ExternalGraphicFactory does not have a general way to reset caches

Description

The current implementations of ImageGraphicFactory and SVGGraphicFactory both use a cache internally and provide a resetCache() method. However, that method is not part of the interface – instead, GeoServer calls it directly in the WMSLifecycleHandler::onReset() method.
In order to support additional ExternalGraphicFactory implementations that also use a cache, there should be an additional interface (CachingExternalGraphicFactory?) that provides a general cache reset capability.
See discussion https://sourceforge.net/p/geoserver/mailman/message/35747439/

Environment

None

Status

Assignee

Unassigned

Reporter

David Vick

Triage

None

Fix versions

Affects versions

None

Priority

Medium
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