DriverManager 查询数据库拼接BUFFER

        Connection conn = null;
        Statement stmt = null;
        ResultSet rs = null;
        try{
            Class.forName("com.mysql.jdbc.Driver");
             String dbNmae = "logall"+params.get("dbName");
             String dbIp = ConfigUtil.pro.get("linkLogIp").toString();
             String linkCloudSql = "jdbc:mysql://"+dbIp+"/"+dbNmae;
             String linkCloudUsername =ConfigUtil.pro.get("linkLogIpUsername").toString();
             String linkCloudPassword =ConfigUtil.pro.get("linkLogIpPassword").toString();

             conn = DriverManager
                     .getConnection(
                             linkCloudSql,linkCloudUsername, linkCloudPassword);
             stmt = conn.createStatement();
             PreparedStatement ps=null;

             StringBuffer buffer = new StringBuffer("SELECT `id`,`idc`,`flag`,`cmdStartTime`,`json`,`cmdEndTime`,`retValue`,`crmId`,CASE WHEN `fName` = ‘‘ OR `fName` IS NULL THEN `idsid` ELSE `fName` END `fName`,`insertTime`,TIMESTAMPDIFF(FRAC_SECOND,cmdstarttime,cmdendtime )  AS duration FROM  log_controlresult  WHERE idc = ? and flag in (‘BlueToothControl‘,‘carControlNew‘)");
             if(params.get("ret") != null && StringUtils.isNoneEmpty(params.get("ret").toString())){
                 buffer.append("and retValue=?");
             }
             buffer.append(" order by crmid desc");
             buffer.append(" LIMIT "+params.get("startIndex")+","+params.get("pageSize"));

             ps=(PreparedStatement) conn.prepareStatement(buffer.toString());
              ps.setString(1, params.get("idc").toString());

              if(params.get("ret") != null && StringUtils.isNoneEmpty(params.get("ret").toString())){
                 ps.setString(2, params.get("ret").toString());
             }

             log.info("控制历史sql:"+buffer.toString());
              rs = ps.executeQuery();
             while(rs.next())
             {
                 controlresult cresult = new controlresult();
                 cresult.setId(rs.getLong("id"));
                 cresult.setIdc(rs.getString("idc"));
                 cresult.setFlag(rs.getString("flag"));
                 cresult.setCmdStartTime(rs.getTimestamp("cmdStartTime"));
                 cresult.setJson(rs.getString("json"));
                 cresult.setCmdEndTime(rs.getTimestamp("cmdEndTime"));
                 cresult.setRetValue(rs.getString("retValue"));
                 cresult.setCrmId(rs.getLong("crmId"));
                 cresult.setfName(rs.getString("fName"));
                 cresult.setInsertTime(rs.getTimestamp("insertTime"));
                 cresult.setDuration(rs.getInt("duration"));
                 cresult.setCmdName(GetSendTypeNameByJson(cresult.getJson()));
                 resultList.add(cresult);
             }
        }