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From Dale Newfield <D...@Newfield.org>
Subject Re: [struts] Slow performance with Struts2
Date Thu, 03 Jul 2008 00:34:46 GMT
yorlick kilroy wrote:
> I'm sorry but I only just read about javassist now, as I had no idea what it
> is nor does. How do I include it? do I just drop it in my lib folder like I
> do with other Struts plugins? How do I use it? and what exactly does it do?

Yes, just drop the .jar into your WEB-INF/lib directory. 
http://www.csg.is.titech.ac.jp/~chiba/javassist/

I believe it's used by ognl, if present.  "Javassist is a Java library 
providing means to manipulate the Java bytecode of an application. In 
this sense Javassist provides the support for structural reflection, 
i.e. the ability to change the implementation of a class at runtime." 
Basically if I understand it correctly, ognl2.7 can do some amount of 
"expression compilation" in such a way that less work is needed when 
those same (sub?) expressions are next evaluated.

I believe most of the benefits won't be realized until we jump through a 
number of hoops in our use of ognl that we've yet to implement in 
xwork2/struts2, but if this (possibly premature) "upgrade" actively 
slows down ognl evaluation, I'd like to know.  (Since I swapped in these 
more recent ognl version in the project I'm currently developing, I'd 
really like to know if that was a step backwards.)

-Dale

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