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 ? 
