at.ac.tuwien.dsg.cloud.utilities.messaging.lightweight.rabbitMq.channel.ARabbitChannel.java Source code

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Here is the source code for at.ac.tuwien.dsg.cloud.utilities.messaging.lightweight.rabbitMq.channel.ARabbitChannel.java

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/* 
 * Copyright 2015 Svetoslav Videnov <s.videnov@dsg.tuwien.ac.at>.
 *
 * 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 at.ac.tuwien.dsg.cloud.utilities.messaging.lightweight.rabbitMq.channel;

import at.ac.tuwien.dsg.cloud.utilities.messaging.api.Discovery;
import at.ac.tuwien.dsg.cloud.utilities.messaging.api.Shutdownable;
import at.ac.tuwien.dsg.cloud.utilities.messaging.discoveryHelper.DiscoveryException;
import at.ac.tuwien.dsg.cloud.utilities.messaging.lightweight.rabbitMq.RabbitMqFactory;
import at.ac.tuwien.dsg.cloud.utilities.messaging.lightweight.util.Serializer;
import com.rabbitmq.client.Channel;
import com.rabbitmq.client.Connection;
import com.rabbitmq.client.ConnectionFactory;
import java.io.IOException;
import java.util.concurrent.atomic.AtomicBoolean;

/**
 *
 * @author Svetoslav Videnov <s.videnov@dsg.tuwien.ac.at>
 */
public abstract class ARabbitChannel implements Shutdownable {

    protected static final String EXCHANGE_NAME = "comot";

    protected static volatile ConnectionFactory connectionFactory;
    protected static volatile Connection connection;
    protected AtomicBoolean shutdown;
    protected Discovery discovery;
    protected RabbitMqFactory rabbitMqFactory;

    protected Serializer serializer;

    protected ARabbitChannel(Discovery discovery, Serializer serializer, RabbitMqFactory rabbitMqFactory) {
        this.serializer = serializer;
        this.discovery = discovery;
        this.rabbitMqFactory = rabbitMqFactory;
        connectionFactory = rabbitMqFactory.getConnectionFactory();
        this.shutdown = new AtomicBoolean(false);
    }

    protected Channel getChannel() throws ChannelException {
        try {
            synchronized (connectionFactory) {
                if (connection == null) {
                    try {
                        String host = discovery.discoverHost();

                        if (host == null || host.isEmpty()) {
                            throw new ChannelException(String.format("Discovery returned invalid host: %s", host));
                        }

                        connectionFactory.setHost(host);
                        connection = connectionFactory.newConnection();
                    } catch (IOException | DiscoveryException ex) {
                        //we do not reconnect in here do to the fact
                        //that we are discarding messages which are
                        //send during a disconnection phase
                        throw new ChannelException("Exception while connecting to RabbitMQ!", ex);
                    }
                }
            }

            Channel channel = connection.createChannel();
            channel.exchangeDeclare(EXCHANGE_NAME, "topic");
            return channel;
        } catch (IOException ex) {
            //in case we can not create a channel
            //try to establish a new connection
            try {
                //try to close old connection never the less
                connection.close();
            } catch (IOException ex1) {
                //ignore
            }

            connection = null;
            return this.getChannel();
        }
    }

    @Override
    public void shutdown() {
        this.shutdown.set(true);
    }
}