How can I parse array of json objects using GSON into JAVA two-dimensional array?

Question

I Have such kind of JSON string:

[{
    "id": 3,
    "city": "Ilmenau",
    "floor": null,
    "housenumber": "35",
    "streetname": "Blumenstraße",
    "zip": "98693"
}, {
    "id": 4,
    "city": "Berlin",
    "floor": null,
    "housenumber": "54",
    "streetname": "Bogdansplatz",
    "zip": "194354"
}]

And I need it to be parsed into two-dimensional array that will look like this: enter image description here How can I make it, using GSON java library? Now I have only written this piece of code, that returns a list:

String s=getJson("SELECT * FROM address;");

        JsonParser jsonParser = new JsonParser();
        JsonObject jo = (JsonObject)jsonParser.parse(s);
        JsonArray jsonArr = jo.getAsJsonArray("array");
        //jsonArr.
        Gson googleJson = new Gson();
        ArrayList jsonObjList = googleJson.fromJson(jsonArr, ArrayList.class);
        System.out.println("List size is : "+jsonObjList.size());
        System.out.println("List Elements are  : "+jsonObjList.toString());

But the code above works only with JSON object of array, not with string I have shown above.

Sanjeev Saha · Accepted Answer · 2016-07-13 12:10:36Z

1

Could you please try the following and see the results:

// String 's' holds the JSON 

JsonParser jsonParser = new JsonParser();
JsonArray jsonArray = (JsonArray) jsonParser.parse(s);

// this object is used to get the keys
JsonObject firstJsonObject = jsonArray.get(0).getAsJsonObject();        
Set<java.util.Map.Entry<String, JsonElement>> entrySet = firstJsonObject.entrySet();

// declare two dimensional array
Object[][] array = new Object[entrySet.size()][jsonArray.size() + 1];

// the first column of the two-dimensional array is populated
Iterator<java.util.Map.Entry<String, JsonElement>> itr = entrySet.iterator();
for (int i = 0; itr.hasNext(); i++) {
    array[i][0] = itr.next().getKey();
}

// the rest of the columns are populated
for (int i = 0; i < jsonArray.size(); i++) {
    JsonObject obj = (JsonObject) jsonArray.get(i);
    for (int j = 0; j < array.length; j++) {
        String key = array[j][0].toString();
        JsonElement value = obj.get(key);
        array[j][i + 1] = value instanceof JsonNull ? null : value.getAsString();
    }

}
// now the two dimensional array is fully populated

edited Jul 13, 2016 at 12:10

answered Jul 13, 2016 at 10:45

Sanjeev Saha

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4 Comments

Bogdan Lashkov Over a year ago

Yes, I think it is a good idea, but after sql request I can get various fields name, but in your code they are already predestined. So may it is possible to make an array without predestined fields names?

Sanjeev Saha Over a year ago

Hi @BogdanLashkov could you please have a look at my edited answer?

Bogdan Lashkov Over a year ago

Hi @sanjeev-saha, thanks for help! As I can see, you added JsonElement to get string, so I have added a com.google.gson.JsonElement class. But now I have 2 exceptions: Error:(27, 9) java: cannot find symbol symbol: class Set location: class DynamicReports.hangling_json_try_2 Error:(33, 9) java: cannot find symbol symbol: class Iterator location: class DynamicReports.hangling_json_try_2 imgur.com/a/2KKWN

Bogdan Lashkov Over a year ago

I am a fool, I forgot to add import java.util.Iterator; import java.util.Map; import java.util.Set;

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