public void query2(){

        String mondburl = Config.getInstance().getProperty("mongodb.host");

        MongoClientOptions options = new MongoClientOptions.Builder().socketKeepAlive(true).build();

        Mongo  client = new MongoClient(mondburl,  options);

        DB database = client.getDB("pnr");

        DBCollection coll = database.getCollection("b_dep_pnr_flt_test");

        DBObject keys = new BasicDBObject();

//条件

        DBObject dbObject = new BasicDBObject();

        dbObject.put("alnCd",  "CZ");

        dbObject.put("fltNr",  "3452");

        dbObject.put("fltDt",  "20180425000000");

        dbObject.put("arvCd",  "SZX");

        dbObject.put("depCd",  "LJG");

        DBObject initial = new BasicDBObject("dcsTimestamp", "0");

        String reduce = "function(doc,prev){" +

                "var docDcsTimestamp=doc.dcsTimestamp;" +

                "var prevDcsTimestamp=prev.dcsTimestamp;" +

                "var docDcsTimestampInt=parseInt(docDcsTimestamp);" +

                "var prevDcsTimestampInt=parseInt(prevDcsTimestamp);" +

                "if(docDcsTimestampInt > prevDcsTimestampInt){" +

                "prev.fltNr=doc.fltNr;" +

                "prev.fltDt=doc.fltDt;" +

                "prev.dcsTimestamp=doc.dcsTimestamp;}" +

                "}";

        BasicDBList dbList = (BasicDBList) coll.group(keys, dbObject, initial, reduce);

        //Iterator<Object> iterator = dbList.iterator();

//        for (Object object : dbList) {

//            System.out.println(((DBObject)object).toString());

//        }

        for (Object object : dbList) {

           BasicDBObject a  = (BasicDBObject) object;

           System.out.println(a.get("fltNr"));

        }

    }
    

    public static MongoClient mongoClient;

    public static Mongo mongo;

    private Object object;

    public static MongoClient connect() {

        String mondburl = Config.getInstance().getProperty("mongodb.host");

        MongoClientOptions options = new MongoClientOptions.Builder().socketKeepAlive(true).build();

        if(mongoClient == null) {

            mongoClient = new MongoClient(mondburl,  options);

        }

        return mongoClient;

    }