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Permalink to this page: https://cwiki.apache.org/confluence/x/tSklBg

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 9.0, Tomcat 8.5, Tomcat 7.0, (historic: 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.

...

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

Anchor
Q1 Q1

...

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.:

  No Format

  com.bar.package.MyClass

  ) OR

• You have imported your class into your jsp (e.g.:

  No Format

  <%@

  page

  import="com.bar.package.MyClass"%>

   )

Anchor
Q2 Q2

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Why do I get

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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.

Anchor
Q3 Q3

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Why do I get

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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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