How to iterrate through Json Array and return each value

Question

I have a Json file that contains an Array of Json Objects:

[{"id":"939f0080-e93e-4245-80d3-3ac58a4a4335","name":"Micha","date":"2021-04-20T11:21:48.000Z","entry":"Wow"}, {"id":"939f0070-e93f-4235-80d3-3ac58a4a4324","name":"Sarah","date":"2021-04-21T11:21:48.000Z","entry":"Hi"}, {"id":"897f0080-e93e-4235-80d3-3ac58a4a4324","name":"John","date":"2021-04-25T17:11:48.000Z","entry":"Hi how are you"}...]

I'm using Json-simple to get the array, but I'm only able to get the object, but not the values.

JSONParser jsonParser = new JSONParser();

        try {
            FileReader reader = new FileReader("j.json");
            Object object = jsonParser.parse(reader);
            JSONArray jsonArray = (JSONArray) object;
            //prints the first Object
            System.out.println("element 1 is" +  jsonArray.get(0));
            
            //prints whole Array
            System.out.println(jsonArray);

how do i Iterate trough my file and get the values of each date, name date and entry instead of the object?

I want to get something like :

"id is 939f0080-e93e-4245-80d3-3ac58a4a4335 name is Micha date is 2021-04-20T11:21:48.000Z enry is wow"
"id is 939f0070-e93f-4235-80d3-3ac58a4a4324 name is Sarah 2021-04-21T11:21:48.000Z date is 2021-04-21T11:21:48.000Z"
"name is ..."

peterulb · Answer 1 · 2021-07-05T09:32:32.060

What you want is basically this

    public static void main(String[] args) {
        JSONParser jsonParser = new JSONParser();

        try (FileReader reader = new FileReader("j.json")) {
            Object object = jsonParser.parse(reader);
            JSONArray jsonArray = (JSONArray) object;
            for (Object o : jsonArray) {
                JSONObject jsonObject = (JSONObject) o;
                System.out.printf("id is %s name is %s date is %s entry is %s%n", jsonObject.get("id"), jsonObject.get("name"), jsonObject.get("date"), jsonObject.get("entry"));

                // Or if you want all
                for (Object key : jsonObject.keySet()) {
                    System.out.printf("%s is %s", key, jsonObject.get(key));
                }
                System.out.println();
            }
        } catch (IOException | ParseException e) {
            e.printStackTrace();
        }
    }

You can use getOrDefault in case the attribute is optional. There are also countless other libraries which can transform your json into a java object. This will give you more type safety. E.g. jackson or gson.

score 0 · Answer 2 · answered Jul 05 '21 at 09:16

JSONArray implements Collection and Iterable, so you can iterate over it with a For loop or using an Iterator or Stream. sadly, the object is not generic typed, so you will always get Objects and have to cast them yourself:

for(Object value : jsonArray) {
   // your code here //
}

score 0 · Answer 3 · answered Jul 05 '21 at 09:30

Hope this helps:

JSONParser jsonParser = new JSONParser();

try {
    Object object = jsonParser.parse("[{\"id\":\"939f0080-e93e-4245-80d3-3ac58a4a4335\",\"name\":\"Micha\",\"date\":\"2021-04-20T11:21:48.000Z\",\"entry\":\"Wow\"}, {\"id\":\"939f0070-e93f-4235-80d3-3ac58a4a4324\",\"name\":\"Sarah\",\"date\":\"2021-04-21T11:21:48.000Z\",\"entry\":\"Hi\"}, {\"id\":\"897f0080-e93e-4235-80d3-3ac58a4a4324\",\"name\":\"John\",\"date\":\"2021-04-25T17:11:48.000Z\",\"entry\":\"Hi how are you\"}]");
    JSONArray jsonArray = (JSONArray) object;

    jsonArray.forEach(x -> {
        JSONObject o = (JSONObject) x;
        String collect = o.entrySet()
                .stream()
                .map(e -> e.getKey() + " is " + e.getValue().toString())
                .collect(Collectors.joining(" "));
        System.out.println(collect);
    });
} catch (ParseException e) {
    e.printStackTrace();
}

How to iterrate through Json Array and return each value

3 Answers3