I tried a modified version of JAXB2 example in xfire-1.2.5 where I added a oneway method defined which has the signature @WebMethod @Oneway public void AddWeather(@WebParam(name="AddWeather") AddWeather weather, @WebParam(name="ModuleParam", header=true) ModuleParam param); Certainly I added the corresponding elements to the XSD. When I tried to call this service method, the result was a NullPointerException: java.lang.NullPointerException at org.codehaus.xfire.service.binding.ServiceInvocationHandler.fillInHolders(ServiceInvocationHandler.java:290) at org.codehaus.xfire.service.binding.ServiceInvocationHandler.fillInHolders(ServiceInvocationHandler.java:251) at org.codehaus.xfire.service.binding.ServiceInvocationHandler.invoke(ServiceInvocationHandler.java:73) at org.codehaus.xfire.handler.HandlerPipeline.invoke(HandlerPipeline.java:131) at org.codehaus.xfire.transport.DefaultEndpoint.onReceive(DefaultEndpoint.java:64) at org.codehaus.xfire.transport.AbstractChannel.receive(AbstractChannel.java:38) at org.codehaus.xfire.transport.http.XFireServletController.invoke(XFireServletController.java:304) at org.codehaus.xfire.transport.http.XFireServletController.doService(XFireServletController.java:129) at org.codehaus.xfire.transport.http.XFireServlet.doPost(XFireServlet.java:116) at javax.servlet.http.HttpServlet.service(HttpServlet.java:717) at javax.servlet.http.HttpServlet.service(HttpServlet.java:810) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:252) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:173) at org.jboss.web.tomcat.filters.ReplyHeaderFilter.doFilter(ReplyHeaderFilter.java:96) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:202) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:173) at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:213) at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:178) at org.jboss.web.tomcat.security.SecurityAssociationValve.invoke(SecurityAssociationValve.java:175) at org.jboss.web.tomcat.security.JaccContextValve.invoke(JaccContextValve.java:74) at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:126) at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:105) at org.jboss.web.tomcat.tc5.jca.CachedConnectionValve.invoke(CachedConnectionValve.java:156) at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:107) at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:148) at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:869) at org.apache.coyote.http11.Http11BaseProtocol$Http11ConnectionHandler.processConnection(Http11BaseProtocol.java:664) at org.apache.tomcat.util.net.PoolTcpEndpoint.processSocket(PoolTcpEndpoint.java:527) at org.apache.tomcat.util.net.MasterSlaveWorkerThread.run(MasterSlaveWorkerThread.java:112) at java.lang.Thread.run(Thread.java:595) When I added a check for outMsg and outHeaderMsg != null before calling fillInHeaders with signature private void fillInHolders(MessagePartContainer msg, Object[] newParams) everything worked but I'm not sure that it's the correct solution.