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From "Owen O'Malley (JIRA)" <j...@apache.org>
Subject [jira] Commented: (MAPREDUCE-954) The new interface's Context objects should be interfaces
Date Thu, 10 Sep 2009 22:35:58 GMT

    [ https://issues.apache.org/jira/browse/MAPREDUCE-954?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12753867#action_12753867
] 

Owen O'Malley commented on MAPREDUCE-954:
-----------------------------------------

Only application frameworks like ChainMapper will implement Contexts. Applications should
only use Contexts.

The MapperImpl is private to map/reduce and will only consist of a method to create a ContextImpl.
No other method on it will ever be called. ContextImpl will have the method bodies to implement
the context and will be given the user in the places where a Mapper.Context is required.

Since the Context objects are public, we will need to allow bodies on methods to support backwards
compatibility of frameworks as we add methods to them, so they will start as pure abstract
classes and slowly gain default bodies for added methods.

> The new interface's Context objects should be interfaces
> --------------------------------------------------------
>
>                 Key: MAPREDUCE-954
>                 URL: https://issues.apache.org/jira/browse/MAPREDUCE-954
>             Project: Hadoop Map/Reduce
>          Issue Type: Improvement
>          Components: client
>            Reporter: Owen O'Malley
>            Assignee: Arun C Murthy
>             Fix For: 0.21.0
>
>         Attachments: MAPREDUCE-954.patch
>
>
> When I was doing HADOOP-1230, I was persuaded to make the Context objects as classes.
I think that was a serious mistake. It caused a lot of information leakage into the public
classes.

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