How to append new value to a list in mongodb?

Question

I want to insert a new element the "CarList" array below. I am using MongoDB and dropwizzard in my project.

{
    "_id": "56aa6119bf78f37eee64697e",
    "name": "Jack",
    "occupation": "business*emphasized text* owner",
    "carList": [{
        "brand": "Ford",
        "cost": "$25000"
    }, {
        "brand": "Mazda",
        "cost": "$23000 "
    }]
}

My POJO classes:

public class CarOwners {

    @ObjectId
    public String _id;
    public String name;
    public String occupation;
    public List<CarDetails> carList;
}

public class CarDetails
{
    public String brand;
    public String cost;
}

My code to append a new entry in carList:

CarDetails newCarInfo = new CarDetails();
newCarInfo.brand="Toyota";
newCarInfo.cost="$20000";

BasicDBObject ownerQuery = new BasicDBObject("name", "Jack");
carOwnerCollections.update(ownerQuery, new BasicDBObject("$addToSet", new BasicDBObject("carList",newCarInfo)));

The error that I am getting:

org.codehaus.jackson.map.JsonMappingException: Can not instantiate value of type [simple type, class data.CarDetails] from JSON String; no single-String constructor/factory method (through reference chain: data.PropertyLedger["carList"])

From the error I can guess that the the wiring to CarDetails class is the issue. I am not sure how to solve it. I have looked in updating nested documents in Mongo and similar links but could not find an answer.

Any pointers will be helpful. Thank you.

Answer 1

Try doing it using the $push operator for arrays in MongoDB.

BasicDBObject ownerQuery = new BasicDBObject("name", "Jack");
//Below code will insert the new object to the existing carList array
carOwnerCollections.update(ownerQuery, new BasicDBObject("$push", new BasicDBObject("carList",new BasicDBObject("brand","Toyota").append("cost","$20000"))));