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JSP class loading settings

We can configure a JavaServer Pages (JSP) class to be loaded by either the JSP engine's class loader or by the web module's class loader.

By default, a JSP class is loaded by a unique instance of the JSP engine's class loader. The JSP engine's class loader enables reloading at runtime of a JSP class when the JSP source or one of its dependents is modified. This allows us to reload a single JSP class when necessary, without affecting any other loaded JSP classes.

JSP classes are loaded by the web module's class loader under either of the following scenarios.

  1. The JSP engine configuration parameter useFullPackageNames is set to true, and the JSP file is configured as a servlet in the web.xml file using the <servlet-class> scenario in the table later in this topic.

  2. The JSP engine configuration parameters useFullPackageNames and disableJspRuntimeCompilation are both set to true. In this case, we do not need to configure a JSP file does as a servlet in the web.xml file.


Configure JSP files as Servlets

We can configure a JSP file as a servlet in the web.xml file. There are two ways to do this. They are described in the table later in this section.

Before we configure a JSP file as a servlet, consider the following.

  1. Reloading capability - If runtime reloading of JavaServer Pages files is desired, requests for JavaServer Pages files must be handled by the JSP engine. The <servlet-class> scenario in the table later in this section disables runtime JSP file reloading, while the <jsp-file> scenario is compatible with reloading.

  2. Reducing the number of class loaders - If we do not require runtime reloading of modified JSP pages and we want to reduce the number of class loader instances, then we can use the <servlet-class> scenario in the table that follows. Similarly, scenario 2 in section 1 can be used without having to configure a JSP file as a servlet.

Scenario Example compatible with runtime reloading multiple class loaders used? useFullPackageNames
<jsp-file> <servlet>
<servlet-name>jspOne</servlet-name>
<jsp-file>jspOne.jsp</jsp-file>
</servlet> 		Yes Yes Can be true or false
<servlet-class> <servlet>
<servlet-name>jspTwo</servlet-name>
<servlet-class>_ibmjsp.jspTwo</servlet-class>
</servlet> 		No No Must be true

The JSP batch compiler tool helps we configure JavaServer Pages files as servlets. When useFullPackageNames is true, the JSP batch compiler generates <servlet> and <servlet-mapping> elements for each JSP file that it successfully translates and compiles. The elements are written to a web.xml fragment file named generated_web.xml located in the binaries WEB-INF directory of a web module processed by the JSP file batch compiler (this directory is located within the deployed application's ear file). We can copy and paste all or some of these elements into the web.xml file to configure JavaServer Pages files as servlets.

Take note of the location of the web.xml used by the application server. The application specific configuration is obtained from either the application binaries (the application's ear file) or from the configuration repository. If an application is deployed into WebSphere Application Server with the flag Use Binary Configuration set to true, then the WEB-INF/web.xml file is looked for in a web module's binaries directory, not in the configuration repository. Examples of these two locations follow:

If the JSP batch compiler is executed on a pre-deployed application then the web.xml file is in the web module's WEB-INF directory.

  • Configure JSP engine parameters
  • JavaServer Pages (JSP) runtime reloading settings