Tomcat 6支持的Comet
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<HttpServletResponse> connections =
[*] new ArrayList<HttpServletResponse>();
[*] 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("<!doctype html public \"-//w3c//dtd html 4.0 transitional//en\">");
[*] writer.println("<head><title>JSP Chat</title></head><body bgcolor=\"#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("</body></html>");
[*] event.close();
[*] } else if (event.getEventType() == CometEvent.EventType.READ) {
[*] InputStream is = request.getInputStream();
[*] byte[] buf = new byte;
[*] 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<String> messages = new ArrayList<String>();
[*]
[*] 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);
[*] 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 + "<br>");
[*] }
[*] writer.flush();
[*] } catch (IOException e) {
[*] log("IOExeption sending message", e);
[*] }
[*] }
[*] }
[*]
[*] }
[*]
[*] }
[*]
[*] }
[*]
[*]}
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