HazelcastLightweightTopic.java

/*
 * #%L
 * Nazgul Project: nazgul-core-cache-impl-hazelcast
 * %%
 * Copyright (C) 2010 - 2017 jGuru Europe AB
 * %%
 * Licensed under the jGuru Europe AB license (the "License"), based
 * on Apache License, Version 2.0; you may not use this file except
 * in compliance with the License.
 *
 * You may obtain a copy of the License at
 *
 *      http://www.jguru.se/licenses/jguruCorporateSourceLicense-2.0.txt
 *
 * 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.
 * #L%
 *
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package se.jguru.nazgul.core.cache.impl.hazelcast;

import com.hazelcast.core.ITopic;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import se.jguru.nazgul.core.cache.api.distributed.async.LightweightTopic;
import se.jguru.nazgul.core.cache.api.distributed.async.LightweightTopicListener;

import java.io.Serializable;
import java.util.Map;
import java.util.TreeMap;

/**
 * LightweightTopic implementation for Hazelcast.
 *
 * @author <a href="mailto:lj@jguru.se">Lennart Jörelid</a>, jGuru Europe AB
 */
public class HazelcastLightweightTopic<MessageType extends Serializable> implements LightweightTopic<MessageType> {

    // Our log
    private static final Logger log = LoggerFactory.getLogger(HazelcastLightweightTopic.class);

    // Internal state
    private final Object lock = new Object();
    private ITopic<MessageType> hazelcastTopic;
    private Map<String, HazelcastLightweightTopicListenerAdapter<MessageType>> knownListeners;

    /**
     * Creates a new HazelcastLightweightTopic (LightweightTopic wrapper), delegating its calls to the provided ITopic
     * instance.
     *
     * @param hazelcastTopic The ITopic received from Hazelcast.
     */
    public HazelcastLightweightTopic(final ITopic<MessageType> hazelcastTopic) {

        this.hazelcastTopic = hazelcastTopic;
        knownListeners = new TreeMap<String, HazelcastLightweightTopicListenerAdapter<MessageType>>();
    }

    /**
     * Sends/Publishes the provided message through this LightweightTopic.
     *
     * @param message The message to publish in this Topic.
     */
    @Override
    public void publish(final MessageType message) {
        hazelcastTopic.publish(message);
    }

    /**
     * Adds a new LightweightTopicListener to this Topic. The LightweightTopicListener is invoked whenever a message is
     * sent through this LightweightTopic.
     *
     * @param listener The LightweightTopicListener to register to this Topic.
     */
    @Override
    public void addListener(final LightweightTopicListener<MessageType> listener) {

        synchronized (lock) {
            final HazelcastLightweightTopicListenerAdapter<MessageType> lst =
                    new HazelcastLightweightTopicListenerAdapter<MessageType>(listener);

            // Add to map and topic
            knownListeners.put(lst.getClusterId(), lst);
            hazelcastTopic.addMessageListener(lst);
        }
    }

    /**
     * Removes the provided LightweightTopicListener from this LightweightTopic.
     *
     * @param listener The listener to remove.
     */
    @Override
    public void removeListener(final LightweightTopicListener<MessageType> listener) {

        // Check sanity.
        if (listener == null) {
            throw new IllegalArgumentException("Cannot handle null listener argument.");
        }

        // Get the Wrapper
        final HazelcastLightweightTopicListenerAdapter<MessageType> toRemove = knownListeners.get(listener.getClusterId());

        if (toRemove == null) {
            log.warn("HazelcastLightweightTopicListenerAdapter [" + listener.getClusterId() + "] not found. Aborting.");
            return;
        }

        synchronized (lock) {
            final String clusterId = listener.getClusterId();
            knownListeners.remove(clusterId);
            hazelcastTopic.removeMessageListener(clusterId);
        }
    }

    /**
     * @return a human-readable, cluster-unique Identifier for this instance.
     */
    @Override
    public String getClusterId() {
        return hazelcastTopic.getName();
    }
}