NullpointerException Please Help

Hello, I have the following function: function recuperaDati(myurl,suffix,endPoint,operation){ var request = new WSRequest(); var options = new Array(); var payload = null; var response = null; request.openWSDL(myurl+"/"+suffix+"/"+endPoint+"?wsdl",false); request.send(operation,payload); response = request.resposeXML; return response; } And it works, but when called it returns a null pointer exception. I tested the dataservice called with the tryIT function form the web interface and it works fine. It seems that if you use null for the payload you get the exception, but if you use a void string the server claims that you haven't passed a parameter. Here is the stack trace: org.wso2.mashup.MashupFault: java.lang.NullPointerException at org.wso2.mashup.hostobjects.wsrequest.WSRequestHostImpl.jsFunction_send(WSRequestHostImpl.java:799) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source) at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source) at java.lang.reflect.Method.invoke(Unknown Source) at org.mozilla.javascript.MemberBox.invoke(MemberBox.java:155) at org.mozilla.javascript.FunctionObject.call(FunctionObject.java:411) at org.mozilla.javascript.optimizer.OptRuntime.call2(OptRuntime.java:76) at org.mozilla.javascript.gen.c255._c1(c102217-CAMMash:25) at org.mozilla.javascript.gen.c255.call(c102217-CAMMash) at org.mozilla.javascript.optimizer.OptRuntime.callName(OptRuntime.java:97) at org.mozilla.javascript.gen.c255._c2(c102217-CAMMash:34) at org.mozilla.javascript.gen.c255.call(c102217-CAMMash) at org.mozilla.javascript.ContextFactory.doTopCall(ContextFactory.java:393) at org.mozilla.javascript.ScriptRuntime.doTopCall(ScriptRuntime.java:2834) at org.mozilla.javascript.gen.c255.call(c102217-CAMMash) at org.wso2.javascript.rhino.JavaScriptEngine.call(JavaScriptEngine.java:180) at org.wso2.javascript.rhino.JavaScriptEngine.call(JavaScriptEngine.java:210) at org.wso2.javascript.rhino.JavaScriptReceiver.invokeBusinessLogic(JavaScriptReceiver.java:195) at org.apache.axis2.receivers.AbstractInOutMessageReceiver.invokeBusinessLogic(AbstractInOutMessageReceiver.java:40) at org.apache.axis2.receivers.AbstractMessageReceiver.receive(AbstractMessageReceiver.java:100) at org.apache.axis2.engine.AxisEngine.receive(AxisEngine.java:176) at org.apache.axis2.transport.http.HTTPTransportUtils.processHTTPPostRequest(HTTPTransportUtils.java:275) at org.apache.axis2.transport.http.AxisServlet.doPost(AxisServlet.java:131) at org.wso2.mashup.transport.MashupServlet.doPost(MashupServlet.java:69) at javax.servlet.http.HttpServlet.service(HttpServlet.java:709) at javax.servlet.http.HttpServlet.service(HttpServlet.java:802) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:269) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:188) at org.wso2.mashup.transport.ServiceUIFilter.doFilter(ServiceUIFilter.java:207) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:215) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:188) at org.wso2.adminui.AdminUIServletFilter.doFilter(AdminUIServletFilter.java:135) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:215) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:188) at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:210) at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:174) at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:127) at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:117) at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:108) at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:151) at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:870) at org.apache.coyote.http11.Http11BaseProtocol$Http11ConnectionHandler.processConnection(Http11BaseProtocol.java:665) at org.apache.tomcat.util.net.PoolTcpEndpoint.processSocket(PoolTcpEndpoint.java:528) at org.apache.tomcat.util.net.LeaderFollowerWorkerThread.runIt(LeaderFollowerWorkerThread.java:81) at org.apache.tomcat.util.threads.ThreadPool$ControlRunnable.run(ThreadPool.java:685) at java.lang.Thread.run(Unknown Source) Caused by: org.apache.axis2.AxisFault: java.lang.NullPointerException at org.apache.axis2.util.Utils.getInboundFaultFromMessageContext(Utils.java:512) at org.apache.axis2.description.OutInAxisOperationClient.handleResponse(OutInAxisOperation.java:370) at org.apache.axis2.description.OutInAxisOperationClient.send(OutInAxisOperation.java:416) at org.apache.axis2.description.OutInAxisOperationClient.executeImpl(OutInAxisOperation.java:228) at org.apache.axis2.client.OperationClient.execute(OperationClient.java:163) at org.apache.axis2.client.ServiceClient.sendReceive(ServiceClient.java:548) at org.wso2.mashup.hostobjects.wsrequest.WSRequestHostImpl.jsFunction_send(WSRequestHostImpl.java:772) ... 46 more