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 7.0, 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

Answers

*Why is

 jsp:useBean

is not working?*

Make sure:

Your bean is packaged in a class.
You have fully qualified your class name (e.g.:
```
 com.bar.package.MyClass 
```
) OR
You have imported your class into your jsp (e.g.:
```
 <%@ page import="com.bar.package.MyClass"%> 
```
)

*Why do I get

 java.lang.NoClassDefFoundError: javax/servlet/Filter

?*

You probably have servlet-api.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-api.jar should only be found only once in $CATALINA_HOME/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.

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FAQ Class Not Found

Class Not Found Issues

Preface

Questions

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