This method is called before the service is invoked.
Input
RequestContext - Contains session parameters, such as language cd, user id,
and so on.Input/Output
PageBody - The input page body to be added.Return value
PageBody or null - If a page body is returned, this is considered the result
of the service and the underlying service will not be executed. If null is returned,
the service will run normally.Throws
InterceptorError - Throw this exception when an error occurs.
InterceptorWarning - Throw this exception to signal an application
warning.