JSP class loading

 

JSP class loading

You 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 you 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. 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 below.

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

Configuring JSP files as Servlets

You 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 below. Before you 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 below disables runtime JSP file reloading, while the <jsp-file> scenario is compatible with reloading.

  2. Reducing the number of class loaders - If you do not require runtime reloading of modified JSP pages and you want to reduce the number of class loader instances, then you can use the <servlet-class> scenario in the table below. Similarly, scenario 2 in section 1 above 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 you 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 which is 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). You 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 that is used by the application server. In WebSphere Application Server 6.0, 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. Below are examples of these two locations.

  1. An example of a configuration repository directory is 
    {WAS_ROOT}/profiles/profilename/config/cells/
cellname/applications/enterpriseappname/deployments/deployedname /webmodulename

  2. An example of an application binaries directory is: 
    {WAS_ROOT}/profiles/
profilename/installedApps/nodename/EnterpriseAppName/WebModuleName /

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.

Related tasks
Configuring JSP engine parameters

Related reference
Configuring JSP runtime reloading