ragazzi sapete dirmi cos'è questo errore e come si risolve:

type Exception report

message

description The server encountered an internal error () that prevented it from fulfilling this request.

exception

java.lang.NullPointerException
GestioneXML.aggiungiClientiXML(GestioneXML.java:33 )
ServletRegistrati.doPost(ServletRegistrati.java:48 )
ServletRegistrati.doGet(ServletRegistrati.java:21)
javax.servlet.http.HttpServlet.service(HttpServlet .java:689)
javax.servlet.http.HttpServlet.service(HttpServlet .java:802)

note The full stack trace of the root cause is available in the Apache Tomcat/5.5.12 logs.