     
     
     
    
    
    
    

     
     
     
     

      
      
      
              HttpServletResponse response = event.
      
      
      
      getHttpServletResponse
      
      
      
      (
      
      
      
      );
     
     
     
     
    
    
    
    

     
     
     
     
        
      
      
      
      if 
      
      
      
      (event.
      
      
      
      getEventType
      
      
      
      (
      
      
      
      ) == CometEvent.
      
      
      
      EventType.
      
      
      
      BEGIN
      
      
      
      ) 
      
      
      
      {
     
     
     
     
    
    
    
    

     
     
     
     

      
      
      
                  log
      
      
      
      (
      
      
      
      "Begin for session: " + request.
      
      
      
      getSession
      
      
      
      (
      
      
      
      true
      
      
      
      ).
      
      
      
      getId
      
      
      
      (
      
      
      
      )
      
      
      
      );
     
     
     
     
    
    
    
    

     
     
     
     
            
      
      
      
      PrintWriter writer = response.
      
      
      
      getWriter
      
      
      
      (
      
      
      
      );
     
     
     
     
    
    
    
    

     
     
     
     

      
      
      
                  writer.
      
      
      
      println
      
      
      
      (
      
      
      
      "\"-//w3c//dtd html 4.0 transitional//en\">"
      
      
      
      );
     
     
     
     
    
    
    
    

     
     
     
     

      
      
      
                  writer.
      
      
      
      println
      
      
      
      (
      
      
      
      "\"#FFFFFF\">"
      
      
      
      );
     
     
     
     
    
    
    
    

     
     
     
     

      
      
      
                  writer.
      
      
      
      flush
      
      
      
      (
      
      
      
      );
     
     
     
     
    
    
    
    

     
     
     
     
            
      
      
      
      synchronized
      
      
      
      (connections
      
      
      
      ) 
      
      
      
      {
     
     
     
     
    
    
    
    

     
     
     
     

      
      
      
                      connections.
      
      
      
      add
      
      
      
      (response
      
      
      
      );
     
     
     
     
    
    
    
    

     
     
     
     
            
      
      
      
      }
     
     
     
     
    
    
    
    

     
     
     
     
        
      
      
      
      } 
      
      
      
      else 
      
      
      
      if 
      
      
      
      (event.
      
      
      
      getEventType
      
      
      
      (
      
      
      
      ) == CometEvent.
      
      
      
      EventType.
      
      
      
      ERROR
      
      
      
      ) 
      
      
      
      {
     
     
     
     
    
    
    
    

     
     
     
     

      
      
      
                  log
      
      
      
      (
      
      
      
      "Error for session: " + request.
      
      
      
      getSession
      
      
      
      (
      
      
      
      true
      
      
      
      ).
      
      
      
      getId
      
      
      
      (
      
      
      
      )
      
      
      
      );
     
     
     
     
    
    
    
    

     
     
     
     
            
      
      
      
      synchronized
      
      
      
      (connections
      
      
      
      ) 
      
      
      
      {
     
     
     
     
    
    
    
    

     
     
     
     

      
      
      
                      connections.
      
      
      
      remove
      
      
      
      (response
      
      
      
      );
     
     
     
     
    
    
    
    

     
     
     
     
            
      
      
      
      }
     
     
     
     
    
    
    
    

     
     
     
     

      
      
      
                  event.
      
      
      
      close
      
      
      
      (
      
      
      
      );
     
     
     
     
    
    
    
    

     
     
     
     
        
      
      
      
      } 
      
      
      
      else 
      
      
      
      if 
      
      
      
      (event.
      
      
      
      getEventType
      
      
      
      (
      
      
      
      ) == CometEvent.
      
      
      
      EventType.
      
      
      
      END
      
      
      
      ) 
      
      
      
      {
     
     
     
     
    
    
    
    

     
     
     
     

      
      
      
                  log
      
      
      
      (
      
      
      
      "End for session: " + request.
      
      
      
      getSession
      
      
      
      (
      
      
      
      true
      
      
      
      ).
      
