Can I dynamically unload and reload (other versions of the same) JAR?

Question

I am writing a server program which is used to run unit tests of an API (displaying lots of information and providing web access to control / monitor the whole thing)...<

Answer 1

You could programatically modify your classpath to reflect your JAR changes. Here is how I would do it:

  URLClassLoader urlClassLoader = (URLClassLoader) ClassLoader.getSystemClassLoader();
        Method m = URLClassLoader.class.getDeclaredMethod("addURL", new Class[]{URL.class});
        m.setAccessible(true);
        m.invoke(urlClassLoader, jarFile.toURI().toURL());
        String cp = System.getProperty("java.class.path");
        if (cp != null) {
            cp += File.pathSeparatorChar + jarFile.getCanonicalPath();
        } else {
            cp = jarFile.toURI().getPath();
        }
        System.setProperty("java.class.path", cp);

where jarFile is the version of the jar you want to use/overwrite.