Parse dynamic number of objects in JSON array

Question

I'm trying to Parse some JSON formatted text, but i'm not quite sure how to handle a dynamic object name. I've been looking around on the web, and from what I can tell this is referred to as a dictionary or a MAP in java, however I cant quite figure out how to handle the dynamic length.

I've validated my JSON using http://jsonlint.com/, the code I am parsing is below.

{
"0": {
    "animal_name": "Yoshi",
    "animal_type": "Day Gecko",
    "animal_id": "1"
},
"1": {
    "animal_name": "Wigglesworth",
    "animal_type": "Bearded Dragon",
    "animal_id": "2"
},
"command": "login",
"owner_id": "1"

}

There are a few details at the start which is static, then animals are returned, and the number of animals is dynamic.

I can extract the first part (Command and Owner_ID), and I can extract the animals individually, but i'm not sure how to loop through the array of animals. I dont know how many animals there are, and if I try to refer to them dynamically it doenst compile.

This is the code I have used to grab animals from the object, I'm just struggling to make it dynamic. android json response key value, parsing

This is quite similar to another question I posted in IOS, so my solution is a little more developed but still not quite there. Parse nested JSON code in IOS

//parse the JSON header
JSONObject jo = new JSONObject(result);

//extract the owner id from the login response
owner_id=jo.getInt("owner_id");

//if the server throws an error, pass this back
if (!jo.isNull("error"))
{
    //store to global variable
    server_response=jo.getString("error");
}
else
{   //we only look for animals if a valid owner has logged in
    if (owner_id>0)
    {   //loop through the sub items.
        //HELP PLEASE: THE x<=5 needs to change to loop to the number of dictionary items in the JSONObject JO
        for(int x=0; x<=5; x++){
            //Extract each animal
            //HELP PLEASE: The jo.getJSONObject needs to get a dynamic item, but if I put x in here, it doesnt compile
            JSONObject animal = jo.getJSONObject("1");

            String animal_name = new String();
            String animal_type = new String();
            int animal_id = 0;

            //try and extract pets
            animal_name=animal.getString("animal_name");
            animal_type=animal.getString("animal_type");
            animal_id=animal.getInt("animal_id");

            //To Do: This code will overwrite each animal with the last. Need so store in an array.
            //get shared preferences object
            SharedPreferences prefs = a03_home_page.this.getSharedPreferences("my_app_name", Context.MODE_PRIVATE);

            //store the data
            prefs.edit().putString("animal_name", animal_name).commit();
            prefs.edit().putString("animal_type", animal_type).commit();
            prefs.edit().putInt("animal_id", animal_id).commit();

        }
    }
}

Lovis · Accepted Answer · 2014-03-31 07:56:56Z

0

Normally, I would recommend changing the JSON to use an Array.

{
"animals": [
  {
    "animal_name": "Yoshi",
    "animal_type": "Day Gecko",
    "animal_id": "1"
  },
  {
    "animal_name": "Wigglesworth",
    "animal_type": "Bearded Dragon",
    "animal_id": "2"
  }, {... more animals ...}
],
"command": "login",
"owner_id": "1"
}

Now, you could simply add the dynamic number of animals to the JSONArray "animals" and iterate over it using a for-loop and jsonArray.getJSONObject(i);

However, if you can't change the json to your purposes, you can iterate over the keys:

Iterator keys = json.keys();
while(keys.hasNext()){
   JSONObject animal = json.getJSONObject(keys.next());
  // do smth
}

the problem with this approach is, that you have to be careful with "command" and "owner_id", since that are no json objects. So you need some more logic in the while loop.

edited Mar 31, 2014 at 7:56

answered Mar 31, 2014 at 7:32

Lovis

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3 Comments

Nick Hardman Over a year ago

Hi. Iterating over the keys worked like a treat. I've posted the code below to help anyone else reading this thread. `animal_count=0; int ServerObjectCount=0; Iterator KeyLoop = jo.keys(); while(KeyLoop.hasNext()) { KeyLoop.next(); ServerObjectCount++; } //subtract the two items which are known not to be animals ServerObjectCount=ServerObjectCount-2;

Lovis Over a year ago

@NickHardman good to hear that. Feel free to accept this as the answer, then.

Nick Hardman Over a year ago

Thanks for your help. Changing the JSON as per your suggestion wasnt an option as this would have invalidated the iOS version code.

Community · Accepted Answer · 2017-05-23 10:26:02Z

0

You need to use :

 Gson gson = new Gson();
    Object o = gson.fromJson(str, Object.class);
    List keys = new ArrayList();
    Collection values = null;
    if (o instanceof Map) {
        Map map = (Map) o;
        keys.addAll(map.keySet()); // collect keys at current level in hierarchy
        values = map.values();
    } else if (o instanceof Collection) {
        values = (Collection) o;
    }
    System.out.println(keys);// [CDG, ORY, LBG]
    for (int i = 0; i < keys.size(); i++) {
        System.out.println(keys.get(i));
    }

As seen in this link

edited May 23, 2017 at 10:26

CommunityBot

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answered Mar 31, 2014 at 7:47

Tsunaze

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Comments

VairavelRajendran · Accepted Answer · 2014-06-09 11:33:39Z

0

String result=yourjsondata.toString();

First assign your json array like this

JSONArray jsar=new JSONArray(result);

then parse objects like this

for(int i=0;i<jsar.length;i++)
{
JSONObject jsobj=new JSONObject(jsar[i]);

String strcode=jsobj.get("code");

String strrate=jsobj.get("rate");

String strtitle=jsobj.get("title");

String strsubtitle=jsobj.get("subtitle");
}

answered Jun 9, 2014 at 11:33

VairavelRajendran

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