Insert Array inside an object in MongoDB

Question

I am new at MongoDB and I want to insert to mongodb data like this but I couldn\'t figure out how

{
  image = \"cab\"
  tags = [
            [ \"NNP\", 0 ],
             


        

Answer 1

Basically you use BasicDBObject for key-value mappings and BasicDBList for array objects. For the object in your question, you'd do this:

BasicDBList dbl = new BasicDBList();
dbl.add(new BasicDBObject("NNP",0));
dbl.add(new BasicDBObject("NN", 1));
BasicDBOBject outer=new BasicDBObject("image", "cab").append("tags", dbl);

There's some convenience methods in the api to make this a bit less verbose.

The mapping works like this:

for:  {"A":1}  use: new BasicDBObject("A",1)
for: {"A":1, "B":2}  use: new BasicDBObject("A",1).append("B",2)
for: {"A":{"B":2}}  use: new BasicDBObject("A",new BasicDBObject("B",2))
for: {"A":["B","C"]} use:
        BasicDBList dbl = new BasicDBList();
        dbl.add("B");
        dbl.add("C");
         ->  new BasicDBObject("A",dbl);

Answer 2

Here is how i use it when using mongo3.x:

suppose you want the result to be like this: {"data": [{"key":"v1"}, {"key":"v1"}, {"key":"v1"}] }

[step1]: use Java Map to create json object which maps to the elements inside the array; that is, the {} inside []

[step1 Ans]: Map m1,m2,m3 = new HashMap(); m1.put("key", "v1"); m2.put("key", "v1"); m3.put("key", "v1");

[step2]: use Java List to add all Java Map into one element.

[step2 Ans]: List list = new ArrayList(); list.add(m1); list.add(m2); list.add(m3);

[step3]: add Java list into mongo

[step3 Ans]: Document dc = new Document("key", list);

Answer 3

Did you mean like this?

    BasicDBObject obj = new BasicDBObject();
    obj.put("image", ....);
    for(Tag tag:tags){
        BasicDBObject tagsObj = new BasicDBObject();
        tagsObj.put("NNP",tag.getNNP());
        tagsObj.put("NN",tag.getNN());
        obj.put("tags",tagsObj);
    }