I have not yet programmed a JSP program but I think a big
advantage of using JSP is that your code is not 'sandboxed'
and has no browser restrictions ie. opening streams to
arbitary sites. Also, the browser dosnt have to have a java
plug-in installed as most (?all GPL distros?) linux distros
dont because java isnt open source.

I worked both swing  and JSP.could u tell me what are
the things could not be done on JSP than swing?.I will come to my problem.I
have an swing application which is developed using JApplet and JTree and
JFrame.This will displays data's from database as tree structure and using
frames.

I would need some insight into what the current applet does and what you
expect to do with JSP before I could make any useful comparison. I don't
really know how to compare these two very different technologies. I suspect
from the way that your question was worded that you have a bit of a
misunderstanding about what JSP gives you. The basic differences are:

- Applets run on the client side and are used primarily to do things that can
not be done using just HTML.

- JSP runs on the server and generates HTML.

Given that, if you already have an applet, I am assuming that it was written
because you wanted to do something that could not be done (or at least done
as well) with HTML. If that is the case, JSP is not going to solve your
problem.