The BPEL integration tooling allows you to configure a transformer between WSDL and the Java interface as a JAXB transformer. This results in an error.
This happens because JAXB transformations are only valid for data objects that contain JAXB annotations or include an ObjectFactory in a configured context path. A string does not qualify, so using JAXB in this context is invalid. More constraints need to be added to the tooling to ensure that only valid data is input.