src/java/org/apache/jcs/JCS.java

package org.apache.jcs;


/*
 * Copyright 2001-2004 The Apache Software Foundation.
 *
 * 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.
 */


import org.apache.jcs.access.GroupCacheAccess;
import org.apache.jcs.access.exception.CacheException;
import org.apache.jcs.engine.behavior.ICompositeCacheAttributes;
import org.apache.jcs.engine.control.CompositeCache;
import org.apache.jcs.engine.control.CompositeCacheManager;

/**
 * Simple class for using JCS. To use JCS in your application, you can use the
 * static methods of this class to get access objects (instances of this class)
 * for your cache regions. Ideally this class should be all you need to import
 * to use JCS. One JCS should be created for each region you want to access. If
 * you have several regions, then get instances for each. For best performance
 * the getInstance call should be made in an initialization method.
 *
 * @version $Id$
 */
public class JCS extends GroupCacheAccess
{
    private static String configFilename = null;

    private static CompositeCacheManager cacheMgr;

    /**
     * Protected constructor for use by the static factory methods.
     *
     * @param cacheControl Cache which the instance will provide access to
     */
    protected JCS( CompositeCache cacheControl )
    {
        super( cacheControl );
    }

    /**
     * Get a JCS which accesses the provided region.
     *
     * @param region Region that return JCS will provide access to
     * @return A JCS which provides access to a given region.
     * @exception CacheException
     */
    public static JCS getInstance( String region )
        throws CacheException
    {
        ensureCacheManager();

        return new JCS( cacheMgr.getCache( region ) );
    }

    /**
     * Get a JCS which accesses the provided region.
     *
     * @param region Region that return JCS will provide access to
     * @param icca CacheAttributes for region
     * @return A JCS which provides access to a given region.
     * @exception CacheException
     */
    public static JCS getInstance( String region,
                                   ICompositeCacheAttributes icca )
        throws CacheException
    {
        ensureCacheManager();

        return new JCS( cacheMgr.getCache( region, icca ) );
    }

    /**
     * Gets an instance of CompositeCacheManager and stores it in the cacheMgr class
     * field, if it is not already set. Unlike the implementation in
     * CacheAccess, the cache manager is a CompositeCacheManager. NOTE: This can
     * will be moved up into GroupCacheAccess.
     */
    protected static synchronized void ensureCacheManager()
    {
        if ( cacheMgr == null )
        {
            if ( configFilename == null )
            {
                cacheMgr = CompositeCacheManager.getInstance();
            }
            else
            {
                cacheMgr = CompositeCacheManager.getUnconfiguredInstance();

                cacheMgr.configure( configFilename );
            }
        }
    }

    /**
     * Set the filename that the cache manager will be initialized with. Only
     * matters before the instance is initialized.
     * 
     * @param configFilename
     */
    public static void setConfigFilename( String configFilename )
    {
        JCS.configFilename = configFilename;
    }
}