[ https://issues.apache.org/jira/browse/WW-4433?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14547881#comment-14547881 ] 

Marzieh Beiraghdar commented on WW-4433:
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Thank you for the update. :-) It fixes the problem. Still i like to know how to register a customize unknown handler.
 Please let me know what i am doing wrong. 

> ConventionUnknownHandler change breaks exception handling in interceptors.
> --------------------------------------------------------------------------
>
>                 Key: WW-4433
>                 URL: https://issues.apache.org/jira/browse/WW-4433
>             Project: Struts 2
>          Issue Type: Bug
>          Components: Core Interceptors, Documentation, Plugin - Convention
>    Affects Versions: 2.3.20
>            Reporter: Joseph Wolschon
>            Assignee: Lukasz Lenart
>            Priority: Minor
>             Fix For: 2.3.24
>
>
> Struts 2.3.20 appears to have caused a regression that prevents exceptions thrown from convention-plugin actions from reaching ExceptionMappingInterceptor. This breaks exception handling when using the convention-plugin.
> To Reproduce: 
> * Generate a project struts2-archetype-convention archetype using 2.3.20
> * Throw exception in the action. With 2.3.20, a blank page is shown.
> * Change to 2.3.16.3 and you will get the standard struts2 error page.
> The breaking change appears to have been made in WW-4331. This causes error interceptor code to break (showing a blank page when exceptions are thrown) as DefaultActionInvocation does not catch an exception from the default UnknownHandler implementation execution, which would previously re-throw the original exception back up for the interceptors to catch. 
> Workaround:
> We've created our own UnknownHandler implementation that just throws a new NoSuchMethodException, allowing DefaultActionInvocation to re-throw the original exception so that our error interceptor can again catch it.



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