Disable JSP run-time compilation

The JSP engine translates a requested JSP file, compiles the .java file, and loads the compiled servlet into the run-time environment. In previous versions of WAS, if a .class file did not exist, the JSP engine always translated and compiled the JSP file. You had to turn off the reload capability of Web applications to prevent additional translations and recompiles of the file.

In WAS V5.0.1, you can change the default behavior of the JSP engine by indicating that a JSP file should never be translated or compiled at run time, even when a .class file does not exist.

If run-time compilation is disabled, precompile the JSP files, which provides the following advantages:

• Reduces compilation related disk operations.
• Minimizes disk storage requirements necessary for handling temporary .java and .class files generated during a run-time compilation.
• Forces the verification that a JSP file compiled successfully before deploying and installing the application in WAS.

You can disable JSP file run-time compilation for all Web applications or for a specific Web application:

• Disable compilation for all Web applications
  To disable the translation and compilation of JSP files for all Web applications, set the Web container Custom property disableJspRuntimeCompilation to true.

  To set this property, perform the following steps:

  1. Start the administrative console.
  2. In the topology tree, expand Servers.
  3. Expand Application Servers and click Application Servers.
  4. Click your application server.
  5. Click Web Container.
  6. Click Custom Properties, and select disableJspRuntimeCompilation

  Valid values for this setting are true or false. If this property is set to true, then translation and compilation of the JSP files is disabled at run time for all Web applications.

• Disable compilation for a specific Web application
  To disable the translation and compilation of JSP files for a specific Web application, set the JSP engine initialization parameter disableJspRuntimeCompilation to true. When this setting is enabled, it determines the run-time behavior of the JSP engine and overrides the Web container custom property setting.

  Set this parameter through the JavaServer Pages attribute assembly settings panel in the Application Assembly Tool (AAT).

  To set this parameter, perform the following steps:

  1. Start the Application Assembly Tool.
  2. Open the Web module you want to modify.
  3. Expand Assembly Property Extensions under the Web module.
  4. Right-click JSP Attributes and select New.
  5. Set the value of Name to disableJspRuntimeCompilation.
  6. Set the value of Value to true.
  7. Click File --> Save.
  8. (Optional) If you are working with a compressed Web module, install the modified module.
  9. If the application server is running, use the administrative console to stop the application server, then start it.

  Valid values for this setting are true or false. If this parameter is set to true, translation and compilation of the JSP files is disabled at run time, and the JSP engine only loads precompiled files for the specific Web application.

Implications of disabling JSP run-time compilation

If the Web container custom property or the JSP attribute assembly parameter is not set, the first request for a JSP file results in the translation and compilation of the JSP file when the .class file does not exist. Subsequent requests for the file also result in compilations and translations, but only if the following conditions are met:

• Compilations and translations are required.
• Reloading is enabled for the Web module.
• Reload interval is exceeded.

If you disable run-time compilation and a request arrives for a JSP file that does not have a matching .class file, the JSP engine returns HTTP error 501 (Not implemented) to the browser. If the JSP file does not exist, the JSP engine returns HTTP error 404 (File not found) to the browser. In both cases, an exception is written to the System Out (SYSOUT) and First Failure Data Capture (FFDC) logs. If a JSP file has a matching .class file but that file is out of date, the JSP engine still loads the .class file into memory.

Perform the following steps to determine whether the disableJspRuntimeCompilation option is enabled in WAS:

1. Enable the Diagnostic Trace Service and set the trace specification to com.ibm.ws.webcontainer.jsp.servlet.*=all=enabled.
2. Request a JSP file.
3. Locate the string, disableJspRuntimeCompilation:true, in the trace.log file.
4. Ensure the jspUri: entry matches the requested JSP file.

If both the disableJspRuntimeCompilation:true string and the matching jspUri: entry appear in the trace, the disableJspRuntimeCompilation setting is enabled for the Web application.