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sankha das

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since Nov 02, 2004
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Recent posts by sankha das

Ray,
Joseph was right in saying jsp's reside in the web/presentation tier. For web-client, yes the browser is the client. For the TA's, you can represent the client tier with a desktop sorta system. You can rightly depict its controller and the Business Delegate in the presentation tier and everything else fits in place. Service Locators could be either Web-tier ServiceLocator or EJB tier ServiceLocator depending on the service and your caching requirements. DTO's will obviously be a part of the business tier. Hope that helps.

Thanks
Sankha Subhra Das
Prakash,
from a testers perspective, you need to design, automate and test both applications in Java as well as web applications. Testing on java is a bit easier than other OOP language with the inbuilt functionality most testing tools imbibe. But assuming regression testing, you need to test out apps/web apps in 3 major vendor products like Silk, Winrunner and Robot.

Hope that helps
Sankha Subhra Das
Bee,
yes following Cade, class diagram will tend to deviate from whats done in real life. None of those entities you've mentioned goes into a class diagram as all these are j2ee specific and needs to be entered in component diagram only. Class diagram should be only an extension(NOT MODIFICATION) of the BDM as far as the architecture exam goes. At the most, you can depict some workflow related components like TransactionWorkflowProcessor or FrequentFlyerProcessor etc and you can include a comment saying they'd be depited as SLSB in the design.
Hope that helps.

Thanks
Sankha Subhra Das
Mark,
you can assume maintenance of DB operations, cleaning of cancelled flights and tuning as being present but not depicted in the current architecture. These processes are off the shelf offline operations and manually done by the DBA based on respective airline policies.

Thanks
Sankha Subhra Das
Matthew,
the answer is you May or May not. You can depict Login and Create profile as a seperate Sequence Diagram or can add it with a Main Flow sequence diagram. You can also depict them as comments in the Main Flow sequence diagram as a "pre-condition" or "post-condition". Comments within a sequence diagram could include
After being logged user performs .........
or
If user has awards travel card, user proceeds to pay using it.....

Thanks
Sankha Subhra Das
Peter,
well I did not see such questions appear in my exam. But it won't harm knowing them anyway.


Thanks
Sankha Subhra Das
Joseph,
you are absolutely right when you say SFSB is not apt for clustered environment. I dont wanna point the pitfalls of SFSB here but you can refer the article by Tyler Jewell wherein he discusses the true purpose of SFSBs, where they belong in a J2EE design, and the situations where they should not be used. http://www.onjava.com/pub/a/onjava/2001/10/02/ejb.html

Yes you can achieve load balancing either from your DB or Web/Application Container. The mere fact the Sun prefers to see use of SFSB's should not bias your design choice.

When it comes down to the debate between servlet session and stateful session bean, the servlet session wins out in my mind, except for one point that people always resort to: If you store conversational state in your
HTTPSession then you can't reuse your EJB's for other types of clients.
Very Very true indeed. So herein you hafta think about your TA's. How are they gonna maintain their sessions ?

Sun's choice of hardware gives us a hint trying to identify where the "most appropriate" place for your conversational state should be located. I'm not arguing for completely server side or client side, rather, the state should be located at the tier that does transactional or request demarcation.

For web applications, HttpSession is often enough. If you want the benefits of a SFSB, you can go ahead and design the same. However, all depends on what and how much of session data you wanna store at client. In my design, I have used session data to store only navigational and user preference data. This makes things simple and save increased memory requirements on the server through use of SFSB. I could have gone ahead and added another DB component to synchronise the session state in web tier from time to time. Maybe I left it for next version of the design. Only pitfall, disconnected client will need to restart the booking process all over again but for a 3 page site(login, search and booking), it won't necessarily turn off users.
So bottomline, go ahead and design you think would be necessary to support all requirements and point the design choice(among alternatives obviously) in your assumptions section.

Thanks
Sankha Subhra Das
Anton,
It all depends on your personal interest. I personally feel its all about how curious you would be to design from business reqs vis-a-vis code from detailed designs. Both the roles are supplementary and NOT mutually exclusive.
You would need to have some experience producing class diagrams, component diagrams etc for the exam. If you're a J2EE Developer producing classes/frameworks from technical specs or tech specs from business reqs, you should opt for scea exam. Part1 is generic and a focussed study for few months will see you through.

Thanks
Sankha Subhra Das
Dhiren,
thats precisely what I did for my design. I could leverage the benefit of local interfaces for TA's as and when appropriate and as you pointed out higher performance. And yes its definitely acceptable as long as you support the design well. Part III would test the same performance and session handling aspects and hence you hafta re-justify your design there as well.

Thanks
Sankha Subhra Das
Matthew,
there are two options actually. After saving the images in a local folder, select all, right click and send to mail recipient. This opens the default outlook express and asks for a reduction in size of images. This reduces the size to a great extent and then you can save them back in your folder.

The second option is to open a typical editor(paint, photoeditor or adobe) and save the image as .png. When opening the saved image with IE, .png files won't be rendered as-in but size and resolution are both disturbed. However, if you keep the curser for a while on the image, an orange square displayed at the right end of the image appears. Clicking that restores the original size and resolution. I adopted this approach and mentioned the same in the context description section in my assumptions.html file.

Hope this helps

Thanks
Sankha Subhra das
Joseph,
Scalability is a required feature in the architecture design but Clustering, Load Balancing, Failover is NOT. Though it would be highly recommended to include these facets in the architecture, in practice these are "good-to-have" features. Also with these arise the necessity to ensure required respose time, failover management handling, logging and web session/transaction management if any. Sun's original intention might well be to allow clustering/failover specifying the two boxes but as an architect you should always think about fitting your architecture to the hardware and NOT hardware to the design.

Thanks
Sankha Subhra Das
Senthil,

Well, I did not need the controller component and hence did not use it for TA's. The business delegate + servicelocator components would be enuff to handle the right service. I however, had another a component for session handling which would basically maintain session data to be sent to-and-fro from TA's desktops. I handled session in the web tier instead of SFSB's.
If u really needed controller function, you can design it appropriately. Hope that helps

Thanks
Sankha Subhra Das
Senthil,
NO....DO NOT hide the web-tier in the sequence diagram for this reason. I depicted the web tier w.r.t the web users. In fact, for all my 4 sequence diagrams, I have modelled w.r.t the web customers only. Specific differences for the TA's was made a reference as comments only. For example, for Travel Agents you can write a seperate comment saying, TA's direct connect to the businessDelegate layer from the client tier.

Hope it helps.

Thanks
Sankha Subhra Das
I used EJB 2.0 for the assignment. I however, mentioned it in bold in the assumption section.

Thanks
Sankha Subhra Das
You can depict is as comment if its vital to support your architecture.


Thanks
Sankha Subhra Das