spring-cache-providers/spring-cache-ehcache/src/main/java/org/apache/archiva/redback/components/cache/ehcache/EhcacheCache.java

package org.apache.archiva.redback.components.cache.ehcache;

/*
 * 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 net.sf.ehcache.Cache;
import net.sf.ehcache.CacheManager;
import net.sf.ehcache.Element;
import net.sf.ehcache.Status;
import net.sf.ehcache.store.MemoryStoreEvictionPolicy;
import org.apache.archiva.redback.components.cache.CacheStatistics;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import javax.annotation.PostConstruct;

/**
 * EhcacheCache 
 * configuration document  available <a href="http://ehcache.sourceforge.net/EhcacheUserGuide.html>EhcacheUserGuide</a>
 *  
 * @author <a href="mailto:joakim@erdfelt.com">Joakim Erdfelt</a>
 *
 * 
 */
public class EhcacheCache
    implements org.apache.archiva.redback.components.cache.Cache
{
    
    private Logger log = LoggerFactory.getLogger( getClass() );    
    
    class Stats
        implements CacheStatistics
    {
        public void clear()
        {
            ehcache.clearStatistics();
        }

        public double getCacheHitRate()
        {
            double hits = getCacheHits();
            double miss = getCacheMiss();

            if ( ( hits == 0 ) && ( hits == 0 ) )
            {
                return 0.0;
            }

            return (double) hits / (double) ( hits + miss );
        }

        public long getCacheHits()
        {
            return ehcache.getStatistics().getCacheHits();
        }

        public long getCacheMiss()
        {
            return ehcache.getStatistics().getCacheMisses();
        }

        public long getSize()
        {
            return ehcache.getMemoryStoreSize() + ehcache.getDiskStoreSize();
        }

    }

    /**
     * how often to run the disk store expiry thread. A large number of 120 seconds plus is recommended
     * 
     */
    private long diskExpiryThreadIntervalSeconds = 600;

    /**
     * Whether to persist the cache to disk between JVM restarts.
     * 
     */
    private boolean diskPersistent = true;

    /**
     * Location on disk for the ehcache store.
     * 
     */
    private String diskStorePath = System.getProperty( "java.io.tmpdir" ) + "/ehcache";

    /**
     *
     */
    private boolean eternal = false;

    /**
     *
     */
    private int maxElementsInMemory = 1000;

    /**
     *
     */
    private String memoryEvictionPolicy = "LRU";

    /**
     *
     */
    private String name = "cache";

    /**
     * Flag indicating when to use the disk store.
     * 
     */
    private boolean overflowToDisk = false;

    /**
     *
     */
    private int timeToIdleSeconds = 600;

    /**
     *
     */
    private int timeToLiveSeconds = 300;
    
    /**
     *
     */    
    private boolean failOnDuplicateCache = false;

    private boolean statisticsEnabled = true;

    private CacheManager cacheManager = CacheManager.getInstance();

    private net.sf.ehcache.Cache ehcache;

    private Stats stats;

    public void clear()
    {
        ehcache.removeAll();
        stats.clear();
    }

    @PostConstruct
    public void initialize()
    {
        stats = new Stats();

        boolean cacheExists = cacheManager.cacheExists( getName() );

        if ( cacheExists )
        {
            if ( failOnDuplicateCache )
            {
                throw new RuntimeException( "A previous cache with name [" + getName() + "] exists." );
            }
            else
            {
                log.warn( "skip duplicate cache " + getName() );
                ehcache = cacheManager.getCache( getName() );
            }
        }

        if (!cacheExists)
        {
            ehcache = new Cache( getName(), getMaxElementsInMemory(), getMemoryStoreEvictionPolicy(), isOverflowToDisk(),
                                 getDiskStorePath(), isEternal(), getTimeToLiveSeconds(), getTimeToIdleSeconds(),
                                 isDiskPersistent(), getDiskExpiryThreadIntervalSeconds(), null );


            cacheManager.addCache( ehcache );
            ehcache.setStatisticsEnabled( statisticsEnabled );
        }
    }    

