net.sf.ehcache.constructs.blocking
Class UpdatingSelfPopulatingCache

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

All Implemented Interfaces:

java.lang.Cloneable, Ehcache

public class UpdatingSelfPopulatingCache
extends SelfPopulatingCache

A Cache backed cache that creates entries on demand.

Clients of the cache simply call it without needing knowledge of whether the entry exists in the cache, or whether it needs updating before use.

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: UpdatingSelfPopulatingCache.java 575 2008-01-30 07:22:04Z gregluck $

Author:

Greg Luck

Field Summary

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

factory

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

cache, LOCK_NUMBER, locks, timeoutMillis

Constructor Summary

UpdatingSelfPopulatingCache(Ehcache cache, UpdatingCacheEntryFactory factory)
Creates a SelfPopulatingCache.

Method Summary

Element	get(java.lang.Object key) Looks up an object.
void	refresh() This method should not be used.
protected void	update(java.lang.Object key) Element can never be null.

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

refreshElement

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

Constructor Detail

UpdatingSelfPopulatingCache

public UpdatingSelfPopulatingCache(Ehcache cache,
                                   UpdatingCacheEntryFactory factory)
                            throws CacheException

Creates a SelfPopulatingCache.

Throws:

CacheException

Method Detail

get

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

Looks up an object.

If null, it creates it. If not null, it updates it. For performance this method should only be used with UpdatingCacheEntryFactory's

It is expected that gets, which update as part of the get, might take considerable time. Access to the cache cannot be blocked while that is happening. This method is therefore not synchronized. Mutexes are used for thread safety based on key

Specified by:

get in interface Ehcache

Overrides:

get in class SelfPopulatingCache

Parameters:

key -

Returns:

a value

Throws:

CacheException

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)

update

protected void update(java.lang.Object key)

Element can never be null. Add a null guard just in case.

Parameters:

key -

refresh

public void refresh()
             throws CacheException

This method should not be used. Because elements are always updated before they are returned, it makes no sense to refresh this cache.

Overrides:

refresh in class SelfPopulatingCache

Throws:

CacheException