Your users want a more advanced user interface. You know that your system needs a service-oriented architecture. You're in luck! These two things actually go hand in hand. Not only can you get the best of both worlds but modern technologies and tools even make it fun to develop these systems. Find out how to build RESTful back-end systems with Grails. You can easily add a Flex front end, or you can try Ext GWT: a combination of Ext JS's rich widgets -- all on the Java™ platform, thanks to the Google Web Toolkit.