如何在Mongodb java驱动程序中编写多个group by id字段

Question

在下面的查询中

{ $group : {
        _id :  { success:'$success', responseCode:'$responseCode', label:'$label'},
        max_timeStamp : { $timeStamp : 1 },
        count_responseCode : { $sum : 1 },
        avg_value : { $sum : "$value" },
        count_success : { $sum : 1 }
    }}

如何将id{success:'$success'，responseCode：'$responseCode'，label：'$label}，转换为在java mongodb驱动程序中使用。

我试过了

BasicDBList list = new BasicDBList();
list.add(new BasicDBObject("success", "$success"));
list.add(new BasicDBObject("responseCode", "$responseCode"));
list.add(new BasicDBObject("label", "$label"));
AggregationOutput output = collection.aggregate(match, project, group); 

和

多维数组

String [][] muitiGroupBy = {{"success", "$success"},{"responseCode", "$responseCode"},{"label", "$label"}};

等

但结果总是这样

"_id" : [ { "success" : "$success"} , { "responseCode" : "$responseCode"}]

如果我只使用一个字段，它就会工作。

DBObject groupFields=new BasicDBObject（“\u id”，new BasicDBObject（“success”，“$success”））；

Answer 1

我可以通过以下代码实现这一点（grails代码和mongo-java-driver-3.2）：

DBObject groupFields = new BasicDBObject()
groupFields.put('success', "\$success")
groupFields.put('responseCode', "\$responseCode")
groupFields.put('label', "\$label")
def result = collection.aggregate(Arrays.asList(Aggregates.group(groupFields, []))).iterator()

Answer 2

我也有类似的需求，在多次尝试将聚合操作转换为Java客户端可以处理的内容失败后，titogeo在2013年的回答引导我朝着正确的方向前进。这就是我使用的：

MongoCollection<Document> myCollection = myDB.getCollection("myCollection");

Map<String, Object> multiIdMap = new HashMap<String, Object>();
multiIdMap.put("groupField1", "$groupField1");
multiIdMap.put("groupField2", "$groupField2");

Document groupFields = new Document(multiIdMap);
AggregateIterable<Document> aggregate = myCollection.aggregate(Arrays.asList(
        Aggregates.group(groupFields,
                Accumulators.last("lastDate", "$dateCreated"),
                Accumulators.last("lastNumAvail", "$availableUnits")
                )
        ));

我得到了匹配结果所需的准确信息：

db.myCollection.aggregate([
            {"$group":{ "_id":{
                groupField1: "$groupField1", 
                groupField2: "$groupField2"}, 
                lastDate: 
                    {"$last":"$dateCreated"}, 
                lastNumAvail: 
                    {"$last":"$availableUnits"}
                }
               }                
            ]);

Answer 3

我们确实想出了办法。我们可以用这个来实现。

Map<String, Object> dbObjIdMap = new HashMap<String, Object>();
dbObjIdMap.put("success", "$success");
dbObjIdMap.put("responseCode", "$responseCode");
dbObjIdMap.put("label", "$label");
DBObject groupFields = new BasicDBObject( "_id", new BasicDBObject(dbObjIdMap));