@Override
    protected String doBuildColumnString(String dm) {
        StringBuilder sb = new StringBuilder();
        sb.append(dm).append(crawlingInfoId);
        sb.append(dm).append(createdTime);
        sb.append(dm).append(key);
        sb.append(dm).append(value);
        if (sb.length() > dm.length()) {
            sb.delete(0, dm.length());
        }
        sb.insert(0, "{").append("}");