code: public void setKey(String key) {
          if (!isValidParamKey(key)) {
              throw ExceptionUtils.buildRuntime("param.key", key, "key can not start with "
                  + RpcConstants.HIDE_KEY_PREFIX + " and " + RpcConstants.INTERNAL_KEY_PREFIX);
          }
          this.key = key;
      }
docs: Sets key.
  
  @param key the key