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copied!<p>The really annoying thing about akka is that you need to update the thread local context classloader for the generic setting, and a lot of tools (like sbt) do not, because they do not know what thread you're running on or which classloader you will need.</p> <p>Here's <a href="https://github.com/typesafehub/activator/blob/master/project/LocalTemplateRepo.scala#L45-L50" rel="nofollow">an example from the activator</a> build:</p> <pre><code>val cl = ??? // Some mechanism of getting Akka's classpath with your classes too val old = Thread.currentThread.getContextClassLoader Thread.currentThread.setContextClassLoader(cl) try doSomethingWithAkka() finally Thread.currentThread.setContextClassLoader(old) </code></pre> <hr/> <p>Edit (by OP) so that this is more visible than in the comments:</p> <p>Akka (since 2.0) chooses the class loader it uses in ActorSystem (when it's not passed as an argument) by picking the first available (and non-null) among:</p> <ol> <li><code>Thread.currentThread.getContextClassLoader</code></li> <li><code>getClassLoader</code> on the class of a non-Akka stack frame up the call stack</li> <li><code>ActorSystem.getClass.getClassLoader</code></li> </ol> <p>So that's why the above solution of mutating the context class loader works. </p> <p>As to the class loader to use in practice, I got the expected behaviour with <code>val cl = getClass.getClassLoader</code> (from my build definition class) since that class loader contains all the build definition, plugins and dependencies. Also it effectively makes step 1 above behave like step 2.</p> <p>In the end though, I've settled with just creating the ActorSystem by calling <code>ActorSystem("someName", ConfigFactory.load(cl), cl)</code> and not touching the context class loader, which seems somewhat cleaner (and less frightening to someone like me who does not know what the context class loader is or does)</p> <p><strong>TL;DR</strong> Instead of</p> <pre><code>val system = ActorSystem() </code></pre> <p>write</p> <pre><code>val cl = getClass.getClassLoader val system = ActorSystem("mySystem", ConfigFactory.load(cl), cl) </code></pre>

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