In this example we will leverage EclipseLink JAXB (MOXy)'s concepts of externalized metadata (represented as a MetadataSource), and extensible models. The MetadataSource will be used to define the metadata for the extensions. In EclipseLink 2.3 we have introduced the ability for a JAXBContext to be "refreshed". This means that without stopping the application we can supply metadata about new extensions.