How to add elements in nested array in mongodb using java

Question

Hello all am working on mongodb with java, i have a scenario where if the outer document is matched then i have to update/add count in an nested array for eg i want to do something like this :

`"_id" : ObjectId("55d71603aed7562284e5df95"),
"id" : "1",
"type" : "a",
"score" : {
        "mark1" : "1",
        "mark2" : "2",
        "count" : { "one","two"                
        }
}`

if again i send a document with same fields like id:1, type:a,mark1:1,mark2:2 then i have to get my document as

`"_id" : ObjectId("55d71603aed7562284e5df95"),
"id" : "1",
"type" : "a",
"score" : {
        "mark1" : "1",
        "mark2" : "2",
        "count" : { "one","two","three"                
        }
}`

But i am getting some thing like this :

`"_id" : ObjectId("55d71e42aed7560e8c9d02e4"),
"id" : "1",
"type" : "a",
"score" : {
        "mark1" : "1",
        "mark2" : "2",
        "count" : {
                "count" : "one",

        }
}`

My java code is

 `mongoDatabase=mongoClient.getDatabase("TestNestedInsert");
        Document sourceDocument=mongoDatabase.getCollection("entity").find(new Document("id",1).append("score.mark1", "1").append("score.mark2", "2")).first();
        if(sourceDocument==null){
            Document entity=new Document();
            entity.append("id", "1");
            entity.append("type", "a");
            entity.append("score", new Document("mark1","1").append("mark2", "2").append("count", new Document("count","one")));
            mongoDatabase.getCollection("entity").insertOne(entity);
        }
        else{
            mongoDatabase.getCollection("entity").findOneAndUpdate(new Document("id",1).append("score.mark1", "1").append("score.mark2", "2"), new Document("$set",new Document("score.count","three")));
        }
        `

i know we cannot have duplicate keys i tried $set and $push as well but i am stuck. Any help ?

problem is you are "setting" the field with $set. You should push with $push operator. The $set operator replaces the value of a field with the specified value. The $push operator appends a specified value to an array. — rdllopes
– rdllopes, Commented Aug 21, 2015 at 13:04
No i am not able to do with $push either, i tried with both $set and $push. — Shaik Mujahid Ali
– Shaik Mujahid Ali, Commented Aug 21, 2015 at 13:08
It is not about "No, I am not able". You are. But, you should use an array. "count" filed is not array. That is why push is not working. stackoverflow.com/questions/10522347/… — rdllopes
– rdllopes, Commented Aug 21, 2015 at 13:19

Julian Espinel · Accepted Answer · 2015-12-28 16:19:57Z

The main issue is that, according to the code, the "count" key is an object not an array. So the correct JSON representation is:

{
    "_id": ObjectId("55d71603aed7562284e5df95"),
    "id": "1",
    "type": "a",
    "score": {
        "mark1": "1",
        "mark2": "2",
        "count": [
            "one",
            "two",
            "three"
        ]
    }
}

Note the square brackets "[]" after the "count" key.

I had the same question regarding the new mongo java driver (3.0). Here is how I solved it:

MongoDatabase mongoDatabase = mongoClient.getDatabase("TestNestedInsert");
MongoCollection<Document> entityCollection = mongoDatabase.getCollection("entity");

Document queryDocument = new Document("id", 1).append("score.mark1", "1").append("score.mark2", "2");
Document sourceDocument = entityCollection.find(queryDocument).first();

if (sourceDocument == null) {
    Document entity = new Document();
    entity.append("id", "1");
    entity.append("type", "a");

    // Create the score nested object
    String[] countArray = { "one", "two" }; // create the count array
    Document scoreObject = new Document()
            .append("mark1", "1")
            .append("mark2", "2")
            .append("count", countArray); // append the count array

    entity.append("score", scoreObject); // append the score object.
    entityCollection.insertOne(entity);
}
else{
    // push the new element to the count array.
    // see: https://docs.mongodb.org/v3.0/reference/operator/update/push/#append-a-value-to-an-array
    Document elementToArray = new Document("score.count", "three");
    Document pushElement = new Document("$push", elementToArray);
    entityCollection.updateOne(queryDocument, pushElement);
}

Hope it helps!

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