package org.apache.commons.jcs.access;
/*
* 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.
*/
import java.io.IOException;
import org.apache.commons.jcs.access.behavior.ICacheAccessManagement;
import org.apache.commons.jcs.access.exception.CacheException;
import org.apache.commons.jcs.engine.behavior.ICompositeCacheAttributes;
import org.apache.commons.jcs.engine.behavior.IElementAttributes;
import org.apache.commons.jcs.engine.control.CompositeCache;
import org.apache.commons.jcs.engine.stats.behavior.ICacheStats;
/**
* This class provides the common methods for all types of access to the cache.
* <p>
* An instance of this class is tied to a specific cache region. Static methods are provided to get
* such instances.
* <p>
* Using this class you can retrieve an item, the item's wrapper, and the element's configuration. You can also put an
* item in the cache, remove an item, and clear a region.
* <p>
* The JCS class is the preferred way to access these methods.
*/
public abstract class AbstractCacheAccess<K, V>
implements ICacheAccessManagement
{
/**
* The cache that a given instance of this class provides access to.
* <p>
* TODO Should this be the interface?
*/
private final CompositeCache<K, V> cacheControl;
/**
* Constructor for the CacheAccess object.
* <p>
* @param cacheControl The cache which the created instance accesses
*/
protected AbstractCacheAccess( CompositeCache<K, V> cacheControl )
{
this.cacheControl = cacheControl;
}
/**
* Removes all of the elements from a region.
* <p>
* @throws CacheException
*/
@Override
public void clear()
throws CacheException
{
try
{
this.getCacheControl().removeAll();
}
catch ( IOException e )
{
throw new CacheException( e );
}
}
/**
* This method is does not reset the attributes for items already in the cache. It could
* potentially do this for items in memory, and maybe on disk (which would be slow) but not
* remote items. Rather than have unpredictable behavior, this method just sets the default
* attributes. Items subsequently put into the cache will use these defaults if they do not
* specify specific attributes.
* <p>
* @param attr the default attributes.
* @throws CacheException if something goes wrong.
*/
@Override
public void setDefaultElementAttributes( IElementAttributes attr )
throws CacheException
{
this.getCacheControl().setElementAttributes( attr );
}
/**
* Retrieves A COPY OF the default element attributes used by this region. This does not provide
* a reference to the element attributes.
* <p>
* Each time an element is added to the cache without element attributes, the default element
* attributes are cloned.
* <p>
* @return the default element attributes used by this region.
* @throws CacheException
*/
@Override
public IElementAttributes getDefaultElementAttributes()
throws CacheException
{
return this.getCacheControl().getElementAttributes();
}
/**
* This returns the ICacheStats object with information on this region and its auxiliaries.
* <p>
* This data can be formatted as needed.
* <p>
* @return ICacheStats
*/
@Override
public ICacheStats getStatistics()
{
return this.getCacheControl().getStatistics();
}
/**
* @return A String version of the stats.
*/
@Override
public String getStats()
{
return this.getCacheControl().getStats();
}
/**
* Dispose this region. Flushes objects to and closes auxiliary caches. This is a shutdown
* command!
* <p>
* To simply remove all elements from the region use clear().
*/
@Override
public void dispose()
{
this.getCacheControl().dispose();
}
/**
* Gets the ICompositeCacheAttributes of the cache region.
* <p>
* @return ICompositeCacheAttributes, the controllers config info, defined in the top section of
* a region definition.
*/
@Override
public ICompositeCacheAttributes getCacheAttributes()
{
return this.getCacheControl().getCacheAttributes();
}
/**
* Sets the ICompositeCacheAttributes of the cache region.
* <p>
* @param cattr The new ICompositeCacheAttribute value
*/
@Override
public void setCacheAttributes( ICompositeCacheAttributes cattr )
{
this.getCacheControl().setCacheAttributes( cattr );
}
/**
* This instructs the memory cache to remove the <i>numberToFree</i> according to its eviction
* policy. For example, the LRUMemoryCache will remove the <i>numberToFree</i> least recently
* used items. These will be spooled to disk if a disk auxiliary is available.
* <p>
* @param numberToFree
* @return the number that were removed. if you ask to free 5, but there are only 3, you will
* get 3.
* @throws CacheException
*/
@Override
public int freeMemoryElements( int numberToFree )
throws CacheException
{
int numFreed = -1;
try
{
numFreed = this.getCacheControl().getMemoryCache().freeElements( numberToFree );
}
catch ( IOException ioe )
{
String message = "Failure freeing memory elements.";
throw new CacheException( message, ioe );
}
return numFreed;
}
public CompositeCache<K, V> getCacheControl() {
return cacheControl;
}
}