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From Mitch Gitman <mgit...@gmail.com>
Subject Ant + Spring = classpath purgatory
Date Sat, 29 Jan 2011 07:33:56 GMT
I have a Spring-based application that I'm exposing through an Ant task,
among other interfaces.

The moment where I run into trouble is when the application tries to use
Spring's ClassLoader-based code to load a Spring application context:
        ApplicationContext applicationContext = new
ClassPathXmlApplicationContext(
                "/com/foo/ApplicationContext.xml");

I see an error that the resource com/foo/ApplicationContext.xml cannot be
found on the classpath. The XML file, together with the application code,
happen to be in the same JAR as the task itself.

Now, I came across this very, very old post on the ant-dev list that gave me
the makings of a solution:
http://www.mail-archive.com/dev@ant.apache.org/msg07704.html

So at the start of my task, I would do this:
        AntClassLoader taskloader = (AntClassLoader)
this.getClass().getClassLoader();
        taskloader.setThreadContextLoader();

And at the close of my task, I would do this:
        taskloader.resetThreadContextLoader();

This works actually.*

I'm leery though of having to resort to this fix. Does anyone know of a
"better" way to get Spring to use the right ClassLoader or just in general
to fool task-invoked application code that might play fast and loose with
classloaders? I haven't delved into the Spring source myself. What's odd is
that this problem doesn't arise in other classloading containers in which a
Spring-based application might be running. For example, a web container
would be loading a web application with a child classloader, and yet that
works fine.

Thanks.

* Rather, this almost works. Almost in that Spring tries to configure its
logging through log4j, but it can't find the class
org.apache.log4j.Category. I've verified that the log4j JAR is in my
classpath. The quick fix is to stick the log4j JAR in the Ant lib directory.
Obviously, that is not a sustainable solution. I'm still trying to get to
the bottom of this and might have to write a follow-up message.

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