/*
*
* 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.qpid.client;
import javax.jms.InvalidDestinationException;
import javax.jms.InvalidSelectorException;
import org.apache.qpid.AMQException;
import org.apache.qpid.AMQInternalException;
import org.apache.qpid.client.filter.JMSSelectorFilter;
import org.apache.qpid.protocol.AMQConstant;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import javax.jms.IllegalStateException;
import javax.jms.JMSException;
import javax.jms.Message;
import javax.jms.Queue;
import javax.jms.QueueBrowser;
import java.util.ArrayList;
import java.util.Enumeration;
import java.util.NoSuchElementException;
import java.util.concurrent.atomic.AtomicBoolean;
public class AMQQueueBrowser implements QueueBrowser
{
private static final Logger _logger = LoggerFactory.getLogger(AMQQueueBrowser.class);
private AtomicBoolean _isClosed = new AtomicBoolean();
private final AMQSession _session;
private final Queue _queue;
private final ArrayList<BasicMessageConsumer> _consumers = new ArrayList<BasicMessageConsumer>();
private final String _messageSelector;
AMQQueueBrowser(AMQSession session, Queue queue, String messageSelector) throws JMSException
{
_session = session;
_queue = queue;
_messageSelector = ((messageSelector == null) || (messageSelector.trim().length() == 0)) ? null : messageSelector;
validateQueue((AMQDestination) queue);
if(_messageSelector != null)
{
validateSelector(_messageSelector);
}
}
private void validateSelector(String messageSelector) throws InvalidSelectorException
{
try
{
new JMSSelectorFilter(messageSelector);
}
catch (AMQInternalException e)
{
throw new InvalidSelectorException(e.getMessage());
}
}
private void validateQueue(AMQDestination queue) throws JMSException
{
try
{
// Essentially just test the connection/session is still active
_session.sync();
// TODO - should really validate queue exists, but we often rely on creating the consumer to create the queue :(
// _session.declareQueuePassive( queue );
}
catch (AMQException e)
{
if(e.getErrorCode() == AMQConstant.NOT_FOUND)
{
throw new InvalidDestinationException(e.getMessage());
}
else
{
final JMSException jmsException = new JMSException(e.getMessage(), String.valueOf(e.getErrorCode().getCode()));
jmsException.setLinkedException(e);
throw jmsException;
}
}
}
public Queue getQueue() throws JMSException
{
checkState();
return _queue;
}
private void checkState() throws JMSException
{
if (_isClosed.get())
{
throw new IllegalStateException("Queue Browser");
}
if (_session.isClosed())
{
throw new IllegalStateException("Session is closed");
}
}
public String getMessageSelector() throws JMSException
{
checkState();
return _messageSelector;
}
public Enumeration getEnumeration() throws JMSException
{
checkState();
if(!_session.getAMQConnection().started())
{
throw new IllegalStateException("Cannot enumerate message on the queue while the Connection is stopped");
}
final BasicMessageConsumer consumer =
(BasicMessageConsumer) _session.createBrowserConsumer(_queue, _messageSelector, false);
_consumers.add(consumer);
return new QueueBrowserEnumeration(consumer);
}
public void close() throws JMSException
{
for (BasicMessageConsumer consumer : _consumers)
{
consumer.close();
}
_consumers.clear();
}
private class QueueBrowserEnumeration implements Enumeration
{
private Message _nextMessage;
private BasicMessageConsumer _consumer;
public QueueBrowserEnumeration(BasicMessageConsumer consumer) throws JMSException
{
if (consumer != null)
{
_consumer = consumer;
prefetchMessage();
}
_logger.debug("QB:created with first element:" + _nextMessage);
}
public boolean hasMoreElements()
{
_logger.debug("QB:hasMoreElements:" + (_nextMessage != null));
return (_nextMessage != null);
}
public Object nextElement()
{
Message msg = _nextMessage;
if (msg == null)
{
throw new NoSuchElementException("No messages") ;
}
try
{
_logger.debug("QB:nextElement about to receive");
prefetchMessage();
_logger.debug("QB:nextElement received:" + _nextMessage);
}
catch (JMSException e)
{
_logger.warn("Exception caught while queue browsing", e);
_nextMessage = null;
try
{
closeConsumer() ;
}
catch (final JMSException jmse) {} // ignore
}
return msg;
}
private void prefetchMessage() throws JMSException
{
_nextMessage = _consumer.receiveBrowse();
if (_nextMessage == null)
{
closeConsumer() ;
}
}
private void closeConsumer() throws JMSException
{
if (_consumer != null)
{
BasicMessageConsumer consumer = _consumer ;
_consumer = null ;
consumer.close() ;
}
}
}
}