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https://issues.apache.org/jira/browse/HADOOP-12803?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15174000#comment-15174000
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Jason Lowe commented on HADOOP-12803:
-------------------------------------
Thanks for the patch, Gera! Unfortunately this breaks backwards
compatibility. For example, http://wiki.apache.org/hadoop/WordCount references
this sample command-line:
{quote}
bin/hadoop jar hadoop-*-examples.jar wordcount [-m <#maps>] [-r <#reducers>]
<in-dir> <out-dir>
{quote}
With the proposed change it results in this error:
{noformat}
Exception in thread "main" java.lang.ClassNotFoundException: wordcount
at java.net.URLClassLoader$1.run(URLClassLoader.java:366)
at java.net.URLClassLoader$1.run(URLClassLoader.java:355)
at java.security.AccessController.doPrivileged(Native Method)
at java.net.URLClassLoader.findClass(URLClassLoader.java:354)
at java.lang.ClassLoader.loadClass(ClassLoader.java:424)
at java.lang.ClassLoader.loadClass(ClassLoader.java:357)
at java.lang.Class.forName0(Native Method)
at java.lang.Class.forName(Class.java:270)
at org.apache.hadoop.util.RunJar.run(RunJar.java:231)
at org.apache.hadoop.util.RunJar.main(RunJar.java:139)
{noformat}
I'm not sure how we're going to differentiate a main class from an arbitrary
first argument to pass on. Previously it used the presence of a main class in
the manifest to know whether the first argument is a main class or the first
argument to the program being launched. Not necessarily how I would have done
it, but that's how it works and users have built things around those semantics.
> RunJar should allow overriding the manifest Main-Class via a cli parameter.
> ---------------------------------------------------------------------------
>
> Key: HADOOP-12803
> URL: https://issues.apache.org/jira/browse/HADOOP-12803
> Project: Hadoop Common
> Issue Type: Bug
> Components: util
> Affects Versions: 2.6.4
> Reporter: Gera Shegalov
> Assignee: Gera Shegalov
> Attachments: HADOOP-12803.001.patch
>
>
> Currently there is no way to override the main class in the manifest even
> though main class can be passed as a parameter.
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