[jira] Commented: (MAPREDUCE-1686) ClassNotFoundException for custom format classes provided in libjars

["Amareshwari Sriramadasu (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/MAPREDUCE-1686?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12888221#action_12888221 ] 

Amareshwari Sriramadasu commented on MAPREDUCE-1686:
----------------------------------------------------

Paul, Can you create the patch with suggested change and a unit test, and upload here? 

> ClassNotFoundException for custom format classes provided in libjars
> --------------------------------------------------------------------
>
>                 Key: MAPREDUCE-1686
>                 URL: https://issues.apache.org/jira/browse/MAPREDUCE-1686
>             Project: Hadoop Map/Reduce
>          Issue Type: Bug
>          Components: contrib/streaming
>    Affects Versions: 0.20.2
>            Reporter: Paul Burkhardt
>            Priority: Minor
>
> The StreamUtil::goodClassOrNull method assumes user-provided classes have package names and if not, they are part of the Hadoop Streaming package. For example, using custom InputFormat or OutputFormat classes without package names will fail with a ClassNotFound exception which is not indicative given the classes are provided in the libjars option. Admittedly, most Java packages should have a package name so this should rarely come up.
> Possible resolution options:
> 1) modify the error message to include the actual classname that was attempted in the goodClassOrNull method
> 2) call the Configuration::getClassByName method first and if class not found check for default package name and try the call again
> {code}
>     public static Class goodClassOrNull(Configuration conf, String className, String defaultPackage) {
>         Class clazz = null;
>         try {
>             clazz = conf.getClassByName(className);
>         } catch (ClassNotFoundException cnf) {
>         }
>         if (clazz == null) {
>             if (className.indexOf('.') == -1 && defaultPackage != null) {
>                 className = defaultPackage + "." + className;
>                 try {
>                     clazz = conf.getClassByName(className);
>                 } catch (ClassNotFoundException cnf) {
>                 }
>             }
>         }
>         return clazz;
>     }
> {code}

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