apollo-core/src/main/java/com/ctrip/framework/apollo/core/utils/PropertiesUtil.java/PropertiesUtil/toString
class PropertiesUtil:  public static String toString(Properties properties) throws IOException {
    StringWriter writer = new StringWriter();
    properties.store(writer, null);
    StringBuffer stringBuffer = writer.getBuffer();
    filterPropertiesComment(stringBuffer);
    return stringBuffer.toString();
  }