JavaServer Pages, Second Edition

Precompiling JSP Pages

To avoid hitting your site visitors with the delay caused by the conversion of a JSP page into a servlet on the first access, you can precompile all pages in the application. Another use of precompilation is if you don’t want anyone to change the pages in a JSP-based application after the application has been deployed. In this case, you can precompile all pages, define URL mappings for all JSP pages in the application deployment descriptor, and install just the Java class files for the compiled pages. We look at both these scenarios in this section.

One way of precompiling all pages in an application is to simply run through the application in a development environment and make sure you hit all pages. You can then copy the class files together with all the rest of the application to the production server when you deploy the application. Where the class files are stored varies between containers. Tomcat stores all JSP page implementation classes in its work directory by default, in a subdirectory per web application. As long as the modification date of the class files are more recent than the corresponding JSP pages, the production server uses the copied class files.

The JSP specification also defines a special request parameter that can give the JSP container a hint that the page should be compiled without letting the page process the request. An advantage of using this method is that you can automatically invoke each page, perhaps using a simple load testing ...