Package org.apache.geode.cache

Interface CacheListener<K,V>

All Superinterfaces:

CacheCallback, Declarable

All Known Subinterfaces:

RegionMembershipListener<K,V>, RegionRoleListener<K,V>

All Known Implementing Classes:

CacheListenerAdapter, RegionMembershipListenerAdapter, RegionRoleListenerAdapter

public interface CacheListener<K,V>
extends CacheCallback

A listener to handle region or entry related events.

Instead of implementing this interface it is recommended that you extend the CacheListenerAdapter class.

Avoiding the risk of deadlock

The methods on a CacheListener are invoked while holding a lock on the entry described by the EntryEvent, as a result if the listener method takes a long time to execute then it will cause the operation that caused it to be invoked to take a long time. In addition, listener code which calls Region methods could result in a deadlock. For example, in afterUpdate(EntryEvent) for entry key k1, put(k2, someVal) is called at the same time afterUpdate(EntryEvent) for entry key k2 calls put(k1, someVal) a deadlock may result. This co-key dependency example can be extended to a co-Region dependency where listener code in Region "A" performs Region operations on "B" and listener code in Region "B" performs Region operations on "A". Deadlocks may be either java-level or distributed multi-VM dead locks depending on Region configuration. To be assured of no deadlocks, listener code should cause some other thread to access the region and must not wait for that thread to complete the task.

WARNING: To avoid risk of deadlock, do not invoke CacheFactory.getAnyInstance() from within any callback methods. Instead use EntryEvent.getRegion().getCache() or RegionEvent.getRegion().getCache().

Concurrency

Multiple events, on different entries, can cause concurrent invocation of CacheListener methods. Any exceptions thrown by the listener are caught by GemFire and logged.

Declaring instances in Cache XML files

To declare a CacheListener in a Cache XML file, it must also implement Declarable

Since:

GemFire 3.0

See Also:

• AttributesFactory.addCacheListener(org.apache.geode.cache.CacheListener<K, V>)
• AttributesFactory.initCacheListeners(org.apache.geode.cache.CacheListener<K, V>[])
• RegionAttributes.getCacheListeners()
• AttributesMutator.addCacheListener(org.apache.geode.cache.CacheListener<K, V>)
• AttributesMutator.removeCacheListener(org.apache.geode.cache.CacheListener<K, V>)
• AttributesMutator.initCacheListeners(org.apache.geode.cache.CacheListener<K, V>[])

Method Summary

Modifier and Type	Method	Description
void	afterCreate(EntryEvent<K,V> event)	Handles the event of new key being added to a region.
void	afterDestroy(EntryEvent<K,V> event)	Handles the event of an entry being destroyed.
void	afterInvalidate(EntryEvent<K,V> event)	Handles the event of an entry's value being invalidated.
void	afterRegionClear(RegionEvent<K,V> event)	Handles the event of a region being cleared.
void	afterRegionCreate(RegionEvent<K,V> event)	Handles the event of a region being created.
void	afterRegionDestroy(RegionEvent<K,V> event)	Handles the event of a region being destroyed.
void	afterRegionInvalidate(RegionEvent<K,V> event)	Handles the event of a region being invalidated.
void	afterRegionLive(RegionEvent<K,V> event)	Handles the event of a region being live after receiving the marker from the server.
void	afterUpdate(EntryEvent<K,V> event)	Handles the event of an entry's value being modified in a region.

Methods inherited from interface org.apache.geode.cache.CacheCallback

close

Methods inherited from interface org.apache.geode.cache.Declarable

init, initialize

Method Details

afterCreate

void afterCreate(EntryEvent<K,V> event)

Handles the event of new key being added to a region. The entry did not previously exist in this region in the local cache (even with a null value).

Parameters:

event - the EntryEvent

See Also:

• Region.create(Object, Object)
• Region.put(Object, Object)
• Region.get(Object)

afterUpdate

void afterUpdate(EntryEvent<K,V> event)

Handles the event of an entry's value being modified in a region. This entry previously existed in this region in the local cache, but its previous value may have been null.

Parameters:

event - the EntryEvent

See Also:

• Region.put(Object, Object)

afterInvalidate

void afterInvalidate(EntryEvent<K,V> event)

Handles the event of an entry's value being invalidated.

Parameters:

event - the EntryEvent

See Also:

• Region.invalidate(Object)

afterDestroy

void afterDestroy(EntryEvent<K,V> event)

Handles the event of an entry being destroyed.

Parameters:

event - the EntryEvent

See Also:

• Region.destroy(Object)

afterRegionInvalidate

void afterRegionInvalidate(RegionEvent<K,V> event)

Handles the event of a region being invalidated. Events are not invoked for each individual value that is invalidated as a result of the region being invalidated. Each subregion, however, gets its own regionInvalidated event invoked on its listener.

Parameters:

event - the RegionEvent

See Also:

• Region.invalidateRegion()
• Region.localInvalidateRegion()

afterRegionDestroy

void afterRegionDestroy(RegionEvent<K,V> event)

Handles the event of a region being destroyed. Events are not invoked for each individual entry that is destroyed as a result of the region being destroyed. Each subregion, however, gets its own afterRegionDestroyed event invoked on its listener.

Parameters:

event - the RegionEvent

See Also:

• Region.destroyRegion()
• Region.localDestroyRegion()
• Region.close()
• RegionService.close()

afterRegionClear

void afterRegionClear(RegionEvent<K,V> event)

Handles the event of a region being cleared. Events are not invoked for each individual entry that is removed as a result of the region being cleared.

Parameters:

event - the RegionEvent

Since:

GemFire 5.0

See Also:

• Region.clear()

afterRegionCreate

void afterRegionCreate(RegionEvent<K,V> event)

Handles the event of a region being created. Events are invoked for each individual region that is created.

Note that this method is only called for creates done in the local vm. To be notified of creates done in remote vms use RegionMembershipListener.afterRemoteRegionCreate(org.apache.geode.cache.RegionEvent<K, V>).

Parameters:

event - the RegionEvent

Since:

GemFire 5.0

See Also:

• Cache.createRegion(java.lang.String, org.apache.geode.cache.RegionAttributes<K, V>)
• Region.createSubregion(java.lang.String, org.apache.geode.cache.RegionAttributes<SK, SV>)

afterRegionLive

void afterRegionLive(RegionEvent<K,V> event)

Handles the event of a region being live after receiving the marker from the server.

Parameters:

event - the RegionEvent

Since:

GemFire 5.5

See Also:

• Cache.readyForEvents()