I've used Selenium to do lots of UI testing from the browser. If you have a web service behind the Java jsp page i.e. in a servlet, you can test it from Selenium.

Can Selenium be used to test a B2B web service i.e. a web service called from a backend that has no browser UI component?

I have used SOAPUI to do this kind of testing in the past but our test department is trying to standardise on Selenium.