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Servlet sequence diagrams

 
Andy Verkeyn
Greenhorn
Posts: 6
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Hi,


I'm currently preparing for the SCWCD exam with the HFSJ book.
In the process of trying to understand what really goes on when web applications and servlets get initialized and servlets handle requests (and also how it happens), I have drawn a few UML sequence diagrams.
I would like to ask other ranchers to validate my diagrams. If you find a sequence that is wrong according to the servlet specification, or another assumption that doesn't make sense to you, please let me know! Also, all other comments and (constructive) critics are welcome.

Be warned that I provide more details than strictly required for the exam. I know this is one of my (many) bad habits: if I need to understand something, I always want full details on conceptual level. It is simply stronger than myself. :-)

The diagrams can be found at my website,
http://www.verkeyn.net/computer/download/servlets_start.pdf
http://www.verkeyn.net/computer/download/servlets_request.pdf
http://www.verkeyn.net/computer/download/servlets_attrib.pdf

Remarks:
- I have only finished reading the chapter on JSPs, so filters are not (yet) included on the diagrams.
- The diagrams are meant to increase my understanding on the servlet subject, so UML is used as a means not a goal. E.g. I have shown two objects s:GenericServlet and s:HttpServlet for one and the same object because I wanted to make clear in which interface the involved operations are defined. It is not correct UML but it helps me, so I prefer it like that.
- I wanted to make the diagrams completely self-contained. E.g. if a ServletConfig object is initialized with servlet config init parameters, I include an operation that reads those from the deployment descriptor. E.g. if the container runs a servlet in a thread, I have included the thread and the start of the servlet.
- I have shown object destruction after an implicit call of the finalize() method. To make a clear distinction between explicit and implicit calls, the implicit finalize calls are shown with dashed lines (again not true UML).
- I have named my server object apache and my container object tomcat, but the goal is to understand the general servlet specification, I am not focused on the internals of Tomcat.

Please let me know if you find errors! Thanks in advance!

By the way: you may use the diagrams for your own purposes, but I do not take responsibility for potential errors, usage is at your own risk!


Kind regards,
Andy
 
Imran Vohra
Ranch Hand
Posts: 77
Chrome Eclipse IDE Java
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Given links are not working on my machine.
Can you please confirm those links?

Imran
 
Andy Verkeyn
Greenhorn
Posts: 6
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They do work at my computer (and it's not the same computer where I have the files locally), so it should be allright I think...

Maybe you can try to go to the HTML page:
http://www.verkeyn.net/computer
(and click Java)

Or even

http://www.verkeyn.net
(and click Computer Science - Java)

Hope this helps.

Regards,
Andy
 
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