An approach to expose ABAP REST services
1: develop a class in ABAP with public methods
2: implement interface ZIF_SWAG_HANDLER, and register the public methods(example method zif_swag_handler~meta)
3: the methods are now accessible via rest(example)
4: the Swagger UI can be accessed via swagger.html in the base dir of the REST services
Install via abapGit
Requires native JSON support see http://scn.sap.com/community/abap/blog/2013/01/07/abap-and-json or SAP note 1648418