docs: @SuppressWarnings("unchecked")
      protected List<Class<ApplicationContextInitializer<ConfigurableApplicationContext>>>
              determineContextInitializerClasses(PortletContext portletContext) {
          String classNames = portletContext.getInitParameter(CONTEXT_INITIALIZER_CLASSES_PARAM);
          List<Class<ApplicationContextInitializer<ConfigurableApplicationContext>>> classes =
              new ArrayList<Class<ApplicationContextInitializer<ConfigurableApplicationContext>>>();
          if (classNames != null) {
              for (String className : StringUtils.tokenizeToStringArray(classNames, ",")) {
                  try {
                      Class<?> clazz = ClassUtils.forName(className, ClassUtils.getDefaultClassLoader());
                      Assert.isAssignable(ApplicationContextInitializer.class, clazz,
                              "class [" + className + "] must implement ApplicationContextInitializer");
                      classes.add((Class<ApplicationContextInitializer<ConfigurableApplicationContext>>)clazz);
                  }
                  catch (ClassNotFoundException ex) {
                      throw new ApplicationContextException(
                              "Failed to load context initializer class [" + className + "]", ex);
                  }
              }
          }
          return classes;
      }