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JSP batch compilation

As an IBM enhancement to JSP support, IBM WebSphere Application Server provides a batch JSP compiler that allows JSP page compilation before application deployment. The batch compiler validates the syntax of JSP pages, translates the JSP pages into Java source files, and compiles the Java source files into Java servlet class files. The batch compiler also validates tag files and generates their Java implementation classes.

Batch compilation of JSP pages in a predeployed application simplifies the deployment process and improves the runtime performance of JSP page by eliminating first-request compilations. The batch compiler also operates on enterprise applications that have been deployed into WAS.

The JSP batch compiler works on web modules that support Servlet 2.2 and later. The batch compiler works on JSP pages written to the JSP 2.1 specification or previous specifications back to JSP 1.0. It recognizes a Servlet 2.5 or later deployment descriptor, web.xml, and can use any jsp-config elements that it may contain. In a Servlet 2.3 (JSP 1.2) or Servlet 2.2 (JSP 1.1) deployment descriptor the batch compiler recognizes and uses any taglib elements the descriptor may contain.

Batch compiling makes the first request for a JSP page much faster because the JSP page is already translated and compiled into a servlet. Batch compiling is also useful as a fast way to resynchronize all of the JSP pages for an application.

The batch compiler supports the generation of class files in both the WAS temp directory and a web module's WEB-INF/classes directory, depending on the type of batch compiler target. In addition, the batch compiler enables generation of class files into any directory on the filesystem, outside the target application. Generating class files into a web module's WEB-INF/classes directory enables the web module to be deployed as a self-contained WAR file, or a WAR inside an EAR.

Also, we can use shared libraries with the JSP batch complier. When we use the JSP batch compiler, either add the JAR to the WAR in the <WEB-INF>/lib directory , or add the JAR to the JVM class path to use shared libraries.

Subtopics

1. JSPBatchCompiler command
   
2. Batch compiler ant task
   
3. Batch compiler class path
   
4. Pre-touch tool for compiling and loading JSP files
   

Related concepts:

JSP class file generation
Packages and directories for generated .java and .class files
Global tag libraries (deprecated)
JSP

Reference:

Web container configuration for JSP static file access
Web applications: Resources for learning

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