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copied!<p>If you used the custom <code>ClassLoader</code> exactly like in the linked answer it is not overriding the method <code>protected Class<?> loadClass(String name, boolean resolve)</code>. This implies that when the JVM is resolving dependencies it will still delegate to the parent class loader. And, of course, when it was not delegating to the parent <code>ClassLoader</code> it had the risk of missing some required classes.</p> <p>The easiest solution is to set up the right parent class loader. You are currently passing <code>Thread.currentThread().getContextClassLoader()</code> which is a bit strange as your main intention is that the delegation should <em>not</em> delegate to that loader but load the changed classes. You have to think about which class loaders exist and which to use and which not. E.g. if the class <code>Foo</code> is within the scope of your current code but you want to (re)load it with the new ClassLoader, <code>Foo.class.getClassLoader().getParent()</code> would be the right delegate parent for the new <code>ClassLoader</code>. Note that it might be <code>null</code> but this doesn’t matter as in this case it would use the bootstrap loader which is the correct parent then.</p> <p>Note that when you set up the right parent <code>ClassLoader</code> matching your intentions you don’t need that custom <code>ClassLoader</code> anymore. The default implementation (see <a href="http://docs.oracle.com/javase/7/docs/api/java/net/URLClassLoader.html" rel="noreferrer"><code>URLClassLoader</code></a>) already does the right thing. And with current Java versions it is <code>Closeable</code> making it even more suitable for dynamic loading scenarios.</p> <p>Here is a simple example of a class reloading:</p> <pre><code>import java.io.IOException; import java.net.URL; import java.net.URLClassLoader; public class ReloadMyClass { public static void main(String[] args) throws ClassNotFoundException, IOException { Class<?> myClass=ReloadMyClass.class; System.out.printf("my class is Class@%x%n", myClass.hashCode()); System.out.println("reloading"); URL[] urls={ myClass.getProtectionDomain().getCodeSource().getLocation() }; ClassLoader delegateParent = myClass.getClassLoader().getParent(); try(URLClassLoader cl=new URLClassLoader(urls, delegateParent)) { Class<?> reloaded=cl.loadClass(myClass.getName()); System.out.printf("reloaded my class: Class@%x%n", reloaded.hashCode()); System.out.println("Different classes: "+(myClass!=reloaded)); } } } </code></pre>

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