code: @Override
      public void init(String jsonString) throws AuthenticationException {
          try {
              setConfig(new JsonSimpleConfig(jsonString));
          } catch (UnsupportedEncodingException e) {
              throw new AuthenticationException(e);
          } catch (IOException e) {
              throw new AuthenticationException(e);
          }
      }
docs: Initialisation of Internal Authentication plugin
  
  @throws AuthenticationException if fails to initialise