GDBMS is a middleware that allows accessing any kind data sources (data bases, files, ...) through the DataSource abstraction. It's also possible to make SQL queries to the data sources in order to filter, 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.
GDBMS begun on summer 2004 with the aim of accesing different kind of data with a common interface. We were working on the gvSIG project and soon realized that the easyest way to implement the alphanumeric data access was to integrate and improve GDBMS. The development was done in a chaotic way but always keeping in mind some XP principles: keep the design simple and refactor if it's not. This, with the accomplished objective of making the library highly customizable (drivers, functions, data types, ...) allowed the use of the library in other scenarios such as SWING frameoworks and spatial applications.