why WSPasswordCallback.getPassword is null when I try my soap request

i
            
         I have made axis 2 web service with rampart security 
but I constantly was receiving null point exception at this line 
if((pwcb.getIdentifier().equals("bob")) && pwcb.getPassword().equals("bobPW")) )  
so when I wrote this code 
if ( pwcb.getPassword()==null)
{  throw new Exception ("passsssssssss is null:"+pwcb.getPassword());  
I saw at last that the problem is that pwcb.getPassword is null and I can't explain why
Thank you in advance
 
  
this is my soaprequest  
"<?xml version=\"1.0\" encoding=\"utf-8\"?>" + "<soapenv:Envelope " +  "xmlns:soapenv=\"http://schemas.xmlsoap.org/soap/envelope/\" " + "xmlns:nilo=\"http://nilo\">"+ "<soapenv:Header>"+ '<wsse:Security xmlns:wsse=\"http://docs.oasis-open.org/wss/2004/01/oasis-200401-wss-wssecurity-secext-1.0.xsd\" soapenv:mustUnderstand="1">'+ '<wsse:UsernameToken xmlns:wsu="http://docs.oasisopen.org/wss/2004/01/oasis-200401-wss-wssecurity-utility-1.0.xsd" wsu:Id="123">'+ '<wsse:Username>bob</wsse:Username>'+ '<wsse:Password Type="http://docs.oasis-open.org/wss/2004/01/oasis-200401-wss-username-token-profile-1.0#PasswordText">bobPW</wsse:Password>'+ '</wsse:UsernameToken>'+ '</wsse:Security>'+ "</soapenv:Header>"+ "<soapenv:Body>" + "<nilo:getdataForChecking>" + '<nilo:data>'+tranXml+'</nilo:data>' + ' </nilo:getdataForChecking>'+ '</soapenv:Body>' + '</soapenv:Envelope>'; 
 
 
My PWCBHandler.java class 
public void handle(Callback[] callbacks)   throws IOException,  UnsupportedCallbackException  { 
for (int i = 0; i < callbacks.length; i++) { //When the server side need to authenticate the user WSPasswordCallback pwcb = (WSPasswordCallback)callbacks[i]; if ( pwcb.getPassword()==null) { try { throw new Exception ("passsssssssss null:"+pwcb.getPassword()); } catch (Exception e) { // TODO Auto-generated catch block e.printStackTrace(); } } else  { try { throw new Exception ("pass nooot null:"+pwcb.getPassword()); } catch (Exception e) { // TODO Auto-generated catch block e.printStackTrace(); } } if(pwcb.getIdentifier().equals("bob") && pwcb.getPassword().equals("bobPW")) { return;  }