The source you provided seems to doesnt much the exception, Im not able to see any use of InputStream. You have to take a look to at com.sap.util.monitor.grmg.GrmgRequest.<init>(GrmgRequest.java:75). The service you have wrote seems to provocate this somehow, so it has to be presented in the stack trace, if I got you properly. Hang in there with NWDS and debug if you are not sure whats going wrong. The trace is a bit too short, you are not able to more in the logs regarding this issue? No "caused by" or any attendant exceptions?
cheers