apollo-core/src/main/java/com/ctrip/framework/foundation/internals/provider/DefaultApplicationProvider.java/DefaultApplicationProvider/getProperty
class DefaultApplicationProvider:  @Override
  public String getProperty(String name, String defaultValue) {
    if (ApolloClientSystemConsts.APP_ID.equals(name)) {
      String val = getAppId();
      return val == null ? defaultValue : val;
    }

    if (ApolloClientSystemConsts.APOLLO_ACCESS_KEY_SECRET.equals(name)) {
      String val = getAccessKeySecret();
      return val == null ? defaultValue : val;
    }

    String val = m_appProperties.getProperty(name, defaultValue);
    return val == null ? defaultValue : val;
  }