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javamongodbmongodb-querymongo-java-driver

Implementing Mongodb query using $elemMatch in Java


I am using Mongo java driver to retrieve data from mongo collections. I have the following query which I am trying to implement in java: Json is:

{
    "_id" : ObjectId("56cd284767c74d3d4dd3ec80"),
    "comments" : "Hello",
    "statusLog" : [ 
        {
            "status" : "Submitted",
            "startDate" : ISODate("2015-01-14T05:00:00.000Z"),
            "endDate" : ISODate("2016-02-29T21:24:24.740Z")
        }, 
        {
            "status" : "Active",
            "startDate" : ISODate("2016-02-29T21:24:24.740Z")
        }
    ],
    "createdDate" : ISODate("2015-01-14T05:00:00.000Z")
}

Mongo Query:

db.CollectionName.find({},{_id: 0, createdDate:1, "statusLog": {$elemMatch: {"status":"Submitted"}}});

Here is the query in java that I have written (mongo java driver 3.4.2):

BasicDBObject query = new BasicDBObject(new BasicDBObject("statusLog",
                new BasicDBObject("$elemMatch", new BasicDBObject("status", "Submitted"))));

Running the java code returns all status logs and not the one that I am looking for.

Any help would be highly appreciated.


Solution

  • elemMatch should be in find method not in projection bson. For example:

    collection.find(elemMatch("statusLog", eq("status", "Submitted"))).projection(projection);