public QueryDownloadCmd(String group,String fileName) throws UnsupportedEncodingException {
		super();
		byte[] groupByte = group.getBytes(charset);
		int group_len = groupByte.length;
		if (group_len > FDFS_GROUP_NAME_MAX_LEN) {
			group_len = FDFS_GROUP_NAME_MAX_LEN;
		}
		byte[] fileNameByte = fileName.getBytes(charset);
		body1 = new byte[FDFS_GROUP_NAME_MAX_LEN + fileNameByte.length];
		Arrays.fill(body1, (byte) 0);
		System.arraycopy(groupByte, 0, body1, 0, group_len);
		System.arraycopy(fileNameByte, 0, body1, FDFS_GROUP_NAME_MAX_LEN, fileNameByte.length);
		this.requestCmd = TRACKER_PROTO_CMD_SERVICE_QUERY_FETCH_ONE;
		this.responseCmd = TRACKER_PROTO_CMD_RESP;
		this.responseSize = TRACKER_QUERY_STORAGE_FETCH_BODY_LEN;
	}