private static ClassLoader resolveClassLoader(
      Map<String, ClassLoader> classLoaders,
      List<String> seen,
      Map<String, Classpath> classpaths,
      String id)
      throws MalformedURLException {
    if (classLoaders.containsKey(id)) {
      return classLoaders.get(id);
    }
    if (seen.contains(id)) {
      throw new ConfigurationException(MessageNames.CIRCULAR_CLASSPATH, id);
    }
    // Add the id to the list of classloaders we have attempted to build.
    seen.add(id);
    Classpath classpath = classpaths.get(id);
    if (classpath == null) {
      throw new ConfigurationException(MessageNames.CLASSPATH_UNDEFINED, id);
    }
    String parentClasspathId = classpath.getParent();
    ClassLoader parentClassLoader = null;
    if (parentClasspathId != null && !Strings.EMPTY.equals(parentClasspathId)) {
      parentClassLoader = resolveClassLoader(classLoaders, seen, classpaths, parentClasspathId);
    } else {
      /* Should be the 'extension' classloader. */
      parentClassLoader = Bootstrap.class.getClassLoader().getParent();
    }
    URL[] classpathUrls;
    classpathUrls = findClasspathURLS(classpath.getValue());

    SettableCodebaseClassLoader classLoader =
        new SettableCodebaseClassLoader(classpathUrls, parentClassLoader);
    classLoaders.put(id, classLoader);
    log.log(
        Level.FINE,
        MessageNames.CONFIGURED_CLASSPATH,
        new Object[] {id, Utils.format(classpathUrls)});
    seen.remove(id);
    return classLoader;
  }
  private static Map<String, ClassLoader> createClassLoaders(ContainerConfig config)
      throws MalformedURLException {

    Map<String, ClassLoader> classLoaders = new HashMap<String, ClassLoader>();
    classLoaders.put(Strings.BOOTSTRAP_CLASS_LOADER, Bootstrap.class.getClassLoader());
    /*
    Setup the classloaders according to the config file.
    */
    List<String> seen = new LinkedList<String>();
    Map<String, Classpath> classpaths = new HashMap<String, Classpath>();
    for (Classpath classpath : config.getClasspath()) {
      if (classpaths.containsKey(classpath.getId())) {
        throw new ConfigurationException(MessageNames.DUPLICATE_CLASSPATH, classpath.getId());
      }
      classpaths.put(classpath.getId(), classpath);
    }

    for (String id : classpaths.keySet()) {
      resolveClassLoader(classLoaders, seen, classpaths, id);
    }
    return classLoaders;
  }
 private Classpath createClasspathWithTwoElements() {
   return Classpath.emptyClasspath()
       .addClassPathElementUrl(FIRST_ELEMENT)
       .addClassPathElementUrl(SECOND_ELEMENT);
 }
 public void testReadFromPropertiesWithEmptyProperties() throws Exception {
   Classpath recreatedClasspath = readClasspathFromProperties();
   assertTrue(recreatedClasspath.getClassPath().isEmpty());
 }