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

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Here is the source code for at.ac.tuwien.dsg.cloud.utilities.messaging.lightweight.rabbitMq.channel.ReceivingChannel.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.lightweight.rabbitMq.RabbitMqFactory;
import at.ac.tuwien.dsg.cloud.utilities.messaging.lightweight.rabbitMq.RabbitMqMessage;
import at.ac.tuwien.dsg.cloud.utilities.messaging.lightweight.util.Serializer;
import com.rabbitmq.client.Channel;
import com.rabbitmq.client.ConsumerCancelledException;
import com.rabbitmq.client.QueueingConsumer;
import com.rabbitmq.client.ShutdownSignalException;
import java.io.IOException;
import java.util.ArrayList;
import java.util.List;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

/**
 *
 * @author Svetoslav Videnov <s.videnov@dsg.tuwien.ac.at>
 */
public class ReceivingChannel extends ARabbitChannel {

    private static Logger logger = LoggerFactory.getLogger(ReceivingChannel.class);

    private String queueName;
    private QueueingConsumer consumer;
    private List<String> types;

    public ReceivingChannel(Discovery discovery, Serializer serializer, RabbitMqFactory rabbitMqFactory) {
        super(discovery, serializer, rabbitMqFactory);
        this.types = new ArrayList<>();
    }

    private void reconnect() {
        if (shutdown.get()) {
            return;
        }

        try {
            Thread.sleep(1000);
        } catch (InterruptedException ex) {
            return;
        }

        this.queueName = null;
        try {
            Channel channel = this.getChannel();

            this.queueName = channel.queueDeclare().getQueue();
            this.consumer = this.rabbitMqFactory.getQueueingConsumer(channel);
            channel.basicConsume(queueName, true, consumer);

            synchronized (types) {
                for (String type : types) {
                    this.internalBindType(type);
                }
            }
        } catch (ChannelException | IOException | IllegalStateException ex) {
            this.reconnect();
        }
    }

    private void internalBindType(String type) throws IllegalStateException {
        try {
            this.consumer.getChannel().queueBind(queueName, ARabbitChannel.EXCHANGE_NAME, type);
        } catch (IOException ex) {
            throw new IllegalStateException(ex);
        }
    }

    public void bindType(String type) throws IllegalStateException {
        synchronized (types) {
            this.types.add(type);
        }

        if (this.queueName == null) {
            return;
        }

        this.internalBindType(type);
    }

    public RabbitMqMessage getDelivery() {
        if (this.shutdown.get()) {
            return null;
        }

        //this ensures that we start listening for incoming messages
        //when there is really someone who is interested in listening
        //this way we ensure a lazy startup
        if (this.queueName == null) {
            this.reconnect();
        }

        try {
            QueueingConsumer.Delivery delivery = consumer.nextDelivery();
            return this.serializer.deserilize(delivery.getBody(), RabbitMqMessage.class);
        } catch (IOException | InterruptedException | ShutdownSignalException | ConsumerCancelledException ex) {
            logger.warn("Error while receiving message!", ex);
            this.reconnect();
        }

        return this.getDelivery();
    }
}