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https://issues.apache.org/jira/browse/SOLR-972?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Kay Kay updated SOLR-972:
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    Attachment: SOLR-972.patch

> EventListener are not created per request ( full / delta-imports) but rather 
> instantiated once per lifetime of the application - maintaining state + 
> efficient 
> ---------------------------------------------------------------------------------------------------------------------------------------------------------------
>
>                 Key: SOLR-972
>                 URL: https://issues.apache.org/jira/browse/SOLR-972
>             Project: Solr
>          Issue Type: Improvement
>          Components: contrib - DataImportHandler
>         Environment: Java 6, Tomcat 6
>            Reporter: Kay Kay
>             Fix For: 1.4
>
>         Attachments: SOLR-972.patch
>
>   Original Estimate: 2h
>  Remaining Estimate: 2h
>
> The EventListener plugin for notification of start / end import events 
> (SOLR-938) creates an instance of EventListener before every notification. 
> This has 2 drawbacks. 
> * No state is stored between successive invocations of events as it is a new 
> object 
> * When writing plugins for delta imports - it is very inefficient to do a 
> class loader lookup by reflection / instantiate an instance and call a method 
> on the same. 
> Attached patch has one EventListener through the lifetime of the DIH plugin . 
> Also EventListener is changed to an interface rather than an abstract class 
> for better decoupling (especially painful when the start/end eventlistener 
> has an independent hierarchy by itself ). 
> By default, a no-op listener is registered to avoid boiler plate code to 
> check if there is a start / end listener specified.  Efficient JRE impls 
> should be able to optimize the no-op for minimum overhead compared to 
> checking the reference for null and branching out. 
> Specifying an onImportStart / onImportEnd overrides the default handler 
> though. 

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