java - Servlet: Cannot instantiate javaURLContextFactory only if load-on-startup -

in tomcat 7 (jdk 1.7) have servlet in load on startup returns error:

javax.naming.noinitialcontextexception: cannot instantiate class: org.apache.naming.java.javaurlcontextfactory [root exception java.lang.classnotfoundexception: org.apache.naming.java.javaurlcontextfactory] 

but if call same servlet browser runs.

the error occurs on servlet init() method invoked on start only. seems missing 1 or more jar files classpath

tomcat 6 , 7 support servlet 2.5 standard. standard includes better way web-server-bootstrap actions, through servletcontextlistener interface.

tomcat 7 supports servlet 3.0 standard, can annotate class avoid web.xml configuratiuon

import javax.servlet.*; import javax.servlet.annotation.*;  @weblistener public class bootstrapthewebserver implements servletcontextlistener {      @override     public void contextinitialized(servletcontextevent event)   {         // invoked on web server start          // event.getservletcontext() servlet context     }      @override     public void contextdestroyed(servletcontextevent event) {       // invoked on web server shutdown      } }