Class Not Found Issues

Preface

This page discusses the various ways you see Class Not Found errors or very similar errors. It is strongly advised you read the following topics:

• Classloader HOWTO pages: Tomcat 4.1, Tomcat 5.5, Tomcat 6.0.

• Don't use packageless classes and declare all imported classes!

• Another answer to a classloader issue

If you get a NoClassDefFoundError exception, the root cause might be the same as for a ClassNotFound exception.

Questions

1. Why is jsp:useBean is not working?

2. Why do I get java.lang.NoClassDefFoundError: javax/servlet/Filter?

3. Why do I get java.lang.NoClassDefFoundError: org/xml/sax/InputSource?

Answers

Why is  jsp:useBean  is not working?

Make sure:

• Your bean is packaged in a class.

• You have fully qualified your class name (eg: com.bar.package.MyClass ) OR

• You have imported your class into your jsp (eg:  <%@ page import="com.bar.package.MyClass"%> )

Why do I get  java.lang.NoClassDefFoundError: javax/servlet/Filter?

You probably have servlet.jar floating around somewhere it shouldn't be. This really messes up the classloaders since Tomcat's classloaders don't act quite as normal as one expects (see links above). servlet.jar should only be found only once in $CATALINA_HOME/common/lib.

Why do I get  java.lang.NoClassDefFoundError: org/xml/sax/InputSource ?

• You have conflicting XML api jar files in your classpath. Read the README or RELEASE-NOTES for more information.