应用comet时,怎么可以从服务器推复杂的内容到浏览器？

liguicheng2006 2009-09-17 04:12:35

请问，在comet时，一般是服务器servlet用一个PrintWriter将要发送的数据传出去，浏览器在javascript脚本里用XMLHttpRequest得到responseText，这个responseText就是服务器发过来的新数据。
而PrintWriter.write()方法的参数类型是char,int,String，想问一下，应该如何将复杂的数据传出去？请大家说一下有什么方法
当然，我也知道可以在服务器端传出数据前将数据组成一串字符，但后面还要在javascript中解析这串字符，因为对javascript不是太熟悉，所以觉得麻烦。
不知道有没有办法在javascript里的responseText传给当前jsp页面里的java代码呢？这就可以在服务器端将数据打包成字节流,再在页面解开（简单查了一下，说javascript是浏览器解析，jsp是服务器编译解析，所以不行，不过未认真想过）
共享网上抄来的代码，本人实验过，是可行的（tomcat 6,firefox打开）。



/**

 * Servlet implementation class CometServlet

 */

public class CometServlet extends HttpServlet implements CometProcessor{

	private static final long serialVersionUID = 1L;

//	private HttpServletRequest request;

	private String word = "Hello World" ;

	

       

    /**

     * @see HttpServlet#HttpServlet()

     */

    public CometServlet() {

        super();

        // TODO Auto-generated constructor stub

    }



	@Override

	public void event(CometEvent e) throws IOException, ServletException {

		// TODO Auto-p method stub

		if(e.getEventType() == EventType.BEGIN){

			HttpServletResponse response = e.getHttpServletResponse();

			RadomNumber ran = new RadomNumber(response);

			new Thread(ran).start();

		} else if(e.getEventType() == EventType.READ){

			

		}

	}

	

	

	private class RadomNumber implements Runnable{

		

		private ServletResponse connection;

		

		RadomNumber(ServletResponse response){

			this.connection = response;

		}



		@Override

		public void run() {

			// TODO Auto-generated method stub



			String ran = null;

			while (word != null) {

				PrintWriter out = null;

				ran = String.valueOf(Math.random());

				if (!ran.equals(word)) {

					try {

						out = connection.getWriter();

					} catch (IOException e) {

						// TODO Auto-generated catch block

						e.printStackTrace();

					}

					out.write(word);

					out.println();

					out.flush();

					try {

						Thread.sleep(5000L);

					} catch (InterruptedException e) {

						// TODO Auto-generated catch block

						e.printStackTrace();

					}

					word = ran;

				}

			}

		}

		

	}



<html>

<head>

<meta http-equiv="Content-Type" content="text/html; charset=GB18030">

<title>Insert title here</title>

 <script>

 function   storeCaret   (textEl)   {  

	  if   (textEl.createTextRange)    

	  textEl.caretPos   =   document.selection.createRange().duplicate();    

	  }

 

 var http_request = false;

 

 function CometEx(text) {

	 if(window.XMLHttpRequest){//Mozilla browser

		 http_request = new XMLHttpRequest();

	 	 if(http_request.overrideMineType){//set MiME type

		 	 http_request.overrideMineType('test/xml');

	 	 }

	 }else if(window.ActiveXObject){//IE browser 不过好像没用,不能在IE上显示.

		 try{

			 http_request = new ActiveXObject("Msxml2.XMLHTTP");

		 }catch(e){

			 try{

				 http_request = new ActiveXObject(Microsoft.XMLHTTP);

				 }catch(e){}

			 }

	 }

	 if(!http_request){//can not creat HttpRequest

		 window.alert("can not creat HttpRequest");

	 	 return false;

		 }

   //var request =  new XMLHttpRequest();

   //request.open("GET", 'http://localhost:8080/MyComet/CometServlet', true);

   http_request.open("GET", 'http://localhost:8080/MyComet/CometServlet', true);

   http_request.onreadystatechange = function() {

     if (http_request.readyState == 3 && http_request.status == 200) {

          //alert(request.responseText);     

          text.value = http_request.responseText;

          

     }

   };

   http_request.send(null);

 }

 </script>

</head>

<body>

<FORM   NAME="aForm">  

  <TEXTAREA   NAME="aTextArea"   ROWS="5"   COLS="80"   WRAP="soft"   ONSELECT="storeCaret(this);"   ONCLICK="storeCaret(this);"   ONKEYUP="storeCaret(this);">   value:   </TEXTAREA>    

  <BR>     

  <INPUT   TYPE="button"   VALUE="Go!"   ONCLICK="CometEx(this.form.aTextArea);">  

</FORM> 



</body>

</html>