private static Map<String, String> convertAttachment(TpURL tpUrl, String[] keys) {
		if (keys == null || keys.length == 0) {
			return null;
		}
		Map<String, String> attachment = new HashMap<String, String>();
		for (String key : keys) {
			String value = tpUrl.readParam(key);
			if (value != null && value.length() > 0) {
				attachment.put(key, value);
			}
		}
		return attachment;
	}