Java tutorial
/** * $RCSfile$ * $Revision: $ * $Date: $ * * Copyright (C) 2005-2008 B5Chat Community. All rights reserved. * * Licensed 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 org.b5chat.crossfire.web; import org.apache.commons.httpclient.HttpClient; import org.apache.commons.httpclient.MultiThreadedHttpConnectionManager; import org.apache.commons.httpclient.methods.GetMethod; import org.apache.commons.httpclient.params.HttpConnectionManagerParams; import org.b5chat.crossfire.core.util.cache.Cache; import org.b5chat.crossfire.core.util.cache.CacheFactory; import javax.servlet.ServletConfig; import javax.servlet.ServletException; import javax.servlet.ServletOutputStream; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; import java.io.*; import java.net.MalformedURLException; import java.net.URL; import java.net.URLConnection; /** * Servlet that gets favicons of webservers and includes them in HTTP responses. This * servlet can be used when getting a favicon can take some time so pages can use this * servlet as the image source to let the page load quickly and get the favicon images * as they are available.<p> * * This servlet expects the web application to have the <tt>images/server_16x16.gif</tt> * file that is used when no favicon is found. * * @author Gaston Dombiak */ public class FaviconServlet extends HttpServlet { /** * The content-type of the images to return. */ private static final String CONTENT_TYPE = "image/x-icon"; /** * Bytes of the default favicon to return when one was not found on a host. */ private byte[] defaultBytes; /** * Pool of HTTP connections to use to get the favicons */ private HttpClient client; /** * Cache the domains that a favicon was not found. */ private Cache<String, Integer> missesCache; /** * Cache the favicons that we've found. */ private Cache<String, byte[]> hitsCache; @Override public void init(ServletConfig config) throws ServletException { super.init(config); // Create a pool of HTTP connections to use to get the favicons client = new HttpClient(new MultiThreadedHttpConnectionManager()); HttpConnectionManagerParams params = client.getHttpConnectionManager().getParams(); params.setConnectionTimeout(2000); params.setSoTimeout(2000); // Load the default favicon to use when no favicon was found of a remote host try { URL resource = config.getServletContext().getResource("/images/server_16x16.gif"); defaultBytes = getImage(resource.toString()); } catch (MalformedURLException e) { e.printStackTrace(); } // Initialize caches. missesCache = CacheFactory.createCache("Favicon Misses"); hitsCache = CacheFactory.createCache("Favicon Hits"); } /** * Retrieve the image based on it's name. * * @param request the httpservletrequest. * @param response the httpservletresponse. * @throws javax.servlet.ServletException * @throws java.io.IOException */ @Override public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { String host = request.getParameter("host"); // Check special cases where we need to change host to get a favicon host = "gmail.com".equals(host) ? "google.com" : host; byte[] bytes = getImage(host, defaultBytes); if (bytes != null) { writeBytesToStream(bytes, response); } } /** * Writes out a <code>byte</code> to the ServletOuputStream. * * @param bytes the bytes to write to the <code>ServletOutputStream</code>. */ private void writeBytesToStream(byte[] bytes, HttpServletResponse response) { response.setContentType(CONTENT_TYPE); // Send image try { ServletOutputStream sos = response.getOutputStream(); sos.write(bytes); sos.flush(); sos.close(); } catch (IOException e) { // Do nothing } } /** * Returns the favicon image bytes of the specified host. * * @param host the name of the host to get its favicon. * @return the image bytes found, otherwise null. */ private byte[] getImage(String host, byte[] defaultImage) { // If we've already attempted to get the favicon twice and failed, // return the default image. if (missesCache.get(host) != null && missesCache.get(host) > 1) { // Domain does not have a favicon so return default icon return defaultImage; } // See if we've cached the favicon. if (hitsCache.containsKey(host)) { return hitsCache.get(host); } byte[] bytes = getImage("http://" + host + "/favicon.ico"); if (bytes == null) { // Cache that the requested domain does not have a favicon. Check if this // is the first cache miss or the second. if (missesCache.get(host) != null) { missesCache.put(host, 2); } else { missesCache.put(host, 1); } // Return byte of default icon bytes = defaultImage; } // Cache the favicon. else { hitsCache.put(host, bytes); } return bytes; } private byte[] getImage(String url) { try { // Try to get the fiveicon from the url using an HTTP connection from the pool // that also allows to configure timeout values (e.g. connect and get data) GetMethod get = new GetMethod(url); get.setFollowRedirects(true); int response = client.executeMethod(get); if (response < 400) { // Check that the response was successful. Should we also filter 30* code? return get.getResponseBody(); } else { // Remote server returned an error so return null return null; } } catch (IllegalStateException e) { // Something failed (probably a method not supported) so try the old stye now try { URLConnection urlConnection = new URL(url).openConnection(); urlConnection.setReadTimeout(1000); urlConnection.connect(); DataInputStream di = new DataInputStream(urlConnection.getInputStream()); ByteArrayOutputStream byteStream = new ByteArrayOutputStream(); DataOutputStream out = new DataOutputStream(byteStream); int len; byte[] b = new byte[1024]; while ((len = di.read(b)) != -1) { out.write(b, 0, len); } di.close(); out.flush(); return byteStream.toByteArray(); } catch (IOException ioe) { // We failed again so return null return null; } } catch (IOException ioe) { // We failed so return null return null; } } }