Introduction
The HAPI FHIR Plain Server module can be used to create a FHIR server endpoint against an arbitrary data source, which could be a database of your own design, an existing clinical system, a set of files, or anything else you come up with.
HAPI also provides a persistence module which can be used to provide a complete RESTful server implementation, backed by a database of your choosing. This module uses the JPA 2.0 API to store data in a database without depending on any specific database technology.