[jira] [Commented] (YARN-4457) Cleanup unchecked types for EventHandler

["Karthik Kambatla (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/YARN-4457?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15287757#comment-15287757 ] 

Karthik Kambatla commented on YARN-4457:
----------------------------------------

Thanks for taking the time to clean these up. 

One rather high-level question: since all meaningful events have a type, shouldn't the dispatcher itself be generic? Are there dispatchers that serve events with closest common ancestor being only Event and no other subtype? If we do that, would we be able to typify these EventHandlers better than just <Event>? 


> Cleanup unchecked types for EventHandler
> ----------------------------------------
>
>                 Key: YARN-4457
>                 URL: https://issues.apache.org/jira/browse/YARN-4457
>             Project: Hadoop YARN
>          Issue Type: Improvement
>    Affects Versions: 2.7.1
>            Reporter: Daniel Templeton
>            Assignee: Daniel Templeton
>         Attachments: YARN-4457.001.patch, YARN-4457.002.patch, YARN-4457.003.patch, YARN-4457.004.patch, YARN-4457.005.patch
>
>
> The EventHandler class is often used in an untyped context resulting in a bunch of warnings about unchecked usage.  The culprit is the {{Dispatcher.getHandler()}} method.  Fixing the typing on the method to return {{EventHandler<Event>}} instead of {{EventHandler}} clears up the errors and doesn't not introduce any incompatible changes.  In the case that some code does:
> {code}
> EventHandler h = dispatcher.getHandler();
> {code}
> it will still work and will issue a compiler warning about raw types.  There are, however, no instances of this issue in the current source base.



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