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From "Radim Kolar (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HADOOP-8619) WritableComparator must implement no-arg constructor
Date Mon, 30 Jul 2012 09:32:34 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-8619?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13424776#comment-13424776
] 

Radim Kolar commented on HADOOP-8619:
-------------------------------------

There is difference between think and know. To make object serialization work, all referenced
objects must be deserializable, otherwise there is no way to reconstruct object tree back.
You can not deserialize object if you can no create it. Plain and simple.

Lets take another approach: Hadoop is using findbugs, isnt it? It means that you guys have
some trust and confidence in findbugs authors. Then trust them if they are telling you that
deserialization do not works if you cant call constructor.
                
> WritableComparator must implement no-arg constructor
> ----------------------------------------------------
>
>                 Key: HADOOP-8619
>                 URL: https://issues.apache.org/jira/browse/HADOOP-8619
>             Project: Hadoop Common
>          Issue Type: Improvement
>          Components: io
>    Affects Versions: 3.0.0
>            Reporter: Radim Kolar
>             Fix For: 0.23.0, 2.0.0-alpha, 3.0.0
>
>         Attachments: writable-comparator.txt
>
>
> Because of reasons listed here: http://findbugs.sourceforge.net/bugDescriptions.html#SE_COMPARATOR_SHOULD_BE_SERIALIZABLE
> comparators should be serializable. To make deserialization work, it is required that
all superclasses have no-arg constructor. http://findbugs.sourceforge.net/bugDescriptions.html#SE_NO_SUITABLE_CONSTRUCTOR
> Simply add no=arg constructor to  WritableComparator.

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