Mongodb mapreduce java 操做

mongodb數據庫中數據一覽：

有多條個cust_id數據，現統計cust_id爲abc124用戶items下sl爲0.17和0.13分別的總和是多少

java代碼以下：

MongoClient mongoClient = new MongoClient("192.168.1.45", 27017);
MongoCollection mongoCollection = mongoClient.getDatabase("tt").getCollection("tt");
String mapFunction = "function(){\n" +
        "for(var i = 0; i < this.items.length; i++){\n" +
        "var key = this.items[i].sl;\n" +
        "var value = {\n" +
        "count:1,\n" +
        "je: this.items[i].je,\n" +
        "se: this.items[i].se\n" +
        "};\n" +
        "emit(key, value);\n" +
        "}};\n";
String reduceFunction = "function(key,values){\n" +
        "reduceVal = {je:0,se:0};\n" +
        "for(var i = 0; i < values.length; i++){\n" +
        "reduceVal.je += values[i].je;\n" +
        "reduceVal.se += values[i].se;\n" +
        "}\n" +
        "return reduceVal;};\n";


JSONObject query = new JSONObject();
query.put("cust_id", "abc124");//設置查詢條件
Document queryDoc = Document.parse(query.toString());
MapReduceIterable mri = mongoCollection.mapReduce(mapFunction, reduceFunction).filter(queryDoc);
MongoCursor mongoCursor = mri.iterator();
JSONArray jsonArray = new JSONArray();
while (mongoCursor.hasNext()){
    JSONObject object = JSON.parseObject(((Document) mongoCursor.next()).toJson().toString());
    JSONObject jsonObject = new JSONObject();
    String sl = object.getString("_id");
    object.put("sl", sl);
    object.remove("_id");
    jsonArray.add(object);
}
System.out.println(jsonArray);

想要的功能已經實現，舊版的mongodb的mapreduce方法以下：

DBObject query = new BasicDBObject();
query.put("cust_id", "abc124");
Mongo mongo = new Mongo("192.168.1.45", 27017);
DB db = mongo.getDB("tt");
DBCollection collection = db.getCollection("tt");
MapReduceCommand mapReduceCommand =
        new MapReduceCommand(collection, mapFunction, reduceFunction, null, MapReduceCommand.OutputType.INLINE, query);
MapReduceOutput mapReduceOutput = collection.mapReduce(mapReduceCommand);
JSONArray jsonArray = new JSONArray();
for (DBObject o : mapReduceOutput.results()) {
    JSONObject jsonObject = JSON.parseObject(o.toString());
    String sl = jsonObject.getString("_id");
    jsonObject.put("sl", sl);
    jsonObject.remove("_id");
    jsonArray.add(jsonObject);
}
System.out.println(jsonArray);

固然咱們仍是推薦使用新版，官網參考：https://docs.mongodb.com/manual/tutorial/map-reduce-examples/