docs: protected Class<?> determineContextClass(PortletContext portletContext) {
          String contextClassName = portletContext.getInitParameter(CONTEXT_CLASS_PARAM);
          if (contextClassName != null) {
              try {
                  return ClassUtils.forName(contextClassName, ClassUtils.getDefaultClassLoader());
              }
              catch (ClassNotFoundException ex) {
                  throw new ApplicationContextException(
                          "Failed to load custom context class [" + contextClassName + "]", ex);
              }
          }
          else {
              contextClassName = defaultStrategies.getProperty(PortletApplicationContext.class.getName());
              try {
                  return ClassUtils.forName(contextClassName, PortletContextLoader.class.getClassLoader());
              }
              catch (ClassNotFoundException ex) {
                  throw new ApplicationContextException(
                          "Failed to load default context class [" + contextClassName + "]", ex);
              }
          }
      }