null pointer exception

am just a beginner to Web Services. I was following a tutorial about web services and i am using WSDP. I created two java classes one an interface and the other which implemented that. I complied these two classes. Now I am trying to create a war file of my package. But I am getting a null pointer exception when I try to run wsdeploy command.

error msg: java.lang.NullPointerException at com.sun.xml.rpc.tools.wsdeploy.DeployTool.defineServletsAndListeners(DeployTool.java:447)

[493 byte] By [nishchal.bhata] at [2007-10-2 10:54:44]