org.directwebremoting.jms.DwrMessageConsumer Maven / Gradle / Ivy

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DWR is easy Ajax for Java. It makes it simple to call Java code directly from Javascript. It gets rid of almost all the boiler plate code between the web browser and your Java code.
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/*
 * Copyright 2005 Joe Walker
 *
 * 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.directwebremoting.jms;

import javax.jms.Destination;
import javax.jms.IllegalStateException;
import javax.jms.JMSException;
import javax.jms.Message;
import javax.jms.MessageConsumer;
import javax.jms.MessageListener;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.directwebremoting.Hub;
import org.directwebremoting.HubFactory;
import org.directwebremoting.ServerContext;
import org.directwebremoting.event.MessageEvent;

/**
 * A {@link MessageConsumer} for DWR
 * @author Joe Walker [joe at getahead dot ltd dot uk]
 */
public class DwrMessageConsumer implements MessageConsumer
{
    /**
     * @see javax.jms.Session#createConsumer(Destination)
     */
    public DwrMessageConsumer(DwrConnection connection, Destination destination) throws JMSException
    {
        this(connection, destination, null, false);
    }

    /**
     * @throws JMSException
     * @see javax.jms.Session#createConsumer(Destination, String)
     */
    public DwrMessageConsumer(DwrConnection connection, Destination destination, String messageSelector) throws JMSException
    {
        this(connection, destination, messageSelector, false);
    }

    /**
     * @see javax.jms.Session#createConsumer(Destination, String, boolean)
     */
    public DwrMessageConsumer(DwrConnection connection, Destination destination, String messageSelector, boolean noLocal) throws JMSException
    {
        this.destination = destination;
        setMessageSelector(messageSelector);
        this.noLocal = noLocal;

        ServerContext serverContext = connection.getServerContext();

        if (serverContext != null)
        {
            hub = HubFactory.get(serverContext);
        }
        else
        {
            hub = HubFactory.get();
        }

        if (destination instanceof DwrTopic)
        {
            DwrTopic topic = (DwrTopic) destination;
            String topicName = topic.getTopicName();

            hub.subscribe(topicName, new MessageListenerMessageListener());
        }
        else
        {
            throw new IllegalStateException("Unsuported Destination type (" + destination.getClass().getCanonicalName() + "). Only Topics are currently supported.");
        }
    }

    /**
     * @author Joe Walker [joe at getahead dot ltd dot uk]
     */
    public final class MessageListenerMessageListener implements org.directwebremoting.event.MessageListener
    {
        public void onMessage(MessageEvent message)
        {
            if (messageListener != null)
            {
                messageListener.onMessage(new DwrMessage(message.getHub(), message));
            }
        }
    }

    /* (non-Javadoc)
     * @see javax.jms.MessageConsumer#close()
     */
    public void close() throws JMSException
    {
    }

    /* (non-Javadoc)
     * @see javax.jms.MessageConsumer#getMessageListener()
     */
    public MessageListener getMessageListener() throws JMSException
    {
        return messageListener;
    }

    /* (non-Javadoc)
     * @see javax.jms.MessageConsumer#setMessageListener(javax.jms.MessageListener)
     */
    public void setMessageListener(MessageListener messageListener) throws JMSException
    {
        this.messageListener = messageListener;
    }

    /**
     * @param messageSelector the messageSelector to set
     */
    public void setMessageSelector(String messageSelector)
    {
        this.messageSelector = messageSelector;

        if (messageSelector != null && messageSelector.length() != 0)
        {
            throw Unsupported.noMessageSelectors();
        }
    }

    /* (non-Javadoc)
     * @see javax.jms.MessageConsumer#getMessageSelector()
     */
    public String getMessageSelector() throws JMSException
    {
        return messageSelector;
    }

    /* (non-Javadoc)
     * @see javax.jms.MessageConsumer#receive()
     */
    public Message receive() throws JMSException
    {
        MessageListener old = getMessageListener();

        BlockingMessageListener listener = new BlockingMessageListener();

        setMessageListener(listener);
        Message message = listener.receive(0);
        setMessageListener(old);

        return message;
    }

    /* (non-Javadoc)
     * @see javax.jms.MessageConsumer#receive(long)
     */
    public Message receive(long timeout) throws JMSException
    {
        MessageListener old = getMessageListener();

        BlockingMessageListener listener = new BlockingMessageListener();

        setMessageListener(listener);
        Message message = listener.receive(timeout);
        setMessageListener(old);

        return message;
    }

    /* (non-Javadoc)
     * @see javax.jms.MessageConsumer#receiveNoWait()
     */
    public Message receiveNoWait() throws JMSException
    {
        log.warn("MessageConsumer.receiveNoWait() probably doesn't do what you need in a queue context");

        MessageListener old = getMessageListener();

        BlockingMessageListener listener = new BlockingMessageListener();

        setMessageListener(listener);
        Message message = listener.receive(1);
        setMessageListener(old);

        return message;
    }

    /**
     * The Hub for this instance of DWR
     */
    protected Hub hub;

    /**
     * A way to filter messages based on message properties
     */
    protected String messageSelector;

    /**
     * The queue or topic that this message is destined for
     */
    protected Destination destination;

    /**
     * Do we get messages that are sent locally?
     */
    protected boolean noLocal;

    /**
     * What we do with inbound messages
     */
    protected MessageListener messageListener;

    /**
     * The log stream
     */
    private static final Log log = LogFactory.getLog(DwrMessageConsumer.class);
}