How to get value of the projected field from MongoDB document using java driver?

Question

I have a nested MongoDB document as shown below:

{
    "product_id": "123",
    "properties": {
      "Category": {
        "type": "object",
        "Electronics": {
          "type": "object",
          "Mobile": {
            "type": "string"
          },
          "Laptop": {
            "type": "string"
          }
        },
        "Clothing":{
            "type":"object",
            "Men":{
                "type":"string"
            },
            "women":{
                "type":"string"
            }
        }
      },
      "_id": {
        "type": "string"
      },
      "internal":{
        "type":"object",
        "hsn":{
            "type":"string"
        },
        "asr":{
            "type":"int"
        }
      }
    }
}

We have a collection of such documents where the product_id is unique. For a give product_id we have to return the type of a given property. For example: Return the type of category.electronics.mobile for product_id : 123. In this case output will be returned as "String". There can be any number of properties and can have any nested level.

I am trying to use this code to fetch the result:

FindIterable<Document> hierarchialResults = database.getCollection("test").find(Filters.and(
            eq("product_id", "123")
        )).projection(fields(include("category.electronics.mobile.type")));

But the above code gives me a document with key properties and when I do a get("properties") then it again returns a document with key "category" and when I get("category") then it returns a document with key ("Electronics") and it continues. I just want the type of my nested property passed and don't want to iterate again and again.

How to do this? Please share example in context with mongodb-java-driver.