code: private void initAttrs(FilterConfig config){
  
          String param  = config.getInitParameter(SESSION_COOKIE_NAME);
          sessionCookieName = Strings.isNullOrEmpty(param) ? DEFAULT_SESSION_COOKIE_NAME : param;
  
          param = config.getInitParameter(MAX_INACTIVE_INTERVAL);
          maxInactiveInterval = Strings.isNullOrEmpty(param) ? DEFAULT_MAX_INACTIVE_INTERVAL : Integer.parseInt(param);
  
          cookieDomain = config.getInitParameter(COOKIE_DOMAIN);
  
          param = config.getInitParameter(COOKIE_CONTEXT_PATH);
          cookieContextPath = Strings.isNullOrEmpty(param) ? DEFAULT_COOKIE_CONTEXT_PATH : param;
  
          param = config.getInitParameter(COOKIE_MAX_AGE);
          cookieMaxAge = Strings.isNullOrEmpty(param) ? DEFAULT_COOKIE_MAX_AGE : Integer.parseInt(param);
  
          log.info("SessionFilter (sessionCookieName={},maxInactiveInterval={},cookieDomain={})", sessionCookieName, maxInactiveInterval, cookieDomain);
      }
docs: init basic attribute
  @param config the filter config