apollo-client/src/main/java/com/ctrip/framework/apollo/internals/PlainTextConfigFile.java/PlainTextConfigFile/getContent
class PlainTextConfigFile:  @Override
  public String getContent() {
    if (!this.hasContent()) {
      return null;
    }
    return m_configProperties.get().getProperty(ConfigConsts.CONFIG_FILE_CONTENT_KEY);
  }