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DataNucleus third-party Caching plugin
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/**********************************************************************
Copyright (c) 2005 Andy Jefferson and others. All rights reserved.
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.

Contributors:
    ...
**********************************************************************/
package org.datanucleus.cache.swarmcache;

import java.io.Serializable;
import java.util.Collection;
import java.util.Iterator;

import org.datanucleus.NucleusContext;
import org.datanucleus.cache.AbstractLevel2Cache;
import org.datanucleus.cache.CachedPC;

import net.sf.swarmcache.CacheFactory;
import net.sf.swarmcache.ObjectCache;

/**
 * Simple implementation of a plugin for use of SwarmCache caching product with DataNucleus. 
 * Please refer to SwarmCache for full details 
 * of their product.
 */
public class SwarmCacheLevel2Cache extends AbstractLevel2Cache
{
    private static final long serialVersionUID = -8430359936229487099L;
    /** The cache to use. */
    private final ObjectCache cache;

    /**
     * Constructor.
     * @param nucleusCtx Context
     */
    public SwarmCacheLevel2Cache(NucleusContext nucleusCtx)
    {
        super(nucleusCtx);

        CacheFactory factory = new CacheFactory(null);
        cache = factory.createCache(cacheName);
    }

    /**
     * Method to close the cache when no longer needed. Provides a hook to release resources etc.
     */
    public void close()
    {
        if (clearAtClose)
        {
            evictAll();
        }
    }

    /**
     * Accessor for whether the cache contains the specified id.
     * @see org.datanucleus.cache.Level2Cache#containsOid(java.lang.Object)
     */
    public boolean containsOid(Object oid)
    {
        return (get(oid) != null);
    }

    /**
     * Accessor for an object in the cache.
     * @see org.datanucleus.cache.Level2Cache#get(java.lang.Object)
     */
    public CachedPC get(Object oid)
    {
        if (oid instanceof Serializable)
        {
            return (CachedPC)cache.get((Serializable)oid);
        }
        throw new UnsupportedOperationException("SwarmCache doesnt support use of keys that aren't Serializable");
    }

    /**
     * Accessor for the size of the cache.
     * @see org.datanucleus.cache.Level2Cache#getSize()
     */
    public int getSize()
    {
        throw new UnsupportedOperationException("getSize() method not yet supported by SwarmCache plugin");
    }

    /**
     * Accessor for whether the cache is empty
     * @see org.datanucleus.cache.Level2Cache#isEmpty()
     */
    public boolean isEmpty()
    {
        return getSize() == 0;
    }

    /**
     * Method to add an object to the cache under its id
     * @param oid The identity
     * @param pc The cacheable object
     */
    public CachedPC put(Object oid, CachedPC pc)
    {
        if (oid == null || pc == null)
        {
            return null;
        }

        if (oid instanceof Serializable)
        {
            cache.put((Serializable)oid, pc);
        }
        else
        {
            throw new UnsupportedOperationException("SwarmCache doesnt support use of keys that aren't Serializable");
        }
        return pc;
    }

    /**
     * Evict the parameter instance from the second-level cache.
     * @param oid the object id of the instance to evict.
     */
    public void evict(Object oid)
    {
        if (oid instanceof Serializable)
        {
            cache.clear((Serializable)oid);
        }
        else
        {
            throw new UnsupportedOperationException("SwarmCache doesnt support use of keys that aren't Serializable");
        }
    }

    /**
     * Evict the parameter instances from the second-level cache.
     * All instances in the PersistenceManager's cache are evicted
     * from the second-level cache.
     */
    public void evictAll()
    {
        cache.clearAll();
    }

    /**
     * Evict the parameter instances from the second-level cache.
     * @param pcClass the class of instances to evict
     * @param subclasses if true, evict instances of subclasses also
     */
    public void evictAll(Class pcClass, boolean subclasses)
    {
        throw new UnsupportedOperationException("evict(Class, boolean) method not yet supported by SwarmCache plugin");
    }

    /**
     * Evict the parameter instances from the second-level cache.
     * @param oids the object ids of the instance to evict.
     */
    public void evictAll(Collection oids)
    {
        if (oids == null)
        {
            return;
        }

        Iterator iter = oids.iterator();
        while (iter.hasNext())
        {
            evict(iter.next());
        }
    }

    /**
     * Evict the parameter instances from the second-level cache.
     * @param oids the object ids of the instance to evict.
     */
    public void evictAll(Object[] oids)
    {
        if (oids == null)
        {
            return;
        }

        for (int i=0;i