commons-jcs-jcache/src/main/java/org/apache/commons/jcs/jcache/JCSListener.java

/*
 * 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.commons.jcs.jcache;

import javax.cache.configuration.CacheEntryListenerConfiguration;
import javax.cache.configuration.Factory;
import javax.cache.event.CacheEntryCreatedListener;
import javax.cache.event.CacheEntryEvent;
import javax.cache.event.CacheEntryEventFilter;
import javax.cache.event.CacheEntryExpiredListener;
import javax.cache.event.CacheEntryListener;
import javax.cache.event.CacheEntryListenerException;
import javax.cache.event.CacheEntryRemovedListener;
import javax.cache.event.CacheEntryUpdatedListener;
import java.io.Closeable;
import java.util.ArrayList;
import java.util.List;

public class JCSListener<K, V> implements Closeable
{
    private final boolean oldValue;
    private final boolean synchronous;
    private final CacheEntryEventFilter<? super K, ? super V> filter;
    private final CacheEntryListener<? super K, ? super V> delegate;
    private final boolean remove;
    private final boolean expire;
    private final boolean update;
    private final boolean create;

    public JCSListener(final CacheEntryListenerConfiguration<K, V> cacheEntryListenerConfiguration)
    {
        oldValue = cacheEntryListenerConfiguration.isOldValueRequired();
        synchronous = cacheEntryListenerConfiguration.isSynchronous();

        final Factory<CacheEntryEventFilter<? super K, ? super V>> filterFactory = cacheEntryListenerConfiguration
                .getCacheEntryEventFilterFactory();
        if (filterFactory == null)
        {
            filter = NoFilter.INSTANCE;
        }
        else
        {
            filter = filterFactory.create();
        }

        delegate = cacheEntryListenerConfiguration.getCacheEntryListenerFactory().create();
        remove = CacheEntryRemovedListener.class.isInstance(delegate);
        expire = CacheEntryExpiredListener.class.isInstance(delegate);
        update = CacheEntryUpdatedListener.class.isInstance(delegate);
        create = CacheEntryCreatedListener.class.isInstance(delegate);
    }

    public void onRemoved(final List<CacheEntryEvent<? extends K, ? extends V>> events) throws CacheEntryListenerException
    {
        if (remove)
        {
            CacheEntryRemovedListener.class.cast(delegate).onRemoved(filter(events));
        }
    }

    public void onExpired(final List<CacheEntryEvent<? extends K, ? extends V>> events) throws CacheEntryListenerException
    {
        if (expire)
        {
            CacheEntryExpiredListener.class.cast(delegate).onExpired(filter(events));
        }
    }

    public void onUpdated(final List<CacheEntryEvent<? extends K, ? extends V>> events) throws CacheEntryListenerException
    {
        if (update)
        {
            CacheEntryUpdatedListener.class.cast(delegate).onUpdated(filter(events));
        }
    }

    public void onCreated(final List<CacheEntryEvent<? extends K, ? extends V>> events) throws CacheEntryListenerException
    {
        if (create)
        {
            CacheEntryCreatedListener.class.cast(delegate).onCreated(filter(events));
        }
    }

    private Iterable<CacheEntryEvent<? extends K, ? extends V>> filter(final List<CacheEntryEvent<? extends K, ? extends V>> events)
    {
        if (filter == NoFilter.INSTANCE)
        {
            return events;
        }

        final List<CacheEntryEvent<? extends K, ? extends V>> filtered = new ArrayList<CacheEntryEvent<? extends K, ? extends V>>(
                events.size());
        for (final CacheEntryEvent<? extends K, ? extends V> event : events)
        {
            if (filter.evaluate(event))
            {
                filtered.add(event);
            }
        }
        return filtered;
    }

    @Override
    public void close()
    {
        if (Closeable.class.isInstance(delegate)) {
            Closeable.class.cast(delegate);
        }
    }
}