javax.json: Build a JSONArray from a List<Integer> and add it to a JSONObject

Question

Simple task but I couldn't find a way to do it.

My output JSON needs to be

{
   "id" : "somestring", 
   "nums" : [44,31,87,11,34]
}

I'm using the javax.json library with JSONObject / JsonArray . There is a List<Integer> which comes in with the values for the 2nd field. These aren't objects, these are plain numbers. I don't know how to get a JSONValue from an Integer.

        Map<String, Object> config = new HashMap<String, Object>();
        JsonBuilderFactory factory = Json.createBuilderFactory(config);
        JsonArray jsonArray = (JsonArray) Json.createArrayBuilder();
        for (Integer num: nums) // Assume a List<Integer> nums
            jsonArray.add(..); // What to do here? JSONValue from an Integer?
                               // Can't do jsonArray.add(num)

        // Final Object
        JsonObject value = factory.createObjectBuilder()
            .add("id", id)
            .add("nums", jsonArray); // Link up jsonArray to the 2nd Add

Note - can't add an Integer directly,

Answer 1

createArrayBuilder method will return JsonArrayBuilder object, you should not do the explicit type casting. So first create array builder and then add Integers to it

JsonArrayBuilder jsonArray = Json.createArrayBuilder();
    for (Integer num: nums) {
        jsonArray.add(num); 
      }

Then finally call build method that will build JsonArray

JsonArray array = jsonArray.build();

Answer 2

FINAL SOLUTION (thanks Deadpool )

        Map<String, Object> config = new HashMap<String, Object>();
        JsonBuilderFactory factory = Json.createBuilderFactory(config);
        JsonArrayBuilder jsonArrayBuilder = Json.createArrayBuilder();
        for (Integer num: nums) 
            jsonArrayBuilder.add(temp); // Note: adding to the Array Builder here

        // Now add to the final object
        JsonObject obj = factory.createObjectBuilder()
            .add("id", id)
            .add("nums", jsonArrayBuilder)  /* Note the Array Builder is passed in */
            .build();

        // The full object is complete now and can be printed
        // It looks like: { "id":"string", "nums":[4,6,1,2] }
        System.out.println("Object: \n" + obj.toString());

Answer 3

I see in your code that you are already using in the loop the Integer class which is an object-type wrapper of primitive type int . So the call jsonArray.add should work because num is an object and not a primitive type.

for (Integer num: nums) // Assume a List<Integer> nums
            jsonArray.add(num); 

Answer 4

Maybe you should try this code.

for(Integer num : nums)
   jsonArray.add(num.intValue());