Hi Jeetendra
I think your question is very broad. There can be many ways you can create Forum application.
Before design, prepare/document all requirements of Forum application.
Requirements can be divided into various sub sections
a. Business Requirements - (how the forum should work from end user perspective for example - do we require to give change password option to User OR do we want system to generate a random new password when ever required etc ).
b. Technical Requirements - Here you decide hardware stack (how many servers required, any need of Load balancing etc ), software stack (which db to use,which programming language to be used, which web framework to be used, which ORM to be used ,which
Servlet Container OR
JEE containerto be used , which project management tool to be used etc)
c. Non functional requirements - performance criteria of Forum application, security features etc
Based on all requirements , you can create good design document.
By the way, you can use Open Source Java based Forum Application which can be customized toy your requirements.
Thanks
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