ResourceDefinition instances are only used during subsystem registration. Unfortunately, the Undertow subsystem references each ResourceDefinition instance in a static reference, which prevents their garbage collection once subsystem registration is complete.
AFAICT, these static references are only used by the PersistentResourceXMLParser implementations to obtain the PathElement of a given ResourceDefinition - even though static references to all PathElement instances already exist.
Eliminating these static references will reduce the metaspace overhead of this subsystem by allowing all ResourceDefinition instances to be garbage collected after the initial subsystem registration.