Requirement for _default_ eviction region

[brian.stansberry]

Follow-on to our discussion on http://jira.jboss.org/jira/browse/JBCACHE-1288

Looking at RegionManager for other reasons and noticed this bit in getRegion(Fqn, Region.Type, boolean):

 // test if the default region has been defined. If not, and if eviction regions
 // are in use, throw an exception since it is required.
 if ((nextBestThing == null || nextBestThing.getFqn().isRoot() && !regionsRegistry.containsKey(Fqn.ROOT))
 && type == EVICTION)
 {
 if (log.isTraceEnabled())
 log.trace("Next best region is " + nextBestThing + ". RegionsRegistry contains a default? " + regionsRegistry.containsKey(Fqn.ROOT) + " Region type requested = " + type);
 throw new RuntimeException("No default eviction region defined!");
 }

Looks like we *are* enforcing a requirement for a _default_ region.

[brian.stansberry]

Looking at the usage of this method, only code that passes in Region.Type.EVICTION is EvictionInterceptor.canIgnoreEvent(). And that can handle a null return just fine. So, seems we could safely replace the above with:

 // test if the default region has been defined. If not, and if the request
 // is for an eviction region, return null
 if ((nextBestThing != null && nextBestThing.getFqn().isRoot() && !regionsRegistry.containsKey(Fqn.ROOT))
 && type == EVICTION)
 {
 log.trace("No default eviction region; returning null");
 nextBestThing = null;
 }

Haven't looked carefully to see if the method contract implies it won't return null.

[brian.stansberry]

And, change the if test order so "type == EVICTION" comes first. :-)

[manik]

Hmm, good point. And this plays much better into what we expect with default behaviour.