code: public String key(String keyName, String defaultKeyName) {
  
          String value = getMessages().key(keyName, getLocalizeParameters());
          if (value.startsWith(CmsMessages.UNKNOWN_KEY_EXTENSION) && CmsStringUtil.isNotEmpty(defaultKeyName)) {
              value = getMessages().key(defaultKeyName, getLocalizeParameters());
          }
          return CmsStringUtil.escapeHtml(value);
      }
docs: Returns the localized resource string for a given message key.<p>
  
  For a detailed parameter description, see {@link CmsJspStatusBean#key(String)}.<p>
  
  @param keyName the key for the desired string
  @param defaultKeyName the default key for the desired string, used if the keyName delivered no resource string
  @return the resource string for the given key