Evaluate dynamically constructed JSP at runtime

I have a requirement where in the JSP page itself is created by the user and stored in the database. When viewing results we need to render this JSP to the client, evaluating all tags inside this JSP.

I am aware that it is doable as OpenCMS and Blogger both implement this functionality. But, I just can't find the right way.

Any pointers on how to do this?

[Added] Note: I cannot write a temporary file on disk for the purp开发者_StackOverflow中文版ose :(

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As ChssPly76 pointed out in the comment this issue was recently discussed. You can just store it as file in the webcontent and forward the request to it. See the link for an code example which I posted.