[jira] Issue Comment Edited: (HADOOP-3665) WritableComparator newKey() fails for NullWritable

["Arun C Murthy (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/HADOOP-3665?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12609753#action_12609753 ] 

acmurthy edited comment on HADOOP-3665 at 7/1/08 5:25 PM:
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I'm ok with this patch, though making WritableComparator a Configurable might be a stretch... given that we don't have and Configurable Writables. But I'm happy to bow down to the wisdom of the crowd.

      was (Author: acmurthy):
    I'm ok with this patch, though making WritableComparator a Configurable might be a stretch...
  
> WritableComparator newKey() fails for NullWritable
> --------------------------------------------------
>
>                 Key: HADOOP-3665
>                 URL: https://issues.apache.org/jira/browse/HADOOP-3665
>             Project: Hadoop Core
>          Issue Type: Bug
>          Components: io
>    Affects Versions: 0.16.0
>         Environment: n/a
>            Reporter: Lukas Vlcek
>            Priority: Minor
>             Fix For: 0.19.0
>
>         Attachments: 3665-0.patch, 3665-1.patch, HADOOP-3665.path
>
>
> It is not possible to use NullWritable as a key in order to suppress key value in output.
> Syndrome exception:
> Caused by: java.lang.IllegalAccessException: Class org.apache.hadoop.io.WritableComparator can not access a member of class org.apache.hadoop.io.NullWritable with modifiers "private"
> The problem is that NullWritable is a singleton and does not provide public non-parametric constructor. The following code in WritableComparator causes the exception: return (WritableComparable)keyClass.newInstance();
> Proposed simple solution is to use ReflectionUtils instead (it requires modification as well).
> This issue is probably related to HADOOP-2922

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