org.grycap.gpf4med.event.EventBusHandler.java Source code

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Here is the source code for org.grycap.gpf4med.event.EventBusHandler.java

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/*
 * Copyright 2013 Institute for Molecular Imaging Instrumentation (I3M)
 * 
 * Licensed under the EUPL, Version 1.1 or - as soon they will be approved by 
 * the European Commission - subsequent versions of the EUPL (the "Licence");
 * You may not use this work except in compliance with the Licence.
 * You may obtain a copy of the Licence at:
 * 
 *   http://ec.europa.eu/idabc/eupl
 * 
 * Unless required by applicable law or agreed to in writing, software 
 * distributed under the Licence is distributed on an "AS IS" basis,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the Licence for the specific language governing permissions and 
 * limitations under the Licence.
 * 
 * This product combines work with different licenses. See the "NOTICE" text
 * file for details on the various modules and licenses.
 * The "NOTICE" text file is part of the distribution. Any derivative works
 * that you distribute must include a readable copy of the "NOTICE" text file.
 */

package org.grycap.gpf4med.event;

import static com.google.common.base.Preconditions.*;

import java.io.IOException;
import java.net.URL;
import java.util.Collection;
import java.util.Deque;

import javax.annotation.Nullable;

import org.grycap.gpf4med.Closeable2;

import com.google.common.collect.Queues;
import com.google.common.eventbus.EventBus;

public enum EventBusHandler implements Closeable2 {

    INSTANCE;

    public static final String EVENT_BUS_NAME = "dicom-graph-store";

    private final Deque<Object> deque = Queues.synchronizedDeque(Queues.<Object>newArrayDeque());

    private final EventBus eventBus;

    private EventBusHandler() {
        eventBus = new EventBus(EVENT_BUS_NAME);
        // register dead event listener
        register(DeadEventListener.INSTANCE);
    }

    public void register(final Object object) {
        checkArgument(object != null, "Uninitialized subscriber");
        eventBus.register(object);
        deque.push(object);
    }

    public void unregister(final Object object) {
        checkArgument(object != null, "Uninitialized subscriber");
        final boolean contains = deque.remove(object);
        if (contains) {
            try {
                eventBus.unregister(object);
            } catch (Exception e) {
            }
        }
    }

    public void post(final BaseEvent event) {
        checkArgument(event != null, "Uninitialized event");
        eventBus.post(event);
    }

    @Override
    public void setup(final @Nullable Collection<URL> urls) {
        // nothing to do
    }

    @Override
    public void preload() {
        // nothing to do
    }

    @Override
    public void close() throws IOException {
        while (!deque.isEmpty()) {
            final Object object = deque.pop();
            try {
                eventBus.unregister(object);
            } catch (Exception e) {
            }
        }
    }

}