why no calss def error in tomcat?

hello guys, i am writting some code that uses oreilly servlet upload package and namely the multipart request class..

the code compiles fine but when called by the container during execution, the following message is outputted:

type Exception report

message

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

exception

javax.servlet.ServletException: Servlet execution threw an exception

root cause

java.lang.NoClassDefFoundError: com/oreilly/servlet/MultipartRequest

NewPicServlet.doPost(NewPicServlet.java:62)

javax.servlet.http.HttpServlet.service(HttpServlet.java:709)

javax.servlet.http.HttpServlet.service(HttpServlet.java:802)

note The full stack trace of the root cause is available in the Apache Tomcat/5.5.17 logs.

why?

[867 byte] By [ketsona] at [2007-10-3 2:33:39]
# 1
its ok.. i have solved it...forgot to copy the jar file in tomcat lib directory.....
ketsona at 2007-7-14 19:32:38 > top of Java-index,Enterprise & Remote Computing,Web Tier APIs...