apollo-client/src/main/java/com/ctrip/framework/apollo/internals/SimpleConfig.java/SimpleConfig/getProperty
class SimpleConfig:  @Override
  public String getProperty(String key, String defaultValue) {
    if (m_configProperties == null) {
      logger.warn("Could not load config from Apollo, always return default value!");
      return defaultValue;
    }
    return this.m_configProperties.getProperty(key, defaultValue);
  }