001/** 002 * Licensed to the Apache Software Foundation (ASF) under one or more 003 * contributor license agreements. See the NOTICE file distributed with 004 * this work for additional information regarding copyright ownership. 005 * The ASF licenses this file to You under the Apache License, Version 2.0 006 * (the "License"); you may not use this file except in compliance with 007 * the License. You may obtain a copy of the License at 008 * 009 * http://www.apache.org/licenses/LICENSE-2.0 010 * 011 * Unless required by applicable law or agreed to in writing, software 012 * distributed under the License is distributed on an "AS IS" BASIS, 013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 014 * See the License for the specific language governing permissions and 015 * limitations under the License. 016 */ 017package org.apache.activemq.web; 018 019import java.util.LinkedList; 020 021import javax.jms.Message; 022import javax.jms.MessageConsumer; 023 024import org.apache.activemq.MessageAvailableListener; 025import org.eclipse.jetty.continuation.Continuation; 026import org.slf4j.Logger; 027import org.slf4j.LoggerFactory; 028 029/* 030 * Listen for available messages and wakeup any continuations. 031 */ 032public class AjaxListener implements MessageAvailableListener { 033 private static final Logger LOG = LoggerFactory.getLogger(AjaxListener.class); 034 035 private final long maximumReadTimeout; 036 private final AjaxWebClient client; 037 private long lastAccess; 038 private Continuation continuation; 039 private final LinkedList<UndeliveredAjaxMessage> undeliveredMessages = new LinkedList<UndeliveredAjaxMessage>(); 040 041 AjaxListener(AjaxWebClient client, long maximumReadTimeout) { 042 this.client = client; 043 this.maximumReadTimeout = maximumReadTimeout; 044 access(); 045 } 046 047 public void access() { 048 lastAccess = System.currentTimeMillis(); 049 } 050 051 public synchronized void setContinuation(Continuation continuation) { 052 this.continuation = continuation; 053 } 054 055 public LinkedList<UndeliveredAjaxMessage> getUndeliveredMessages() { 056 return undeliveredMessages; 057 } 058 059 @Override 060 public synchronized void onMessageAvailable(MessageConsumer consumer) { 061 LOG.debug("Message for consumer: {} continuation: {}", consumer, continuation); 062 063 if (continuation != null) { 064 try { 065 Message message = consumer.receive(10); 066 LOG.debug("message is " + message); 067 if (message != null) { 068 if (!continuation.isResumed()) { 069 LOG.debug("Resuming suspended continuation {}", continuation); 070 continuation.setAttribute("undelivered_message", new UndeliveredAjaxMessage(message, consumer)); 071 continuation.resume(); 072 } else { 073 LOG.debug("Message available, but continuation is already resumed. Buffer for next time."); 074 bufferMessageForDelivery(message, consumer); 075 } 076 } 077 } catch (Exception e) { 078 LOG.warn("Error receiving message " + e.getMessage() + ". This exception is ignored.", e); 079 } 080 081 } else if (System.currentTimeMillis() - lastAccess > 2 * this.maximumReadTimeout) { 082 new Thread() { 083 @Override 084 public void run() { 085 LOG.debug("Closing consumers on client: {}", client); 086 client.closeConsumers(); 087 } 088 }.start(); 089 } else { 090 try { 091 Message message = consumer.receive(10); 092 bufferMessageForDelivery(message, consumer); 093 } catch (Exception e) { 094 LOG.warn("Error receiving message " + e.getMessage() + ". This exception is ignored.", e); 095 } 096 } 097 } 098 099 public void bufferMessageForDelivery(Message message, MessageConsumer consumer) { 100 if (message != null) { 101 synchronized (undeliveredMessages) { 102 undeliveredMessages.addLast(new UndeliveredAjaxMessage(message, consumer)); 103 } 104 } 105 } 106}