code: protected void checkParameters() {
          // 检查注入的ref是否接口实现类
          Class proxyClass = providerConfig.getProxyClass();
          String key = providerConfig.buildKey();
          T ref = providerConfig.getRef();
          if (!proxyClass.isInstance(ref)) {
              throw ExceptionUtils.buildRuntime("provider.ref",
                  ref == null ? "null" : ref.getClass().getName(),
                  "This is not an instance of " + providerConfig.getInterfaceId()
                      + " in provider config with key " + key + " !");
          }
          // server 不能为空
          if (CommonUtils.isEmpty(providerConfig.getServer())) {
              throw ExceptionUtils.buildRuntime("server", "NULL", "Value of \"server\" is not specified in provider" +
                  " config with key " + key + " !");
          }
          checkMethods(proxyClass);
      }
docs: for check fields and parameters of consumer config