GDBMS is a middleware that claims to allow accessing any kind data sources (data bases, files, ...) through the DataSource abstraction. It's shall also be possible to make SQL queries to the data sources in order to filter and to order the data they contains.
The GDBMS gvSIG plugins project gives GDBMS some useful features. First, there are some adapters from gvSIG drivers to GDBMS drivers: shapefiles, dgn, dwg, dxf, postgis, wfs, and so on (for a list of already built drivers check the orbisCAD capabilities). Second, it provides a utility class to get JTS geometries from the GDBMS spatial DataSources.