org.dmd.dmp.server.servlet.base.cache

Class CacheListener

java.lang.Object

org.dmd.dmp.server.servlet.base.cache.CacheListener

Direct Known Subclasses:

CacheFullListener, CacheIndexListener

public abstract class CacheListener
extends Object

The CacheListener is a base class for the implementation of listeners for events that are generated by the cache i.e. events that indicate object creation, deletion or modification.

Field Summary

Fields

Modifier and Type	Field and Description
protected CacheRegistration	cacheRegistration

Constructor Summary

Constructors

Modifier	Constructor and Description
protected	CacheListener(CacheRegistration reg, DmpEventHandlerIF eh, org.dmd.dmc.DmcSliceInfo dsi)

Method Summary

Modifier and Type	Method and Description
Collection<org.dmd.dmw.DmwNamedObjectWrapper>	activateAndRetrieve() The activateAndRetrieve method will register the listener with the cache and retrieve the set of objects for which the particular derived class of CacheListener was created.
CacheRegistration	getCacheRegistration()
long	getListenerID()
abstract String	getTraceInfo()
void	processCacheEvent(org.dmd.dmp.server.extended.DMPEvent event) This method is called by the cache when some event has occurred.
SessionIF	session()

Methods inherited from class java.lang.Object

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

Field Detail

cacheRegistration

protected final CacheRegistration cacheRegistration

Constructor Detail

CacheListener

protected CacheListener(CacheRegistration reg,
                        DmpEventHandlerIF eh,
                        org.dmd.dmc.DmcSliceInfo dsi)

Method Detail

getCacheRegistration

public CacheRegistration getCacheRegistration()

Returns:

our cache registration.

getListenerID

public long getListenerID()

session

public SessionIF session()

Returns:

the session associated with this listener.

activateAndRetrieve

public Collection<org.dmd.dmw.DmwNamedObjectWrapper> activateAndRetrieve()

The activateAndRetrieve method will register the listener with the cache and retrieve the set of objects for which the particular derived class of CacheListener was created. By tying these operations together and synchronizing on the cache while the listener is added (and objects returned), we guarantee that we will properly receive events for the set of objects that we're interested in AFTER we have finished sending a set of objects associated with a GetRequest.

This is due to the fact that the GetRequestProcessor (which generally calls this method) is synchronized against itself while the objects that come back from this call are being sent back to the client. If events are generated by the cache while the GetRequestProcessor is still sending back the objects, their forwarding will be blocked until sending of the objects is complete.

No one said that a complex, multi-user web application would be simple ;-)

Returns:

a set of objects from the cache.

processCacheEvent

public void processCacheEvent(org.dmd.dmp.server.extended.DMPEvent event)

This method is called by the cache when some event has occurred. It performs some basic checks and, if the event passes those checks, it calls the abstract handleEvent() method that has to be overloaded by the listener implementation.

Parameters:

event - the event to be processed.

getTraceInfo

public abstract String getTraceInfo()

Returns:

a string containing information that's useful for tracing.