I have the following code :

soapHttpTransport.setAuthToken(authToken);

Element requestModifyAppt = Element.XMLElement.mFactory.createElement(MailCons tants.MODIFY_APPOINTMENT_REQUEST);
requestModifyAppt.addAttribute(MailConstants.A_ID, "398-397");

Element msgElement = Element.XMLElement.mFactory.createElement(MailCons tants.E_MSG);
msgElement.addAttribute(MailConstants.A_REPLY_TYPE , "w");

requestModifyAppt.addAttribute(MailConstants.A_TOK EN, authToken);

requestModifyAppt.addAttribute(MailConstants.A_CAL _START_TIME, "20091019T000000");

requestModifyAppt.addAttribute(MailConstants.A_CAL _START_TIME, "20091019T040000");

requestModifyAppt.addAttribute(MailConstants.A_CAL _LOCATION, "location ddd");

requestModifyAppt.addAttribute(MailConstants.E_NAM E, "name test");

requestModifyAppt.addAttribute(MailConstants.A_FOL DER, ZFolder.ID_CALENDAR);


requestModifyAppt.addElement(msgElement);

Element responseModifyAppt = null;
try
{
responseModifyAppt = soapHttpTransport.invoke(requestModifyAppt);
}
catch (SoapFaultException e)
{
e.printStackTrace();
}
catch (IOException e)
{
e.printStackTrace();
}


But I have the folloing exception :

com.zimbra.common.soap.SoapFaultException: system failure: java.lang.NullPointerException
ExceptionId:btpool0-13:1255963940487:f27fc284109a7913
Code:service.FAILURE
at com.zimbra.common.soap.Soap12Protocol.soapFault(So ap12Protocol.java:88)
at com.zimbra.common.soap.SoapTransport.extractBodyEl ement(SoapTransport.java:263)
at com.zimbra.common.soap.SoapTransport.parseSoapResp onse(SoapTransport.java:224)
at com.zimbra.common.soap.SoapHttpTransport.invoke(So apHttpTransport.java:262)
at com.zimbra.common.soap.SoapHttpTransport.invoke(So apHttpTransport.java:217)
at com.zimbra.common.soap.SoapTransport.invoke(SoapTr ansport.java:315)
at com.zimbra.common.soap.SoapTransport.invoke(SoapTr ansport.java:279)

Can you help me