[jira] [Commented] (HADOOP-9424) The "hadoop jar" invocation should include the passed jar on the classpath as a whole

["Sangjin Lee (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/HADOOP-9424?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15414532#comment-15414532 ] 

Sangjin Lee commented on HADOOP-9424:
-------------------------------------

Coming over from HADOOP-13410, I would rather take the opposite approach. What's included in HADOOP_CLASSPATH should be considered more like "user classes". I would rather put the content of HADOOP_CLASSPATH in the user classloader that loads the jar and remove it from the CLASSPATH. That way, the jar in the argument and the content of the HADOOP_CLASSPATH would be visible to each other. Note that the isolated classloading (HADOOP_CLIENT_CLASSLOADER) already takes that approach.

> 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
>              Labels: BB2015-05-TBR
>         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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