Mongodb query for nested document in java

Question

I am new to Mongodb. I have the following dataset in mongodb.

{
"_id": {
    "$oid": "563644f44b17ca12886440a9"
},
"data": [
    {
        "uid": 1,
        "character": " ",
        "unicode": 32,
        "color": -7309587
    },
    {
        "uid": 2,
        "character": "!",
        "unicode": 33,
        "color": -8911704
    },
    {
        "uid": 3,
        "character": "\"",
        "unicode": 34,
        "color": -1778539
    }

I am trying to retrieve the color from this field using the _id and character. I am not able to execute the query.

This is what I tried.

DBObject clause1 = new BasicDBObject("_id",new ObjectId(KEY1));  
                DBObject clause2 = new BasicDBObject("data.character",text[i]);    
                BasicDBList or = new BasicDBList();
                or.add(clause1);
                or.add(clause2);
                DBObject query = new BasicDBObject("$and", or);

Also I am having a lot of issues in finding ways to query in mongodb-java for the 3.0.0+ api. Could someone please help?

As an output you just need data.color for a particular _id & data.character. Right? — Dev
– Dev, Commented Nov 2, 2015 at 5:20
then, I guess you need to unwind data array and using $match and $projection operator in aggregation you can achieve this. — Dev
– Dev, Commented Nov 2, 2015 at 5:45
Can you please try this on shell. If this works, you can easily convert in into corresponding Java Code: db.col1.aggregate([{$unwind:"$data"},{$match:{$and:[{"_id" : ObjectId("<your id here>")},{"data.character":" "}]}},{$project:{"data.color":1,"_id":0}}]) — Dev
– Dev, Commented Nov 2, 2015 at 5:52

Dev · Accepted Answer · 2015-11-02 08:59:24Z

1

    MongoClient mongoClient = new MongoClient(new ServerAddress("localhost", 27017));
    MongoDatabase db = mongoClient.getDatabase("testDB");
    AggregateIterable<Document> iterable = db.getCollection("testCollection").aggregate(
            asList(new Document("$unwind", "$data"), new Document("$match", (new Document("_id", new ObjectId(
                    "5636f106b2acf98ecb033b98")).append("data.character", " "))), new Document("$project",
                    new Document("data.color", 1).append("_id", 0))));

    iterable.forEach(new Block<Document>()
    {
        @Override
        public void apply(final Document document)
        {
            System.out.println(document.toJson());
        }
    });

For more details check MongoDB Documentation.

answered Nov 2, 2015 at 8:59

Dev

13.8k24 gold badges90 silver badges189 bronze badges

Sign up to request clarification or add additional context in comments.

1 Comment

Amriteya Over a year ago

I got this. I was facing a lot of trouble with aggregate method of collection. I was using the 3.0.0 java-mongo driver api. Apparently, they have changed it a lot and it's still in beta. Thank you so much.

Clement Amarnath · Accepted Answer · 2015-11-02 05:57:07Z

0

A simple solution

In your document, oid is an unique key for each document and hence your query should be like this

  DBObject query = new BasicDBObject("_id.oid", KEY1);
  // Query with value - DBObject query = new BasicDBObject("_id.oid","563644f44b17ca12886440a9");

  Assign this to a cursor as shown below
  DBCollection coll = db.getCollection("mycollection");
  DBCursor cursor = coll.find(query);
  Iterate the collection and retrieve your desired value.

answered Nov 2, 2015 at 5:57

Clement Amarnath

5,4761 gold badge23 silver badges34 bronze badges

1 Comment

Amriteya Over a year ago

I am getting the id by _id also.

Collectives™ on Stack Overflow

Mongodb query for nested document in java

2 Answers 2

1 Comment

1 Comment

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

1 Comment

1 Comment

Your Answer

Sign up or log in

Post as a guest

Related