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POIs it possible to "reset" a class loader?
 

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    <p><strong>I have to dynamically load a class with the same name from some JAR, but different implementation, multiple times.</strong></p> <p>I'm creating an evaluator backend and I have to dynamically load classes and test them.</p> <p>The tests are JUnit classes that instantiate the classes which should be tested, this is a simple example:</p> <pre><code>package evaluator.tests; import static org.junit.Assert.*; import org.junit.*; import evaluator.tested.*; public class KTest { private K tested; @Before public void setup() { tested = new K(); } @Test public void returnsTrueTest() { assertTrue(tested.returnsTrue()); } } </code></pre> <p>The rest of my application would need to receive JAR files from users which would contain implementations of the <code>K</code> class which is being tested above. Then, <code>KTest</code> would have to run on <em>their</em> <code>K</code> classes, not the ones in the application.</p> <p>I know how to dynamically load a class, but I don't know how to make a test work with it, and not the one which I made.</p> <p>One of the solutions I came up with was to isolate testing in a completely new class, e.g. <code>Evaluation</code>, create a new <strong>class loader</strong> in that class, and make it load all referenced classes. After creating the class loader, it would load the <code>K</code> class from the JAR file.</p> <p>This would mean that each time a user submits his JAR, a separate <code>Evaluation</code> would be instantiated, it would create its own class loader and start the JUnit test. When that happens, the test would use the user's implementation of <code>K</code>, <em>and not the default one</em>.</p> <p><strong>Is this possible, and how can it be done?</strong></p> <p>I read that class loaders always ask their parent whether a class is already loaded. This would mean that I would have to somehow "flush" all the classes that I loaded dynamically from the JAR file in <code>Evaluation</code>, so that they would be unloaded and then loaded again in another <code>Evaluation</code>.</p> <p>Load class <code>K</code>, test class <code>K</code>, unload class <code>K</code>, repeat with different <code>K</code>.</p>
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