"Note that the leading tool for Web Services testing is SoapUI. While this product provides some powerful support for Soap based mock services, its support for REST based mock services is almost non-existent (basically, just setting up a separate test case for each endpoint and sending a file). The UltraESB environment was a much cleaner solution for putting together the mock services, particularly with the IntelliJ IDE for writing the code. I could load the payload, read it into a string, manipulate it, the write it back out to the payload. The learning curve was very minimal. Great job!"
The UltraESB recently started supporting RESTful JSON Data Services more information on the JSON support is available from http://jsonesb.org