Java Servlet & JSP Cookbook

Problem

You want to use the "precompilation protocol" that is part of the JSP specification to precompile one or more JSP files.

Solution

Send a request to the JSP container that includes a jsp_precompile parameter.

Discussion

The JSP 1.2 and 2.0 specifications require compliant JSP containers to support the use of the jsp_precompile request parameter. This parameter suggests that the container precompile the requested JSP. Here is how it works in Tomcat:

1. Request the JSP that you want precompiled with the jsp_precompile parameter added to the URL, as in http://localhost:8080/home/url_rewrite.jsp?jsp_precompile=true .

   The JSP container is not supposed to execute the JSP page; it just precompiles it. The result of the request, if you were making it in a web browser, is a blank page.

2. If the JSP file in JSP page syntax has not yet been compiled, or if the JSP file has been changed and has a later modification date than any existing page implementation class, Tomcat creates a new Java source and class file for the JSP in the <Tomcat-install-directory>/work directory. If the JSP file is named url_rewrite.jsp , Tomcat calls the Java source and class files url_rewrite_jsp.java and url_rewrite_jsp.class .

   Supplying the request parameter jsp_precompile (without the "=true" part) is the same as requesting jsp_precompile =true in the URL.

This protocol is best used with an automated tool that can make HTTP requests , such as the Jakarta Commons HttpClient component. Using such a tool allows you to automate the precompilation of dozens of JSPs by sending several HTTP requests from a single Java program.

See Also

Recipe 5.1 on using Tomcat's JspC utility; Recipe 5.2 on precompiling with WebLogic Server; Recipe 5.4 on mapping the compiled JSPs in web.xml ; Chapter 7 on sending HTTP requests from a servlet or a JSP; the Jakarta Commons HttpClient homepage at http://jakarta.apache.org/commons/httpclient/; The JSP precompilation section of JavaServer Pages by Hans Bergsten (O'Reilly); Chapter JSP.11.4 of the JSP 2.0 specification.