Add JsonArray data into ArrayList

Question

How do I add jsonArray data into an ArrayList of type Product.

I wrote a test class with dummy json data. The main class is as follows:

public class convertData {

        public static void main(String[] args) {

            List<ProductModel> myList = new ArrayList<>();

            JsonArrayBuilder arrayBuilder = Json.createArrayBuilder();
            JsonObject jsonObject1, jsonObject2, jsonObject3;


            jsonObject1 = Json.createObjectBuilder()
                    .add("id", 1)
                    .add("name", "Albany")
                    .add( "manufacture", "Albany Superior Low Gi Sliced Brown Seed Bread 700g")
                    .add("price", 15.49)
                    .add("category", "Food")
                    .add ("type", "Breads")
                    .add( "image", "data:image/jpeg;base64,/9j/4A" )
                    .build();

            jsonObject2 = Json.createObjectBuilder()
                    .add("id", 1)
                    .add("name", "Albany")
                    .add( "manufacture", "yuyyjjgyced Brown Seed Bread 700g")
                    .add("price", 15.49)
                    .add("category", "Food")
                    .add ("type", "Breads")
                    .add( "image", "data:image/jpeg;base64,/9j/4A" )
                    .build();

            jsonObject3 = Json.createObjectBuilder()
                    .add("id", 1)
                    .add("name", "Albany")
                    .add( "manufacture", "Albany Superior Low Gi Sliced Brown Seed Bread 700g")
                    .add("price", 15.49)
                    .add("category", "Food")
                    .add ("type", "Milk")
                    .add( "image", "data:image/jpeg;base64,/9j/4A" )
                    .build();


            arrayBuilder.add(jsonObject1);
            arrayBuilder.add(jsonObject2);
            arrayBuilder.add(jsonObject3);

            JSONArray jArray = (JSONArray) arrayBuilder; 

            if (jArray != null) { 

                for (int i=0;i<jArray.length();i++){ 
                    myList.add(jArray.get(i));
                }
            }

        }
    }

I then created a product model class as follows:

class ProductModel {

            private int id;
            private String name;
            private String manufacture;
            private Double price;
            private String category;
            private String type;
            private String image;
            // get and setters
            ...

I have searched for similar solution, but there were not helpful in a way.

The project is written using J2SE platform, and I only added the jar files for json.

The json data I am building looks something like these:

[
    {
        "id": 1,
        "name": "Albany",
        "manufacture": "Albany Superior Low Gi Sliced Brown Seed Bread 700g",
        "price": 15.49,
        "category": "Food",
        "type": "Breads",
        "image": "data:image/jpeg;base64,/9j/4..."
    },
    {
        "id": 2,
        "name": "Blue Ribbon",
        "manufacture": "Blue Ribbon Brown Plus Low Gi Bread 700g",
        "price": 13.99,
        "category": "Food",
        "type": "Breads",
        "image": "data:image/jpeg;base64,/9j/4AAQSkZ."
    },
    {
        "id": 3,
        "name": "Cheese",
        "manufacture": "Galbani Mozzarella Cheese 300g",
        "price": 49.99,
        "category": "Food",
        "type": "Cheese",
        "image": "data:image/octet-stream;base64,/9j/4AAQSkZJRg..."
    }
]

Answer 1

To be easier to get help, you should explain what libraries you are using. There is one link you have put there to an example that is using json-simple so I will assume you use it as well.

Although simple, this library seems to not be documented and just a very few examples out there. Also not that many futures in it (like the one that you are after: to convert the json into a Java object).

One valid option is to use a better documented library for JSON, like Jackson or GSON.

If you want to continue with this, you can write specific adapter to transform JsonObject to ProductModel. Or a more general adapter using reflection to transform JsonObject to a java bean class.

Answer 2

A few chnages needs to be done to make it run:

1. Add a constructor in ProductModel class that will accept JsonObject as argument:

   public ProductModel(JsonObject json) {
       super();
       this.id = json.getInt("id");
       this.name = json.getString("name");
       this.manufacture = json.getString("manufacture");
       this.price = Double.parseDouble(json.getJsonNumber("price").toString());
       this.category = json.getString("category");
       this.type = json.getString("type");
       this.image = json.getString("image");
   }
   

2. use JsonArray instead of JSONArray and pass build array to it:

   JsonArray jArray = arrayBuilder.build();
   

3. call newly created constructor in add method:

   if (jArray != null) { 
   
            for (int i=0;i<jArray.size();i++){ 
                myList.add(new ProductModel((JsonObject) jArray.get(i)));
            }
        }
   

Answer 3

You can convert each JsonObject individually into a ProductModel object by doing something like this:

new com.fasterxml.jackson.databind.ObjectMapper().readValue(jsonObject.toString(), ProductModel.class);

Then you can easily add these objects into ProductModel type array.