You can add custom functionality to the error handling mechanism without changing the default error pages.
To replace the default error handing mechanism with a custom one, you have to develop your own HTML file, or a JSP, or servlet within an application. After deploying this application you have to set the related properties using the Config Tool:
Global_app_config/error_page/context_root defines the name of the application which is responsible for the error handling mechanism.
Global_app_config/error_page/location specifies the name of the servlet that takes care of the error processing.
To change the values of these properties, proceed as follows:
In the Config Tool, choose View and select the Expert Mode checkbox.
Expand the nodes
and select the servlet_jsp node.Select the property you want to specify. Enter the new value in the Custom Value field and choose Set Custom Value.
Choose (Apply changes).