      
      
      getId
      
      
      
      (
      
      
      
      )
      
      
      
      );
     
     
     
     
    
    
    
    

     
     
     
     
            
      
      
      
      synchronized
      
      
      
      (connections
      
      
      
      ) 
      
      
      
      {
     
     
     
     
    
    
    
    

     
     
     
     

      
      
      
                      connections.
      
      
      
      remove
      
      
      
      (response
      
      
      
      );
     
     
     
     
    
    
    
    

     
     
     
     
            
      
      
      
      }
     
     
     
     
    
    
    
    

     
     
     
     
            
      
      
      
      PrintWriter writer = response.
      
      
      
      getWriter
      
      
      
      (
      
      
      
      );
     
     
     
     
    
    
    
    

     
     
     
     

      
      
      
                  writer.
      
      
      
      println
      
      
      
      (
      
      
      
      ""
      
      
      
      );
     
     
     
     
    
    
    
    

     
     
     
     

      
      
      
                  event.
      
      
      
      close
      
      
      
      (
      
      
      
      );
     
     
     
     
    
    
    
    

     
     
     
     
        
      
      
      
      } 
      
      
      
      else 
      
      
      
      if 
      
      
      
      (event.
      
      
      
      getEventType
      
      
      
      (
      
      
      
      ) == CometEvent.
      
      
      
      EventType.
      
      
      
      READ
      
      
      
      ) 
      
      
      
      {
     
     
     
     
    
    
    
    

     
     
     
     
            
      
      
      
      InputStream is = request.
      
      
      
      getInputStream
      
      
      
      (
      
      
      
      );
     
     
     
     
    
    
    
    

     
     
     
     
            
      
      
      
      byte
      
      
      
      [
      
      
      
      ] buf = 
      
      
      
      new 
      
      
      
      byte
      
      
      
      [
      
      
      
      512
      
      
      
      ];
     
     
     
     
    
    
    
    

     
     
     
     
            
      
      
      
      do 
      
      
      
      {
     
     
     
     
    
    
    
    

     
     
     
     
                
      
      
      
      int n = is.
      
      
      
      read
      
      
      
      (buf
      
      
      
      ); 
      
      
      
      //can throw an IOException
     
     
     
     
    
    
    
    

     
     
     
     
                
      
      
      
      if 
      
      
      
      (n > 
      
      
      
      0
      
      
      
      ) 
      
      
      
      {
     
     
     
     
    
    
    
    

     
     
     
     

      
      
      
                          log
      
      
      
      (
      
      
      
      "Read " + n + 
      
      
      
      " bytes: " + 
      
      
      
      new 
      
      
      
      String
      
      
      
      (buf, 
      
      
      
      0, n
      
      
      
      ) 
     
     
     
     
    
    
    
    

     
     
     
     

      
      
      
                                  + 
      
      
      
      " for session: " + request.
      
      
      
      getSession
      
      
      
      (
      
      
      
      true
      
      
      
      ).
      
      
      
      getId
      
      
      
      (
      
      
      
      )
      
      
      
      );
     
     
     
     
    
    
    
    

     
     
     
     
                
      
      
      
      } 
      
      
      
      else 
      
      
      
      if 
      
      
      
      (n < 
      
      
      
      0
      
      
      
      ) 
      
      
      
      {
     
     
     
     
    
    
    
    

     
     
     
     

      
      
      
                          error
      
      
      
      (event, request, response
      
      
      
      );
     
     
     
     
    
    
    
    

     
     
     
     
                    
      
      
      
      return;
     
     
     
     
    
    
    
    

     
     
     
     
                
      
      
      
      }
     
     
     
     
    
    
    
    

     
     
     
     
            
      
      
      
      } 
      
      
      
      while 
      
      
      
      (is.
      
