private String metaDataToStr(Map<String,String> metaData){
		StringBuffer sb = new StringBuffer();
		for(String key:metaData.keySet()){
			sb.append(FDFS_RECORD_SEPERATOR);
			sb.append(key);
			sb.append(FDFS_FIELD_SEPERATOR);
			sb.append(metaData.get(key));
		}
		
		return sb.toString().substring(FDFS_RECORD_SEPERATOR.length());
	}