net.sf.ehcache.constructs.blocking
Class SelfPopulatingCache

java.lang.Object
  net.sf.ehcache.constructs.blocking.BlockingCache
      net.sf.ehcache.constructs.blocking.SelfPopulatingCache

All Implemented Interfaces:

java.lang.Cloneable, Ehcache

Direct Known Subclasses:

UpdatingSelfPopulatingCache

public class SelfPopulatingCache
extends BlockingCache

A selfpopulating decorator for Ehcache that creates entries on demand.

Clients of the cache simply call it without needing knowledge of whether the entry exists in the cache.

The cache is designed to be refreshed. Refreshes operate on the backing cache, and do not degrade performance of BlockingCache.get(java.io.Serializable) calls.

Thread safety depends on the factory being used. The UpdatingCacheEntryFactory should be made thread safe. In addition users of returned values should not modify their contents.

Version:

$Id: SelfPopulatingCache.java 563 2007-11-23 22:07:38Z gregluck $

Author:

Greg Luck

Field Summary

protected CacheEntryFactory

factory A factory for creating entries, given a key

Fields inherited from class net.sf.ehcache.constructs.blocking.BlockingCache

cache, LOCK_NUMBER, locks, timeoutMillis

Constructor Summary

SelfPopulatingCache(Ehcache cache, CacheEntryFactory factory)
Creates a SelfPopulatingCache.

Method Summary

Element	get(java.lang.Object key) Looks up an entry.
void	refresh() Refresh the elements of this cache.
protected void	refreshElement(Element element, Ehcache backingCache) Refresh a single element.

Methods inherited from class net.sf.ehcache.constructs.blocking.BlockingCache

bootstrap, calculateInMemorySize, clearStatistics, clone, dispose, evictExpiredElements, flush, get, getAllWithLoader, getAverageGetTime, getBootstrapCacheLoader, getCache, getCacheConfiguration, getCacheEventNotificationService, getCacheExceptionHandler, getCacheLoader, getCacheManager, getDiskExpiryThreadIntervalSeconds, getDiskStoreSize, getGuid, getKeys, getKeysNoDuplicateCheck, getKeysWithExpiryCheck, getLockForKey, getMaxElementsInMemory, getMaxElementsOnDisk, getMemoryStoreEvictionPolicy, getMemoryStoreSize, getName, getQuiet, getQuiet, getSize, getStatistics, getStatisticsAccuracy, getStatus, getTimeoutMillis, getTimeToIdleSeconds, getTimeToLiveSeconds, getWithLoader, initialise, isDisabled, isDiskPersistent, isElementInMemory, isElementInMemory, isElementOnDisk, isElementOnDisk, isEternal, isExpired, isKeyInCache, isOverflowToDisk, isValueInCache, liveness, load, loadAll, put, put, putQuiet, registerCacheExtension, remove, remove, remove, remove, removeAll, removeAll, removeQuiet, removeQuiet, setBootstrapCacheLoader, setCacheExceptionHandler, setCacheLoader, setCacheManager, setDisabled, setDiskStorePath, setName, setStatisticsAccuracy, setTimeoutMillis, unregisterCacheExtension

Methods inherited from class java.lang.Object

equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Methods inherited from interface net.sf.ehcache.Ehcache

toString

Field Detail

factory

protected final CacheEntryFactory factory

A factory for creating entries, given a key

Constructor Detail

SelfPopulatingCache

public SelfPopulatingCache(Ehcache cache,
                           CacheEntryFactory factory)
                    throws CacheException

Creates a SelfPopulatingCache.

Throws:

CacheException

Method Detail

get

public Element get(java.lang.Object key)
            throws LockTimeoutException

Looks up an entry. creating it if not found.

Specified by:

get in interface Ehcache

Overrides:

get in class BlockingCache

Parameters:

key - an Object value

Returns:

the element, or null, if it does not exist.

Throws:

LockTimeoutException - if timeout millis is non zero and this method has been unable to acquire a lock in that time

See Also:

Ehcache.isExpired(net.sf.ehcache.Element)

refresh

public void refresh()
             throws CacheException

Refresh the elements of this cache.

Refreshes bypass the BlockingCache and act directly on the backing Ehcache. This way, BlockingCache gets can continue to return stale data while the refresh, which might be expensive, takes place.

Quiet methods are used, so that statistics are not affected.

Configure ehcache.xml to stop elements from being refreshed forever:

• use timeToIdle to discard elements unused for a period of time
• use timeToLive to discard elmeents that have existed beyond their allotted lifespan

Throws:

CacheException

refreshElement

protected void refreshElement(Element element,
                              Ehcache backingCache)
                       throws java.lang.Exception

Refresh a single element.

Parameters:

element - the Element to refresh

backingCache - the underlying Ehcache.

Throws:

java.lang.Exception