      
      
      available
      
      
      
      (
      
      
      
      ) > 
      
      
      
      0
      
      
      
      );
     
     
     
     
    
    
    
    

     
     
     
     
        
      
      
      
      }
     
     
     
     
    
    
    
    

     
     
     
     
    
      
      
      
      }
     
     
     
     
    
    
    
    

     
     
     
     

      
      
      
       
     
     
     
     
    
    
    
    

     
     
     
     
    
      
      
      
      public 
      
      
      
      class MessageSender 
      
      
      
      implements 
      
      
      
      Runnable 
      
      
      
      {
     
     
     
     
    
    
    
    

     
     
     
     

      
      
      
       
     
     
     
     
    
    
    
    

     
     
     
     
        
      
      
      
      protected 
      
      
      
      boolean running = 
      
      
      
      true;
     
     
     
     
    
    
    
    

     
     
     
     
        
      
      
      
      protected ArrayList messages = 
      
      
      
      new ArrayList
      
      
      
      (
      
      
      
      );
     
     
     
     
    
    
    
    
        
    
    
    
    

     
     
     
     
        
      
      
      
      public MessageSender
      
      
      
      (
      
      
      
      ) 
      
      
      
      {
     
     
     
     
    
    
    
    

     
     
     
     
        
      
      
      
      }
     
     
     
     
    
    
    
    
        
    
    
    
    

     
     
     
     
        
      
      
      
      public 
      
      
      
      void stop
      
      
      
      (
      
      
      
      ) 
      
      
      
      {
     
     
     
     
    
    
    
    

     
     
     
     

      
      
      
                  running = 
      
      
      
      false;
     
     
     
     
    
    
    
    

     
     
     
     
        
      
      
      
      }
     
     
     
     
    
    
    
    

     
     
     
     

      
      
      
       
     
     
     
     
    
    
    
    

     
     
     
     
        
      
      
      
      /**
     
     
     
     
    
    
    
    

     
     
     
     

      
      
      
               * Add message for sending.
     
     
     
     
    
    
    
    

     
     
     
     

      
      
      
               */
     
     
     
     
    
    
    
    

     
     
     
     
        
      
      
      
      public 
      
      
      
      void send
      
      
      
      (
      
      
      
      String user, 
      
      
      
      String message
      
      
      
      ) 
      
      
      
      {
     
     
     
     
    
    
    
    

     
     
     
     
            
      
      
      
      synchronized 
      
      
      
      (messages
      
      
      
      ) 
      
      
      
      {
     
     
     
     
    
    
    
    

     
     
     
     

      
      
      
                      messages.
      
      
      
      add
      
      
      
      (
      
      
      
      "[" + user + 
      
      
      
      "]: " + message
      
      
      
      );
     
     
     
     
    
    
    
    

     
     
     
     

      
      
      
                      messages.
      
      
      
      notify
      
      
      
      (
      
      
      
      );
     
     
     
     
    
    
    
    

     
     
     
     
            
      
      
      
      }
     
     
     
     
    
    
    
    

     
     
     
     
        
      
      
      
      }
     
     
     
     
    
    
    
    

     
     
     
     

      
      
      
       
     
     
     
     
    
    
    
    

     
     
     
     
        
      
      
      
      public 
      
      
      
      void run
      
      
      
      (
      
      
      
      ) 
      
      
      
      {
     
     
     
     
    
    
    
    

     
     
     
     

      
      
      
       
     
     
     
     
    
    
    
    

     
     
     
     
            
      
      
      
      while 
      
      
      
      (running
      
      
      
      ) 
      
      
      
      {
     
     
     
     
    
    
    
    

     
     
     
     

      
      
      
       
     
     
     
     
    
    
    
    

     
     
     
     
                
      
      
      
      if 
      
      
      
      (messages.
      
      
      
      size
      
      
      
      (
      
      
      
      ) == 
      
      
      
      0
      
      
      
      ) 
      
      
      
      {
     
     
     
     
    
    
    
    

     
     
     
     
                    
      
      
      
      try 
      
      
      
      {
     
     
     
     
    
    
    
    

     
     
     
     
                        
      
      
      
      synchronized 
      
      
      
      (messages
      
      
      
      ) 
      
      
      
      {
     
     
     
     
    
    
    
    

     
     
     
     

      
      
      
                                  messages.
      
