hi all I have extends a sip servlet
 
package org.example.servlet.sip;
 
import java.io.IOException;
import java.io.PrintWriter;
 
import javax.servlet.ServletConfig;
import javax.servlet.ServletException;
import javax.servlet.sip.SipServlet;
import javax.servlet.sip.SipServletRequest;
import javax.servlet.sip.SipServletResponse;
 
public class SimpleServlet extends SipServlet {
 
/**
*
*/
 
public SimpleServlet() {
// TODO Auto-generated constructor stub
System.out.println("hi \n amer22222222 \n");
}
private static final long serialVersionUID = -468618845319795003L;
 
@Override
protected void doRegister(SipServletRequest req) throws ServletException,
IOException {
System.out.print("hi \n hi \n hi \n hi \n hi \n");
}
 
 
public void doInvite(SipServletRequest request) {
 
System.out.println("*** Received INVITE ***");
 
try {
request.createResponse(SipServletResponse.SC_RINGING).send();
//request.createResponse(SipServletResponse.SC_OK).send();
} catch (IOException e) {
e.printStackTrace();
}
 
}
 
public void doCancel(SipServletRequest request) {
 
System.out.println("*** Received CANCEL ***");
 
try {
request.createResponse(SipServletResponse.SC_REQUEST_TERMINATED).send();
} catch (IOException e) {
e.printStackTrace();
}
 
}
 
 
@Override
public void init(ServletConfig servletConfig) throws ServletException {
System.out.println("****** the simple sip servlet has been started ********* \n ya rab");
 
}
}
and after I run the server I have the error

HTTP Status 500 -
please I need help any Ideas ?

the error stack 
 
#   Sep 27, 2010 2:06:10 AM org.apache.catalina.core.StandardWrapperValve invoke  
# SEVERE: Servlet.service() for servlet SimpleServlet threw exception  
# java.lang.ClassCastException: org.apache.catalina.connector.RequestFacade cannot be cast to javax.servlet.sip.SipServletRequest  
#     at javax.servlet.sip.SipServlet.service(SipServlet.java:325)  
#     at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:290)  
#     at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)  
#     at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:233)  
#     at org.mobicents.servlet.sip.startup.SipStandardContextValve.invoke(SipStandardContextValve.java:248)  
#     at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:128)  
#     at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:102)  
#     at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109)  
#     at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:293)  
#     at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:849)  
#     at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:583)  
#     at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:454)  
#     at java.lang.Thread.run(Thread.java:619)