Factors for Servlets and JSP

Dear Ranchers,
A design level question....
When do i go for servlets? When do i go for JSP?
Since both are going to be finally servlets.....
While designing an Web App when do i say this will be a JSP and
this will be a servlet?
Is there a rule of thumb to say this functionality will be better implemented by Servlet or JSP?
Where would a Servlet fit better than JSP(Examples)?
Thanks
YRK

you have to use the mvc design pattern to facilitate proper separation of servlet and jsp.
a servlet acts as the c(controller),which verifies from data,updates the model with the form data,and selects the next view as the response.
a jsp pages acts as the view ,which renders the html response,and and provides html form to permit user interaction.

And don't forget - JSP are designed to serve character streams only - if you need to serve image or other binary resource data, it will have to be with a servlet. See numerous discussions on the JSP forum about images.
JSP should be regarded as a convenience only - for applications that have a preponderence of pre-formatted HTML. If your HTML involves a lot of computed content, a servlet is probably best.
Bill