content: /**
   * 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 org.apache.activemq.web;
  
  import java.util.LinkedList;
  
  import jakarta.jms.Message;
  import jakarta.jms.MessageConsumer;
  
  import org.apache.activemq.MessageAvailableListener;
  import org.apache.activemq.web.async.AsyncServletRequest;
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  
  /*
   * Listen for available messages and wakeup any asyncRequests.
   */
  public class AjaxListener implements MessageAvailableListener {
      private static final Logger LOG = LoggerFactory.getLogger(AjaxListener.class);
  
      private final long maximumReadTimeout;
      private final AjaxWebClient client;
      private long lastAccess;
      private AsyncServletRequest asyncRequest;
      private final LinkedList<UndeliveredAjaxMessage> undeliveredMessages = new LinkedList<UndeliveredAjaxMessage>();
  
      AjaxListener(AjaxWebClient client, long maximumReadTimeout) {
          this.client = client;
          this.maximumReadTimeout = maximumReadTimeout;
          access();
      }
  
      public void access() {
          lastAccess = System.currentTimeMillis();
      }
  
      public synchronized void setAsyncRequest(AsyncServletRequest asyncRequest) {
          this.asyncRequest = asyncRequest;
      }
  
      public LinkedList<UndeliveredAjaxMessage> getUndeliveredMessages() {
          return undeliveredMessages;
      }
  
      @Override
      public synchronized void onMessageAvailable(MessageConsumer consumer) {
          LOG.debug("Message for consumer: {} asyncRequest: {}", consumer, asyncRequest);
  
          if (asyncRequest != null) {
              try {
                  Message message = consumer.receive(10);
                  LOG.debug("message is " + message);
                  if (message != null) {
                      if (!asyncRequest.isDispatched()) {
                          LOG.debug("Resuming suspended asyncRequest {}", asyncRequest);
                          asyncRequest.setAttribute("undelivered_message", new UndeliveredAjaxMessage(message, consumer));
                          asyncRequest.dispatch();
                      } else {
                          LOG.debug("Message available, but asyncRequest is already resumed. Buffer for next time.");
                          bufferMessageForDelivery(message, consumer);
                      }
                  }
              } catch (Exception e) {
                  LOG.warn("Error receiving message " + e.getMessage() + ". This exception is ignored.", e);
              }
  
          } else if (System.currentTimeMillis() - lastAccess > 2 * this.maximumReadTimeout) {
              new Thread() {
                  @Override
                  public void run() {
                      LOG.debug("Closing consumers on client: {}", client);
                      client.closeConsumers();
                  }
              }.start();
          } else {
              try {
                  Message message = consumer.receive(10);
                  bufferMessageForDelivery(message, consumer);
              } catch (Exception e) {
                  LOG.warn("Error receiving message " + e.getMessage() + ". This exception is ignored.", e);
              }
          }
      }
  
      public void bufferMessageForDelivery(Message message, MessageConsumer consumer) {
          if (message != null) {
              synchronized (undeliveredMessages) {
                  undeliveredMessages.addLast(new UndeliveredAjaxMessage(message, consumer));
              }
          }
      }
  }
  