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ActiveMQ example source code file (CommandMessageListener.java)

This example ActiveMQ source code file (CommandMessageListener.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" TM.

Java - ActiveMQ tags/keywords

commandhandler, commandhandler, commandmessagelistener, exception, exception, factoryfinder, illegalaccessexception, instantiationexception, io, ioexception, message, message, messageproducer, textmessage, textmessage

The ActiveMQ CommandMessageListener.java source code

/**
 * 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.broker.util;

import java.io.IOException;

import javax.jms.Destination;
import javax.jms.JMSException;
import javax.jms.Message;
import javax.jms.MessageListener;
import javax.jms.MessageProducer;
import javax.jms.Session;
import javax.jms.TextMessage;

import org.apache.activemq.command.ActiveMQTextMessage;
import org.apache.activemq.util.FactoryFinder;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

/**
 * 
 */
public class CommandMessageListener implements MessageListener {
    private static final Logger LOG = LoggerFactory.getLogger(CommandMessageListener.class);

    private Session session;
    private MessageProducer producer;
    private CommandHandler handler;

    public CommandMessageListener(Session session) {
        this.session = session;
    }

    public void onMessage(Message message) {
        if (LOG.isDebugEnabled()) {
            LOG.debug("Received command: " + message);
        }
        if (message instanceof TextMessage) {
            TextMessage request = (TextMessage)message;
            try {
                Destination replyTo = message.getJMSReplyTo();
                if (replyTo == null) {
                    LOG.warn("Ignored message as no JMSReplyTo set: " + message);
                    return;
                }
                Message response = processCommand(request);
                addReplyHeaders(request, response);
                getProducer().send(replyTo, response);
            } catch (Exception e) {
                LOG.error("Failed to process message due to: " + e + ". Message: " + message, e);
            }
        } else {
            LOG.warn("Ignoring invalid message: " + message);
        }
    }

    protected void addReplyHeaders(TextMessage request, Message response) throws JMSException {
        String correlationID = request.getJMSCorrelationID();
        if (correlationID != null) {
            response.setJMSCorrelationID(correlationID);
        }
    }

    /**
     * Processes an incoming JMS message returning the response message
     */
    public Message processCommand(TextMessage request) throws Exception {
        TextMessage response = session.createTextMessage();
        getHandler().processCommand(request, response);
        return response;
    }

    /**
     * Processes an incoming command from a console and returning the text to
     * output
     */
    public String processCommandText(String line) throws Exception {
        TextMessage request = new ActiveMQTextMessage();
        request.setText(line);
        TextMessage response = new ActiveMQTextMessage();
        getHandler().processCommand(request, response);
        return response.getText();
    }

    public Session getSession() {
        return session;
    }

    public MessageProducer getProducer() throws JMSException {
        if (producer == null) {
            producer = getSession().createProducer(null);
        }
        return producer;
    }

    public CommandHandler getHandler() throws IllegalAccessException, IOException, InstantiationException, ClassNotFoundException {
        if (handler == null) {
            handler = createHandler();
        }
        return handler;
    }

    private CommandHandler createHandler() throws IllegalAccessException, IOException, ClassNotFoundException, InstantiationException {
        FactoryFinder factoryFinder = new FactoryFinder("META-INF/services/org/apache/activemq/broker/");
        return (CommandHandler)factoryFinder.newInstance("agent");
    }
}

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