ExternalContext abstracts context, request and response information so that compile-time dependencies on the
Servlet API or Portlet API can be removed.
The Filesystem resource manager is able to load resources from the filesystem with a direct
mapping, or, if the property is specified, within a sandbox.
When this processor is created based on a declaration in an XML document, the LocationData
provides information about the location of this declaration.
Subclasses can use this utility method when implementing the getKey
and getValidity methods to make sure that they don't read the whole
config (if we don't already have it) just to return a key/validity.
This method is used by processor implementations to store state information tied to the
current execution of the current processor, across processor initialization as well as reads
of all the processor's outputs.