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Date: Mon, 17 Nov 2003 15:31:18 -0600
From: Aaron Smuts <aasmuts@wisc.edu>
Subject: RE: Alter behavior through event handling?
In-reply-to: <FEECCDB72E88F043A05F2909BBFF70E90D4B63@mail4.concurtech.net>
To: 'Turbine JCS Users List' <turbine-jcs-user@jakarta.apache.org>
Message-id: <000001c3ad52$2340f910$20c09792@smuts>
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Importance: Normal

In the cache access class you can get the elementattributes for and
item.  Every item in the cache is given one by default.  If you are
putting something in, you can get the default elementattributes and then
modify it and then use the put method that takes the elementattributes
as an argument.  

To the elmentattributes, you can add something that implements
org.apache.jcs.engine.control.event.behavior.IElementEventHandler

This has only one method.  public Serializable handleElementEvent(
IElementEvent event );

The ElementEvent extends java's event object.  So you can call 

event.getSource()  This will return an object.  Cast it to an
ICacheElement.

You can also find out what the event code is. 

The element events are put in a queue and run in the background.  You
can do whatever you want there.

This should be easy:
Again, implement an IElementEventHandler and add it to the
elementattributes for the item you want.  (You can add more than one
event handler.)  Get the event id and the ICacheElement from the event
object that is passed to the handler's only method, and do whatever you
want there.  It will run in the background.  

Right now only two events are handled by the compositecache, spool to
disk available and unavailable.  I will implement all the events in
IElementEventConstants soon.

> -----Original Message-----
> From: Todd Carmichael [mailto:toddc@concur.com]
> Sent: Monday, November 17, 2003 11:14 AM
> To: 'Turbine JCS Users List'
> Subject: RE: Alter behavior through event handling?
> 
> +1 for event handling.
> +1 For similar changes in Torque so that a JCS event handling
mechanism
> calls into org.apache.torque.manager.CacheListener.  In particular, I
want
> the remote and Lateral caching updates/removes to hook into Torque.
> 
> ToddC
> 
> 
> -----Original Message-----
> From: Sean Cooper [mailto:secooper@vt.edu]
> Sent: Wednesday, September 24, 2003 12:37 PM
> To: turbine-jcs-user@jakarta.apache.org
> Subject: Alter behavior through event handling?
> 
> 
> I have not been able to determine if this is possible, but here is
what I
> am
> trying to do.
> 
> app 1) When something runs its life in the cache, rather then drop
from
> the
> cache entirely, call a method on that particular object to refresh its
> data
> 
> app 2) When something runs its life in the cache, drop it from the
cache,
> and since the item being cached is a java.io.File reference delete the
> file
> from the hard drive  (no, I cannot simple cache the java.io.File
contents
> in
> JCS they aren't truly serializable and need to be streamed/loaded
manually
> to disk)
> 
> I envision achieving this behavior by intercepting a cache release
event
> of
> sorts, but I cannot figure out how to latch on to the event handler to
> process it.  Am I missing something?  Or are the events and event
handlers
> not supposed to be fooled around with?
> 
> -Sean
> 
> 
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