Significant performance improvement for freemarker TagModel
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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
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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