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From rmenon <>
Subject Re: Digester 1.8 classloader issue when using tomcat
Date Sat, 03 Jan 2009 20:44:37 GMT

Can you please elaborate? Are you suggesting that I should just package all
three jar files in WEB-INF/lib? 

Rahul Akolkar wrote:
> On Sat, Jan 3, 2009 at 2:14 PM, rmenon <> wrote:
>> Hi
>> I have three jar files: common, webapp-common, my-webapp.jar.
>> common- can be used by non web apps
>> webapp-common - common stuff shared by web apps.
>> my-webapp.jar - a particular web app.
>>  I am using digester to build my classes for the app my-webapp.jar. In
>> the
>> digester rules, I have classes that are in all three jar files. Now,
>> ideally
>> speaking, I should be able to put the webapp-cmmon and common jar files
>> in
>> the shared/lib and the my-webapp.jar in WEB-INF/lib. However, that
>> results
>> in the digester failing with "NoClassDefFoundException". The problem goes
>> away if we put all three jars in the WEB-INF/lib since the digester class
>> loader can see those classes. However, the common jar is already in the
>> shared/lib being used by other apps. I added some new "common" stuff for
>> the
>> my-webapp.jar and hence running into this issue.
>> My latest thinking is to separate out the portion of the classes being
>> used
>> by the my-webapp.jar from the common jar file into its own jar. Then I
>> can
>> bundle the webapp-common ahd my-webapp.jar in to the WEBINF/lib and
>> retain
>> the common jar in the shared/lib. Is there a better approach? What is the
>> best practice in this scenario. Does someone have an idea of overhead in
>> terms of performance etc if we "duplicate" jar files in each app instead
>> of
>> sharing them in common/lib? What I do not like about this issue is that I
>> think this issue would not be there if I was creating objects without
>> using
>> digester - so a way to use the approach (where I can access the common
>> classes from digester) would be really ideal in my opinion.
>> I did search the google and also this forum - I note that someone
>> suggested
>> to always bundle each jar files within the web app itself separately.
>> What
>> is the rationale for that?
> <snip/>
> Portability, potential trouble with statics etc. Also, digester itself
> (and beanutils in particular) should never be shared.
> -Rahul
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