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From "Craig R. McClanahan" <craig...@apache.org>
Subject Re: [dbcp] DBCP classloader in Tomcat 4.1.18
Date Sat, 15 Feb 2003 04:06:24 GMT


On Fri, 14 Feb 2003, Christopher M. Judd wrote:

> Date: Fri, 14 Feb 2003 22:56:15 -0500
> From: Christopher M. Judd <cjudd@columbus.rr.com>
> Reply-To: Jakarta Commons Developers List <commons-dev@jakarta.apache.org>
> To: Jakarta Commons <commons-dev@jakarta.apache.org>
> Subject: [dbcp] DBCP classloader in Tomcat 4.1.18
>
> I am building a web application using Tomcat 4.1.18, Struts 1.1 b3 and
> MSSQL. I have used Struts 1.0 in the past and configured the datasources
> in struts-config.xml file. This is my first attempt at using Struts 1.1
> b3 and datasource configurations in the struts-config.xml file have been
> deprecated. I tried to configure the datasource using JNDI several times
> with no luck. I repeatedly got ClassNotFoundExceptions on the MSSQL
> driver class. I tried placing the MSSQL jars in the WEB-INF/lib of my
> web app, in the server/lib and in the shared/lib. Finally I tried
> creating a JSP and doing a Class.forName(). The JSP could find the class
> so I realized after many hours of trial and error it must be a
> Classloader issue. I finally found the common/lib directory and that
> worked. After thinking about it I realize the issue and that the
> common/lib jars must be in a different Classloader. However, I am
> wondering if there is an issue with the way commons-dbcp locates and
> loads classes. Requiring database jars to reside in the common/lib and
> not in the web applications WEB-INF/lib reduces flexibility.
>

What happens if the data source (connection pool) you are configuring is
shared between webapps?  That's going to cause a pretty significant
problem.

If you are using JNDI-based resources, you are saying (in effect) that it
is the container's responsibility to provide you with that object,
completely configured and ready for use by a webapp.  Therefore, it
doesn't make sense to include any of the classes in your webapp itself --
instead, you need to make them part of the container (Tomcat in this case)
configuration.

Craig


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