[HADOOP-3665] WritableComparator newKey() fails for NullWritable

• Type: Bug
• Status: Closed
• Priority: Minor
• Resolution: Fixed
• Affects Version/s: 0.16.0
• Fix Version/s: 0.18.0
• Component/s: io

Environment

n/a

• Hadoop Flags: Incompatible change, Reviewed
• Assignee: Christopher Douglas
• Reporter: Lukas Vlcek
• Created: 29/Jun/08 21:41
• Updated: 22/Aug/08 19:50
• Resolved: 03/Jul/08 23:47

Description

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

Issue Links

• is related to: HADOOP-2922 sequencefiles without keys