What are the disadvantages of JSP?
2. Debugging JSP programs is still a major challenge.You have to remember that a jsp page will be first converted to a .java file and then compiled. Thus, any errors will be pointing to line numbers in the converted .java file and not the .jsp page.For example an error in the first line of .jsp page may be shown on the 20th line of the .java file. Tracing back can be somewhat tricky. (However, with the servlet engine Resin, the errors refer to the line within the .jsp page.) You can debug JSP pages using IDEs like VA Java and JDeveloper; but I think debugging JSP using an high-powered IDE would go against one of the basic tenets of JSP - simplicity.
3. Database connectivity is not as easy as it should be. Most of the servlet engine vendors do not support connection pooling natively, as of this day. Consequently, one has to write a lot of custom code to do the job.
5. There are numerous syntax related issues with JSP programming. Jason Hunter, author of 'Java servlet programming' has written an interesting article comparing JSP with other scripting alternatives. You can read the article at http://www.servlets.com/soapbox/problems-jsp.html.