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From "Colin Patrick McCabe (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HADOOP-9424) The "hadoop jar" invocation should include the passed jar on the classpath as a whole
Date Thu, 21 Mar 2013 17:29:15 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-9424?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13609152#comment-13609152
] 

Colin Patrick McCabe commented on HADOOP-9424:
----------------------------------------------

This looks reasonable.  I can't think of any reason we wouldn't want to put the passed jar
on the classpath before invoking RunJar.
                
> The "hadoop jar" invocation should include the passed jar on the classpath as a whole
> -------------------------------------------------------------------------------------
>
>                 Key: HADOOP-9424
>                 URL: https://issues.apache.org/jira/browse/HADOOP-9424
>             Project: Hadoop Common
>          Issue Type: Bug
>          Components: util
>    Affects Versions: 2.0.3-alpha
>            Reporter: Harsh J
>            Assignee: Harsh J
>            Priority: Minor
>         Attachments: HADOOP-9424.patch
>
>
> When you have a case such as this:
> {{X.jar -> Classes = Main, Foo}}
> {{Y.jar -> Classes = Bar}}
> With implementation details such as:
> * Main references Bar and invokes a public, static method on it.
> * Bar does a class lookup to find Foo (Class.forName("Foo")).
> Then when you do a {{HADOOP_CLASSPATH=Y.jar hadoop jar X.jar Main}}, the Bar's method
fails with a ClassNotFound exception cause of the way RunJar runs.
> RunJar extracts the passed jar and includes its contents on the ClassLoader of its current
thread but the {{Class.forName(…)}} call from another class does not check that class loader
and hence cannot find the class as its not on any classpath it is aware of.
> The script of "hadoop jar" should ideally include the passed jar argument to the CLASSPATH
before RunJar is invoked, for this above case to pass.

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