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https://issues.apache.org/jira/browse/WW-3457?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12877332#action_12877332
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Jed Wesley-Smith commented on WW-3457:
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> Did you profile that ... ?
Yes, we saw this as one of the major causes of blocking in multi-threaded and a
significant hotspot in the single-threaded profiled runs.
> Solved, thanks!
Awesome!
> Significant performance improvement for freemarker TagModel
> -----------------------------------------------------------
>
> Key: WW-3457
> URL: https://issues.apache.org/jira/browse/WW-3457
> Project: Struts 2
> Issue Type: Improvement
> Affects Versions: 2.0.0
> Reporter: Jed Wesley-Smith
> Assignee: Lukasz Lenart
> Fix For: 2.2.0
>
>
> The class org.apache.struts2.views.freemarker.tags.TagModel creates a new
> freemarker.template.DefaultObjectWrapper for each call to
> unwrapParameters(Map). The problem is that that class is quite expensive to
> construct as the super-class does a quite bit of introspection to fill up its
> caches. Not only is this a lot of work, it tends to hit the Introspector
> class pretty hard, which internally does a lot of sychronising. In our soak
> performance tests this was a significant cause of blocking in our application.
> The DefaultObjectWrapper (or more properly the
> freemarker.ext.beans.BeansWrapper class as that is actually all the TagModel
> is using) is actually meant to be a cache that prevents exactly this kind of
> slowness, so constructing a new one every time is counter-productive.
> I don't have the latest source handy so I can't provide a patch, but the
> change is to simply replace the line:
> DefaultObjectWrapper objectWrapper = new DefaultObjectWrapper();
> with:
> BeansWrapper objectWrapper = BeansWrapper.getDefaultInstance();
> in the second line of TagModel.unwrapParameters(Map params)
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