XFireRuntimeException: Couldn't find a binding provider!

how can I call a webservice service by framework like xfire in workflow plugin module?
anyone did this?

when I new client
Client client = new Client(new URL(url));

got error:

org.codehaus.xfire.XFireRuntimeException: Couldn’t find a binding provider!. Nested exception is java.lang.ClassCastException: org.codehaus.xfire.aegis.AegisBindingProvider cannot be cast to org.codehaus.xfire.service.binding.BindingProvider

java.lang.ClassCastException: org.codehaus.xfire.aegis.AegisBindingProvider cannot be cast to org.codehaus.xfire.service.binding.BindingProvider