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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:

• Wiki Markup
  Classloader HOWTO pages:

  Tomcat 7.0, Tomcat 6.0.
• Don't use packageless classes and declare all imported classes!

• \[http://tomcat.apache.org/tomcat-4.1-doc/class-loader-howto.html Tomcat 4.1\], \[http://tomcat.apache.org/tomcat-5.0-doc/class-loader-howto.html Tomcat 5.0\], \[http://tomcat.apache.org/tomcat-5.5-doc/class-loader-howto.html Tomcat 5.5\].

• Wiki Markup

  \[http://marc.theaimsgroup.com/?t=104317529200004&r=1&w=2 Don't\] \[http://marc.theaimsgroup.com/?t=104380440100003&r=1&w=2 use\] \[http://marc.theaimsgroup.com/?t=96947656900002&r=1&w=2 packageless\] \[http://marc.theaimsgroup.com/?t=104491020100002&r=1&w=2 classes\] \[http://marc.theaimsgroup.com/?t=104265576200003&r=1&w=2 and\] \[http://marc.theaimsgroup.com/?t=104249748300001&r=1&w=2 declare\] \[http://marc.theaimsgroup.com/?t=102996950100003&r=1&w=2 all\] \[http://marc.theaimsgroup.com/?t=102922189400001&r=1&w=2 imported classes\]!

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  \[http://marc.theaimsgroup.com/?l=tomcat-user&m=103843452413727&w=2 Another answer to a classloader issue\] \\

  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

Why is jsp:useBean is not working?

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Answers

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 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 eg:com.bar.package.MyClass ) OR
• You have imported your class into your jsp (e.g.: No Format <%@ page importeg: <%@ pageimport="com.bar.package.MyClass"%> )
  

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• Why do I get

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• java.lang.NoClassDefFoundError:

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• javax/servlet/Filter

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• ?*

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/common/lib. AnchorQ3Q3*

• Why do I get

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• java.lang.NoClassDefFoundError:

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• org/xml/sax/InputSource

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• ?*

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