how to get SOAP Message while Request in WebService.. ?

i am working on Web Logic WebService. I have created Web service and deployed
into server. 

But now is there any ways to get the SOAP Message while request because i want
to add some headers to the my SOAP Message before it sent to the backend. 

SOAPMessageContext smc=null;
SOAPMessage soapMsg = smc.getMessage();
System.out.println("SOAP MESSAGE :"+soapMsg);

But I am getting  NullPointerException.

any Help ??...

ThankQ.