net.sf.ehcache.event
Interface CacheEventListener

All Superinterfaces:

java.lang.Cloneable

All Known Subinterfaces:

CacheReplicator

All Known Implementing Classes:

JCacheListenerAdaptor, JGroupsCacheReplicator, RMIAsynchronousCacheReplicator, RMISynchronousCacheReplicator

public interface CacheEventListener
extends java.lang.Cloneable

Allows implementers to register callback methods that will be executed when a cache event occurs. The events include:

1. put Element
2. update Element
3. remove Element
4. evict Element
5. an Element expires, either because timeToLive or timeToIdle has been reached.
6. removeAll, which causes all elements to be cleared from the cache

Callbacks to these methods are synchronous and unsynchronized. It is the responsibility of the implementer to safely handle the potential performance and thread safety issues depending on what their listener is doing.

Cache also has putQuiet and removeQuiet methods which do not notify listeners.

Since:

1.2

Version:

$Id: CacheEventListener.java 519 2007-07-27 07:11:45Z gregluck $

Author:

Greg Luck

See Also:

CacheManagerEventListener

Method Summary

java.lang.Object	clone() Creates a clone of this listener.
void	dispose() Give the listener a chance to cleanup and free resources when no longer needed
void	notifyElementEvicted(Ehcache cache, Element element) Called immediately after an element is evicted from the cache.
void	notifyElementExpired(Ehcache cache, Element element) Called immediately after an element is found to be expired.
void	notifyElementPut(Ehcache cache, Element element) Called immediately after an element has been put into the cache.
void	notifyElementRemoved(Ehcache cache, Element element) Called immediately after an attempt to remove an element.
void	notifyElementUpdated(Ehcache cache, Element element) Called immediately after an element has been put into the cache and the element already existed in the cache.
void	notifyRemoveAll(Ehcache cache) Called during Ehcache.removeAll() to indicate that the all elements have been removed from the cache in a bulk operation.

Method Detail

notifyElementRemoved

void notifyElementRemoved(Ehcache cache,
                          Element element)
                          throws CacheException

Called immediately after an attempt to remove an element. The remove method will block until this method returns.

This notification is received regardless of whether the cache had an element matching the removal key or not. If an element was removed, the element is passed to this method, otherwise a synthetic element, with only the key set is passed in.

This notification is not called for the following special cases:

1. removeAll was called. See notifyRemoveAll(net.sf.ehcache.Ehcache)
2. An element was evicted from the cache. See notifyElementEvicted(net.sf.ehcache.Ehcache, net.sf.ehcache.Element)

Parameters:

cache - the cache emitting the notification

element - the element just deleted, or a synthetic element with just the key set if no element was removed.

Throws:

CacheException

notifyElementPut

void notifyElementPut(Ehcache cache,
                      Element element)
                      throws CacheException

Called immediately after an element has been put into the cache. The Cache.put(net.sf.ehcache.Element) method will block until this method returns.

Implementers may wish to have access to the Element's fields, including value, so the element is provided. Implementers should be careful not to modify the element. The effect of any modifications is undefined.

Parameters:

cache - the cache emitting the notification

element - the element which was just put into the cache.

Throws:

CacheException

notifyElementUpdated

void notifyElementUpdated(Ehcache cache,
                          Element element)
                          throws CacheException

Called immediately after an element has been put into the cache and the element already existed in the cache. This is thus an update.

The Cache.put(net.sf.ehcache.Element) method will block until this method returns.

Implementers may wish to have access to the Element's fields, including value, so the element is provided. Implementers should be careful not to modify the element. The effect of any modifications is undefined.

Parameters:

cache - the cache emitting the notification

element - the element which was just put into the cache.

Throws:

CacheException

notifyElementExpired

void notifyElementExpired(Ehcache cache,
                          Element element)

Called immediately after an element is found to be expired. The Cache.remove(Object) method will block until this method returns.

As the Element has been expired, only what was the key of the element is known.

Elements are checked for expiry in ehcache at the following times:

• When a get request is made
• When an element is spooled to the diskStore in accordance with a MemoryStore eviction policy
• In the DiskStore when the expiry thread runs, which by default is Cache.DEFAULT_EXPIRY_THREAD_INTERVAL_SECONDS

If an element is found to be expired, it is deleted and this method is notified.

Parameters:

cache - the cache emitting the notification

element - the element that has just expired

Deadlock Warning: expiry will often come from the DiskStore expiry thread. It holds a lock to the DiskStorea the time the notification is sent. If the implementation of this method calls into a synchronized Cache method and that subsequently calls into DiskStore a deadlock will result. Accordingly implementers of this method should not call back into Cache.

notifyElementEvicted

void notifyElementEvicted(Ehcache cache,
                          Element element)

Called immediately after an element is evicted from the cache. Evicted in this sense means evicted from one store and not moved to another, so that it exists nowhere in the local cache.

In a sense the Element has been removed from the cache, but it is different, thus the separate notification.

Parameters:

cache - the cache emitting the notification

element - the element that has just been evicted

notifyRemoveAll

void notifyRemoveAll(Ehcache cache)

Called during Ehcache.removeAll() to indicate that the all elements have been removed from the cache in a bulk operation. The usual notifyElementRemoved(net.sf.ehcache.Ehcache, net.sf.ehcache.Element) is not called.

This notification exists because clearing a cache is a special case. It is often not practical to serially process notifications where potentially millions of elements have been bulk deleted.

Parameters:

cache - the cache emitting the notification

dispose

void dispose()

Give the listener a chance to cleanup and free resources when no longer needed

clone

java.lang.Object clone()
                       throws java.lang.CloneNotSupportedException

Creates a clone of this listener. This method will only be called by ehcache before a cache is initialized.

This may not be possible for listeners after they have been initialized. Implementations should throw CloneNotSupportedException if they do not support clone.

Returns:

a clone

Throws:

java.lang.CloneNotSupportedException - if the listener could not be cloned.