Does anybody knows how to read MUMPS database(GTM) using JAVA application or any open source tool?
I have to read MUMPS database of WorldVistA application using our java application/any mediator application.
Is there any tool for mapping mumps database to RDBMS?
You are asking the wrong question. For VistA, MUMPS is the raw data store. However, VistA is an enterprise scale application that has its own embedded database management system called Fileman, and the units of organization (analogous to tables in an RDBMS, but not exactly the same, are called files). So, your question is really how to access Fileman files from Java. This in turn translates to the question of how to call from Java the functions by which Fileman makes its files available to application code.
GT.M has a Java plugin (go to https://sourceforge.net/projects/fis-gtm/files/Plugins/GTMJI/ and get the latest version) that allows Java code to call MUMPS functions, and vice versa.
Also, you really want a tool to map Fileman files to SQL tables and expose the SQL tables. There are two tools: the Medsphere FM SQL Projection (http://www.medsphere.com/open-vista/technology/fm-sql-projection) and KB_SQL (http://knowledgebasedsys.com).
Incidentally, if you want to ask VistA questions, the VistA techies hang out on the Hardhats mailing list, which you can access at http://groups.google.com/group/hardhats (and likely other places as well). Note that accessing VistA data from Java is the beginning of a journey, not a destination. It is a journey along a path that many have taken. My advice is to learn from, and build on, their experiences, rather than starting your journey from scratch.