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N-tier applications and Listeners

Amila Jayatillaka
Greenhorn

Joined: Sep 29, 2006
Posts: 28
Hi,
I need to know somethings about N-tier web applications.
Actually what I need is to know is how context listeners, session listeners work with them(and others too). Like in a N-tier application does it share same context attributes or how sessions work with it etc...
Reason I’m asking this is I got to know that in SCWCD 5 they are asking something similar things like this.
Thanks in advance.

SCJP 1.4, SCMAD 1.0, SCWCD 5.0
Devaka Cooray
ExamLab Creator
Saloon Keeper

Joined: Jul 29, 2008
Posts: 3013
    
  35

Hello Amila, are you talking about about n-tier applications or distributed applications? You question makes good sense if it is about distributed applications.


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Amila Jayatillaka
Greenhorn

Joined: Sep 29, 2006
Posts: 28
Devaka Cooray wrote:Hello Amila, are you talking about about n-tier applications or distributed applications? You question makes good sense if it is about distributed applications.


Yes i'm talking about distributed applications....
Actually I thought that N-Tier is about distributed applications
Devaka Cooray
ExamLab Creator
Saloon Keeper

Joined: Jul 29, 2008
Posts: 3013
    
  35

Well Amila, when your application is deployed on a distributed environment, the session information will transfer remotely to other JVMs in the same environment. In this case, session information should have to be serialized and deserialized in order to pass it as a remote object. Hence you should care about HttpSessionActivationListener an must implement it's sessionDidActive and sessionWillPassivate methods appropriately if it is needed. It is required to do so, if the session stores some connections pooling data / or resources which must be committed and/or closed before serializing them. For the SCWCD exam you are NOT expected to have a deep knowledge about distributed environments. Instead of that, basic understanding about HttpSessionActivationListener is sufficient for the exam. And keep in mind that multi-tier (n-tier) architecture is completely differ than distributed environments.

Devaka.
 
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