Tomcat example source code file (ChatServlet.java)

This example Tomcat source code file (ChatServlet.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" ^TM.

Java - Tomcat tags/keywords

arraylist, chat, http, httpservletrequest, httpservletresponse, httpservletresponse, io, ioexception, ioexception, messagesender, messagesender, printwriter, request, response, servlet, servletexception, servletexception, string, thread, util

The Tomcat ChatServlet.java source code

/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 * 
 *      http://www.apache.org/licenses/LICENSE-2.0
 * 
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */


package chat;


import java.io.IOException;
import java.io.InputStream;
import java.io.PrintWriter;
import java.util.ArrayList;

import org.apache.catalina.CometEvent;
import org.apache.catalina.CometProcessor;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;


/**
 * Helper class to implement Comet functionality.
 */
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 {

        // Note: There should really be two servlets in this example, to avoid
        // mixing Comet stuff with regular connection processing
        HttpServletRequest request = event.getHttpServletRequest();
        HttpServletResponse response = event.getHttpServletResponse();
        
        if (event.getEventType() == CometEvent.EventType.BEGIN) {
            begin(event, request, response);
        } else if (event.getEventType() == CometEvent.EventType.ERROR) {
            error(event, request, response);
        } else if (event.getEventType() == CometEvent.EventType.END) {
            end(event, request, response);
        } else if (event.getEventType() == CometEvent.EventType.READ) {
            read(event, request, response);
        }
    }

    protected void begin(CometEvent event, HttpServletRequest request, HttpServletResponse response)
        throws IOException, ServletException {
        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("<html>JSP Chat");
        writer.flush();

        System.out.println("Action param: " + request.getParameter("action"));
        synchronized(connections) {
            connections.add(response);
        }
    }
    
    protected void end(CometEvent event, HttpServletRequest request, HttpServletResponse response)
        throws IOException, ServletException {
        log("End for session: " + request.getSession(true).getId());
        synchronized(connections) {
            connections.remove(response);
        }
        
        PrintWriter writer = response.getWriter();
        writer.println("</body>");
        
        event.close();
        
    }
    
    protected void error(CometEvent event, HttpServletRequest request, HttpServletResponse response)
        throws IOException, ServletException {
        log("Error for session: " + request.getSession(true).getId());
        synchronized(connections) {
            connections.remove(response);
        }
        event.close();
    }
    
    protected void read(CometEvent event, HttpServletRequest request, HttpServletResponse response)
        throws IOException, ServletException {
        log("Read for session: " + request.getSession(true).getId());
        /*
        InputStream is = request.getInputStream();
        byte[] buf = new byte[512];
        while (is.available() > 0) {
            log("Available: " + is.available());
            int n = is.read(buf);
            if (n > 0) {
                log("Read " + n + " bytes: " + new String(buf, 0, n) 
                        + " for session: " + request.getSession(true).getId());
            } else if (n < 0) {
                log("End of file: " + n);
                end(event, request, response);
                return;
            }
        }*/
    }

    protected void service(HttpServletRequest request, HttpServletResponse response)
        throws IOException, ServletException {
        // Compatibility method: equivalent method using the regular connection model
        PrintWriter writer = response.getWriter();
        writer.println("<!doctype html public \"-//w3c//dtd html 4.0 transitional//en\">");
        writer.println("<html>JSP Chat");
        writer.println("Chat example only supports Comet processing");
        writer.println("</body>");
    }
    

    /**
     * Poller class.
     */
    public class MessageSender implements Runnable {

        protected boolean running = true;
        protected ArrayList<String> messages = new ArrayList();
        
        public MessageSender() {
        }
        
        public void stop() {
            running = false;
        }

        /**
         * Add specified socket and associated pool to the poller. The socket will
         * be added to a temporary array, and polled first after a maximum amount
         * of time equal to pollTime (in most cases, latency will be much lower,
         * however).
         *
         * @param socket to add to the poller
         */
        public void send(String user, String message) {
            synchronized (messages) {
                messages.add("[" + user + "]: " + message);
                messages.notify();
            }
        }

        /**
         * The background thread that listens for incoming TCP/IP connections and
         * hands them off to an appropriate processor.
         */
        public void run() {

            // Loop until we receive a shutdown command
            while (running) {
                // Loop if endpoint is paused

                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();
                    }
                    for (int i = 0; i < connections.size(); i++) {
                        try {
                            PrintWriter writer = connections.get(i).getWriter();
                            for (int j = 0; j < pendingMessages.length; j++) {
                                // FIXME: Add HTML filtering
                                writer.println(pendingMessages[j] + "<br/>");
                            }
                            writer.flush();
                        } catch (IOException e) {
                            log("IOExeption sending message", e);
                        }
                    }
                }

            }

        }

    }




}

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Tomcat example source code file (ChatServlet.java)

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The Tomcat ChatServlet.java source code

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