Tomcat 6で実現！Ajaxを超える通信技術Comet：Tomcatはどこまで“安全”にできるのか？（3）（3/3 ページ）

» 2007年12月12日 00時00分公開

[x-labチーム，株式会社アメニクス]

サーブレットにCometを実装する

　移動したら、サーブレットの作成に移ります。Cometはイベント受信後、エディタでCometServlet.javaを作成します。サーブレットには、以下の内容を記述していきます。

CometServlet.java（※Tomcatのリファレンスページにある内容を基に作成）

import java.util.*;

                      

                      import javax.servlet.ServletException;

                      import javax.servlet.http.HttpServlet;

                      import javax.servlet.http.HttpServletRequest;

                      import javax.servlet.http.HttpServletResponse;

                      

                      import org.apache.catalina.CometEvent;

                      import org.apache.catalina.CometProcessor;

                      

                      public class CometServlet

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 ("POST".equals(request.getMethod())) {

            final String user = request.getParameter("user");

            final String message = request.getParameter("message");

            messageSender.send(user,message);



            event.close();

            return;

        }



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

            event.setTimeout(60 * 1000 * 30);

            log("Begin for session: " 

                + request.getSession(true).getId());



            response.setContentType("text/html;charset=UTF-8");

            PrintWriter writer = response.getWriter();

            writer.println("<!doctype html public \"-//w3c//dtd html"

                +" 4.0 transitional//en\">");

            writer.println("<head><title>チャットメッセージ</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){

        }

        }

    

    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[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] 

                                    + "<br>");

                            }

                            writer.flush();

                        } catch (IOException e) {

                            log("IOExeption sending message", e);

                        }

                    }

                }

            }

        }

    }

}