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From "Lukas Vlcek (JIRA)" <j...@apache.org>
Subject [jira] Created: (HADOOP-3665) WritableComparator newKey() fails for NullWritable
Date Sun, 29 Jun 2008 21:41:45 GMT
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: 0.17.0, 0.16.4, 0.16.3, 0.16.2, 0.16.1, 0.16.0
         Environment: n/a
            Reporter: Lukas Vlcek
            Priority: Minor
             Fix For: 0.19.0

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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