content: //========================================================================
  //Copyright 2006 Mort Bay Consulting Pty. Ltd.
  //------------------------------------------------------------------------
  //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.apache.activemq.web;
  
  import java.io.ByteArrayOutputStream;
  import java.io.IOException;
  import java.io.InputStream;
  import java.net.URL;
  import java.util.HashMap;
  import java.util.Map;
  
  import jakarta.servlet.ServletException;
  import jakarta.servlet.http.HttpServletRequest;
  import jakarta.servlet.http.HttpServletResponse;
  
  /* ------------------------------------------------------------ */
  /**
   * AjaxServlet. The AjaxServlet extends the {@link MessageListenerServlet} with
   * the capability to server the <code>amq.js</code> script and associated
   * scripts from resources within the activemq-web jar. The amq.js script is the
   * client side companion to the MessageListenerServlet and supports sending
   * messages and long polling for receiving messages (Also called Comet style
   * Ajax).
   */
  public class AjaxServlet extends MessageListenerServlet {
  
      private static final long serialVersionUID = -3875280764356406114L;
      private Map<String, byte[]> jsCache = new HashMap<String, byte[]>();
      private long jsLastModified = 1000 * (System.currentTimeMillis() / 1000);
  
      protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
          if (request.getPathInfo() != null && request.getPathInfo().endsWith(".js")) {
              doJavaScript(request, response);
          } else {
              super.doGet(request, response);
          }
      }
  
      protected void doJavaScript(HttpServletRequest request, HttpServletResponse response) throws IOException, ServletException {
  
          // Look for a local resource first.
          String js = request.getServletPath() + request.getPathInfo();
          URL url = getServletContext().getResource(js);
          if (url != null) {
              getServletContext().getNamedDispatcher("default").forward(request, response);
              return;
          }
  
          // Serve from the classpath resources
          String resource = "org/apache/activemq/web" + request.getPathInfo();
          synchronized (jsCache) {
  
              byte[] data = jsCache.get(resource);
              if (data == null) {
                  try(InputStream in = Thread.currentThread().getContextClassLoader().getResourceAsStream(resource)) {
                      if (in != null) {
                          try(ByteArrayOutputStream out = new ByteArrayOutputStream()) {
                              byte[] buf = new byte[4096];
                              int len = in.read(buf);
                              while (len >= 0) {
                                  out.write(buf, 0, len);
                                  len = in.read(buf);
                              }
                              data = out.toByteArray();
                              jsCache.put(resource, data);
                          }
                      }
                  }
              }
  
              if (data != null) {
  
                  long ifModified = request.getDateHeader("If-Modified-Since");
  
                  if (ifModified == jsLastModified) {
                      response.sendError(HttpServletResponse.SC_NOT_MODIFIED);
                  } else {
                      response.setContentType("application/x-javascript");
                      response.setContentLength(data.length);
                      response.setDateHeader("Last-Modified", jsLastModified);
                      response.getOutputStream().write(data);
                  }
              } else {
                  response.sendError(HttpServletResponse.SC_NOT_FOUND);
              }
          }
      }
  }
  