The parser registry is used to parse the XML and build a configuration holder object that contains all existing configurations, some of which are used as base for entity/collection/query caching.

> what other classes are consumed/utilized by external clients

^ No idea what you mean.

I don't see why you need `globalConfiguration.aggregateClassLoader()` here. Shouldn't ConfigurationHolder's classloader really be `globalConfiguration.aggregateClassLoader()` ? That should avoid the need for injection?