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From "Owen O'Malley (JIRA)" <j...@apache.org>
Subject [jira] Issue Comment Edited: (HADOOP-1231) Add generics to Mapper and Reducer interfaces
Date Thu, 05 Jul 2007 21:44:04 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-1231?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_12510490
] 

Owen O'Malley edited comment on HADOOP-1231 at 7/5/07 2:42 PM:
---------------------------------------------------------------

The signatures for JobConf.setMapperClass and setReducerClass should not have parameters.
I'd suggest:

{code}
public void setMapperClass(Class<? extends Mapper> mapper); 
public void setReducerClass(Class<? extends Reducer> reducer);
{code}

In terms of {{LongSumReducer}} and other generic mappers and reducers, I'd be tempted to allow
the user to write either the anonymous class that you suggested or use the current solution
of:

{code}
  grepJob.setReducerClass(LongSumReducer.class);
  grepJob.setOutputValueClass(Text.class);
{code}


 was:
The signatures for JobConf.setMapperClass and setReducerClass should not have parameters.
I'd suggest:

{{{code}}}
public void setMapperClass(Class<? extends Mapper> mapper); 
public void setReducerClass(Class<? extends Reducer> reducer);
{{{code}}}

In terms of {{LongSumReducer}} and other generic mappers and reducers, I'd be tempted to allow
the user to write either the anonymous class that you suggested or use the current solution
of:

{{{code}}}
  grepJob.setReducerClass(LongSumReducer.class);
  grepJob.setOutputValueClass(Text.class);
{{{code}}}

> Add generics to Mapper and Reducer interfaces
> ---------------------------------------------
>
>                 Key: HADOOP-1231
>                 URL: https://issues.apache.org/jira/browse/HADOOP-1231
>             Project: Hadoop
>          Issue Type: Improvement
>          Components: mapred
>            Reporter: Owen O'Malley
>            Assignee: Tom White
>         Attachments: HADOOP-1231.patch
>
>
> By making the input and output types of the Mapper and Reducers generic, we can get the
information from the classes and not require the user to set them in the configuration.

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