    public void dispose()
    {
        if ( cacheManager.getStatus().equals( Status.STATUS_ALIVE ) )
        {
            log.info( "Disposing cache: " + ehcache );
            if ( this.ehcache != null )
            {
                cacheManager.removeCache( this.ehcache.getName() );
                ehcache = null;
            }
        }
        else
        {
            log.debug( "Not disposing cache, because cacheManager is not alive: " + ehcache );
        }
    }

    public Object get( Object key )
    {
        if (key == null)
        {
            return null;
        }
        Element elem = ehcache.get( key );
        if ( elem == null )
        {
            return null;
        }
        return elem.getObjectValue();
    }

    public long getDiskExpiryThreadIntervalSeconds()
    {
        return diskExpiryThreadIntervalSeconds;
    }

    public String getDiskStorePath()
    {
        return diskStorePath;
    }

    public int getMaxElementsInMemory()
    {
        return maxElementsInMemory;
    }

    public String getMemoryEvictionPolicy()
    {
        return memoryEvictionPolicy;
    }

    public MemoryStoreEvictionPolicy getMemoryStoreEvictionPolicy()
    {
        return MemoryStoreEvictionPolicy.fromString( memoryEvictionPolicy );
    }

    public String getName()
    {
        return name;
    }

    public CacheStatistics getStatistics()
    {
        return stats;
    }

    public int getTimeToIdleSeconds()
    {
        return timeToIdleSeconds;
    }

    public int getTimeToLiveSeconds()
    {
        return timeToLiveSeconds;
    }

    public boolean hasKey( Object key )
    {
        return ehcache.isKeyInCache( key );
    }

    public boolean isDiskPersistent()
    {
        return diskPersistent;
    }

    public boolean isEternal()
    {
        return eternal;
    }

    public boolean isOverflowToDisk()
    {
        return overflowToDisk;
    }

    public void register( Object key, Object value )
    {
        ehcache.put( new Element( key, value ) );
    }
    
    public Object put( Object key, Object value )
    {
        // Multiple steps done to satisfy Cache API requirement for Previous object return.
        Element elem = null;
        Object previous = null;
        elem = ehcache.get( key );
        if ( elem != null )
        {
            previous = elem.getObjectValue();
        }
        elem = new Element( key, value );
        ehcache.put( elem );
        return previous;
    }

    public Object remove( Object key )
    {
        Element elem = null;
        Object previous = null;
        elem = ehcache.get( key );
        if ( elem != null )
        {
            previous = elem.getObjectValue();
            ehcache.remove( key );
        }

        return previous;
    }

    public void setDiskExpiryThreadIntervalSeconds( long diskExpiryThreadIntervalSeconds )
    {
        this.diskExpiryThreadIntervalSeconds = diskExpiryThreadIntervalSeconds;
    }

    public void setDiskPersistent( boolean diskPersistent )
    {
        this.diskPersistent = diskPersistent;
    }

    public void setDiskStorePath( String diskStorePath )
    {
        this.diskStorePath = diskStorePath;
    }

    public void setEternal( boolean eternal )
    {
        this.eternal = eternal;
    }

    public void setMaxElementsInMemory( int maxElementsInMemory )
    {
        this.maxElementsInMemory = maxElementsInMemory;
    }

    public void setMemoryEvictionPolicy( String memoryEvictionPolicy )
    {
        this.memoryEvictionPolicy = memoryEvictionPolicy;
    }

    public void setName( String name )
    {
        this.name = name;
    }

    public void setOverflowToDisk( boolean overflowToDisk )
    {
        this.overflowToDisk = overflowToDisk;
    }

    public void setTimeToIdleSeconds( int timeToIdleSeconds )
    {
        this.timeToIdleSeconds = timeToIdleSeconds;
    }

    public void setTimeToLiveSeconds( int timeToLiveSeconds )
    {
        this.timeToLiveSeconds = timeToLiveSeconds;
    }

    public boolean isStatisticsEnabled()
    {
        return statisticsEnabled;
    }

    public void setStatisticsEnabled( boolean statisticsEnabled )
    {
        this.statisticsEnabled = statisticsEnabled;
    }

    public boolean isFailOnDuplicateCache()
    {
        return failOnDuplicateCache;
    }

    public void setFailOnDuplicateCache( boolean failOnDuplicateCache )
    {
        this.failOnDuplicateCache = failOnDuplicateCache;
    }
}