In Gson, how do I add a JsonArray to a JsonObject?

Question

Suppose that I am trying to get a Json structure like this:

{
  "rows": [
    {
      "date_str": "2016-07-01",
      "sleep_7_or_more_hours": true,
      "activity_minutes": "0",
      "water_5_or_more_cups": true,
      "fruit_veg_4_or_more_servings": true,
      "physical_activity_description": "walking"
    }
    {
      "date_str": "2016-07-02",
      "sleep_7_or_more_hours": true,
      "activity_minutes": "30",
      "water_5_or_more_cups": true,
      "fruit_veg_4_or_more_servings": true,
      "physical_activity_description": "walking"
    }  
    ...etc  
  ]
}

Some questions about building this Json:

1. How can I specify the name of the JsonArray ? I need it to be named, in the Json, "rows" .
2. How can I add the JsonArray rows to a JsonObject (I assume that's what the outer brackets mean)?

This is the code that I am using to do it:

JsonArray rows = new JsonArray();

//Code to get local dates omitted
for (LocalDate date = start; !date.isAfter(end); date = date.plusDays(1))
{
    JsonObject row = new JsonObject();

    DateTimeFormatter formatter = DateTimeFormatter.ofPattern("yyyy-mm-dd", Locale.ENGLISH);
    String dateString = date.format(formatter);
    row.addProperty("date_str", dateString);

    boolean sleptLongEnough = (sleepLog.getTimeInBed(getDate(date)) > (7 * 60));
    row.addProperty("sleep_7_or_more_hours", sleptLongEnough);

    int activityMinutes = (activitiesLog.getMinutesVeryActive(getDate(date)) + activitiesLog.getMinutesFairlyActive(getDate(date)));
    ...
    //Omitted extra code
    rows.add(row);
}
JsonObject logs = new JsonObject();
//add rows to logs here.

I need to add rows to logs . However, JsonObject only appears to have .add(JsonElement) and .addProperty(String, variousTypes) , and nothing to add an array. What am I missing?

EDIT: I am not using Gson to serialize objects because the Json is composed of data items from each of several logs (and not even close to all of the information in each log).

Answer 1

JsonArray is an instance of JsonElement . So the method .add("name", element) , where element is a JsonArray , should just work.

Answer 2

You can use the method JsonObject.add() to add a JsonElement , which JsonArray inherits from:

logs.add("rows", rows)

And then when deserializing it out, you can just cast it back to a JsonArray