我目前正在编写一个 Comet 应用程序,它要求我在持久连接上一次发送大量数据。但是,在关闭连接之前,我无法将消息刷新到客户端。是否有任何原因 PrintWriter.flush() 方法的行为不像我认为的那样?
这是我的 Tomcat Comet 实现:
public void event(CometEvent event) throws IOException, ServletException {
HttpServletRequest request = event.getHttpServletRequest();
HttpServletResponse response = event.getHttpServletResponse();
if (event.getEventType() == EventType.BEGIN) {
request.setAttribute("org.apache.tomcat.comet.timeout", 300 * 1000);
PrintWriter out = response.getWriter();
out.println("BEGIN!");
out.flush();
System.out.println("EventType.BEGIN");
} else if (event.getEventType() == EventType.READ) {
InputStream is = request.getInputStream();
byte[] buf = new byte[512];
do {
int n = is.read(buf); //can throw an IOException
if (n > 0) {
System.out.println("Read " + n + " bytes: " + new String(buf, 0, n)
+ " for session: " + request.getSession(true).getId());
} else if (n < 0) {
return;
}
} while (is.available() > 0);
System.out.println("subtype: "+event.getEventSubType());
System.out.println("EventType.READ");
} else if (event.getEventType() == EventType.END) {
PrintWriter out = response.getWriter();
out.println("END!");
out.close();
System.out.println("checkError: "+out.checkError());
System.out.println(event.getEventSubType());
System.out.println("EventType.END");
//eventWorker.enqueue(new EndEvent(request, response));
} else if (event.getEventType() == EventType.ERROR) {
PrintWriter out = response.getWriter();
out.println("ERROR!");
out.flush();
System.out.println("checkError: "+out.checkError());
System.out.println("subtype: "+event.getEventSubType());
//response.getWriter().close();
System.out.println("EventType.ERROR");
} else {
(new ServletException("EXCEPTION")).printStackTrace();
}
}
所以在这里我试图发送消息“BEGIN!” 并在之后保持连接打开,以便我可以发送更多数据。但是,似乎在连接关闭之前消息不会通过。
这是我的 ajax 代码: $.post('comet', function(data) { alert(data); });
运行此代码后,Firebug 告诉我这是响应标头: Server: Apache-Coyote/1.1 Transfer-Encoding: chunked Date: Mon, 13 Jul 2009 21:16:29 GMT
这让我认为我的浏览器收到了一些数据,但是如何在连接关闭之前更新页面上的内容?