Can somebody suggest what would be the best way to implement such a converter tool?Difficult to say - I don't think there is a straightforward way to automate this process. The route I would explore, if I had to, is to let JavaFX 1.3 handle the parsing of JavaFX 1.3 code by loading the FXD documents into JavaFX 1.3, then recurse over the nodes of the added documents to write out an FXML file using an XML lib or Groovy's XML processing capabilities - that way you don't need to write an FXD parser or adapt a JSON parser. You wouldn't end up with an exact translation, but perhaps it would end up close enough that you could hand tweak or XSLT the XML output to workable FXML. But whether the effort to build such a tool would outweigh the effort of hand translating to FXML I'm not sure. You don't really want a 1:1 translation of the files as FXML and JavaFX 1.3 are differ beyond syntactic considerations (e.g. constructs such as layout panes, controls, public object properties and binding mechanisms differ in both their structure and semantics), so whatever you do, some manual post processing is going to be required.