      
      
      wait
      
      
      
      (
      
      
      
      );
     
     
     
     
    
    
    
    

     
     
     
     
                        
      
      
      
      }
     
     
     
     
    
    
    
    

     
     
     
     
                    
      
      
      
      } 
      
      
      
      catch 
      
      
      
      (
      
      
      
      InterruptedException e
      
      
      
      ) 
      
      
      
      {
     
     
     
     
    
    
    
    

     
     
     
     
                        
      
      
      
      // Ignore
     
     
     
     
    
    
    
    

     
     
     
     
                    
      
      
      
      }
     
     
     
     
    
    
    
    

     
     
     
     
                
      
      
      
      }
     
     
     
     
    
    
    
    

     
     
     
     

      
      
      
       
     
     
     
     
    
    
    
    

     
     
     
     
                
      
      
      
      synchronized 
      
      
      
      (connections
      
      
      
      ) 
      
      
      
      {
     
     
     
     
    
    
    
    

     
     
     
     
                    
      
      
      
      String
      
      
      
      [
      
      
      
      ] pendingMessages = 
      
      
      
      null;
     
     
     
     
    
    
    
    

     
     
     
     
                    
      
      
      
      synchronized 
      
      
      
      (messages
      
      
      
      ) 
      
      
      
      {
     
     
     
     
    
    
    
    

     
     
     
     

      
      
      
                              pendingMessages = messages.
      
      
      
      toArray
      
      
      
      (
      
      
      
      new 
      
      
      
      String
      
      
      
      [
      
      
      
      0
      
      
      
      ]
      
      
      
      );
     
     
     
     
    
    
    
    

     
     
     
     

      
      
      
                              messages.
      
      
      
      clear
      
      
      
      (
      
      
      
      );
     
     
     
     
    
    
    
    

     
     
     
     
                    
      
      
      
      }
     
     
     
     
    
    
    
    

     
     
     
     
                    
      
      
      
      // Send any pending message on all the open connections
     
     
     
     
    
    
    
    

     
     
     
     
                    
      
      
      
      for 
      
      
      
      (
      
      
      
      int i = 
      
      
      
      0; i < connections.
      
      
      
      size
      
      
      
      (
      
      
      
      ); i++
      
      
      
      ) 
      
      
      
      {
     
     
     
     
    
    
    
    

     
     
     
     
                        
      
      
      
      try 
      
      
      
      {
     
     
     
     
    
    
    
    

     
     
     
     
                            
      
      
      
      PrintWriter writer = connections.
      
      
      
      get
      
      
      
      (i
      
      
      
      ).
      
      
      
      getWriter
      
      
      
      (
      
      
      
      );
     
     
     
     
    
    
    
    

     
     
     
     
                            
      
      
      
      for 
      
      
      
      (
      
      
      
      int j = 
      
      
      
      0; j < pendingMessages.
      
      
      
      length; j++
      
      
      
      ) 
      
      
      
      {
     
     
     
     
    
    
    
    

     
     
     
     

      
      
      
                                      writer.
      
      
      
      println
      
      
      
      (pendingMessages
      
      
      
      [j
      
      
      
      ] + 
      
      
      
      "
"
      
      
      
      );
     
     
     
     
    
    
    
    

     
     
     
     
                            
      
      
      
      }
     
     
     
     
    
    
    
    

     
     
     
     

      
      
      
                                  writer.
      
      
      
      flush
      
      
      
      (
      
      
      
      );
     
     
     
     
    
    
    
    

     
     
     
     
                        
      
      
      
      } 
      
      
      
      catch 
      
      
      
      (
      
      
      
      IOException e
      
      
      
      ) 
      
      
      
      {
     
     
     
     
    
    
    
    

     
     
     
     

      
      
      
                                  log
      
      
      
      (
      
      
      
      "IOExeption sending message", e
      
      
      
      );
     
     
     
     
    
    
    
    

     
     
     
     
                        
      
      
      
      }
     
     
     
     
    
    
    
    

     
     
     
     
                    
      
      
      
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