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Date: Fri, 20 Jul 2012 22:46:47 -0700
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Subject: Re: controlling ClassLoader when programmatically invoking Ant
From: Mitch Gitman <mgitman@gmail.com>
To: Ant Developers List <dev@ant.apache.org>
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P.S. I'm going to give URLClassLoader a shot with the JARs in Ant lib:
http://docs.oracle.com/javase/6/docs/api/java/net/URLClassLoader.html

Almost sounds a little too easy...

On Fri, Jul 20, 2012 at 10:37 PM, Mitch Gitman <mgitman@gmail.com> wrote:

> Technically, this message is better suited for the ant-user list, but I'm
> thinking I'm more apt to get an answer on this list. (I'm also thinking
> this is the better place for me to cash in some chits for my having
> submitted patches for three Ivy issues I mentioned recently on this list.
> Subject: "extends and buildlist on 2.3.0-rc1....")
>
> Here's my problem. I'm trying to do a JUnit test of some Ivy functionality
> (actually, relating to the aforementioned Ivy bugs) by programmatically
> creating and executing an Ant Project object. Everything runs just fine.
> I'm able to execute targets and even tie in a BuildListener and a
> BuildLogger to tap into output and error and check if the build failed.
>
> The problem is, everything works a little too well. Take a look at the
> following example build.xml:
> <project xmlns:ivy="antlib:org.apache.ivy.ant" name="resolve-test"
> default="build">
>
>     <target name="build">
>     <ivy:settings file="ivysettings.xml" />
>     <ivy:resolve ... />
>     </target>
> </project>
>
> I've abbreviated the ivy:resolve call, but take it from me that everything
> works, including running the test directly from within an IDE. It
> shouldn't. Nowhere am I specifying the classpath containing the JAR for Ivy
> itself. Nowhere am I even doing the taskdef for Ivy.
>
> And in fact, if I run this build.xml straight from the command line, it
> fails like you would expect:
> Problem: failed to create task or type antlib:org.apache.ivy.ant:settings
> ...
>
> I can only think that the key method I want to take advantage of is this
> in Project:
>     public void setCoreLoader(ClassLoader coreLoader) {
>         this.coreLoader = coreLoader;
>     }
>
> What's interesting is that the command-line entry point for Ant in
> org.apache.tools.ant.Main ends up passing null to setCoreLoader, in which
> case "the parent classloader should be used," according to the method's
> Javadoc. At this point, I go take a look at the scripts that launch Ant and
> my eyes get blurry. But I believe what I want to do is manually construct a
> ClassLoader as if I were running "java -cp ..." with the contents of Ant's
> lib directory. (I'm showing my ignorance of ClassLoaders here, I realize.)
> Perhaps someone can point me to an elegant way to accomplish that.
>
> If someone's going to say, "Hey, check what antunit does," I'd appreciate
> if you could pinpoint what it's doing.
>
> P.S. Perhaps somebody has a rational explanation too for why the taskdef
> of Ivy is creeping in.
>

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