JSON parsing to Java - Android application

Question

I need help with parsing json string in Java Android Appl.

Text of JSON file:

{"data":{"columns":["location_id","name","description","latitude","longitude","error","type","type_id","icon_media_id","item_qty","hidden","force_view"],"rows":[[2,"Editor","",43.076014654537,-89.399642451567,25,"Npc",1,0,1,"0","0"],[3,"Dow Recruiter","",43.07550842555,-89.399381822662,25,"Npc",2,0,1,"0","0"] [4,"Protestor","",43.074933,-89.400438,25,"Npc",3,0,1,"0","0"],[5,"State Legislator","",43.074868061524,-89.402136196317,25,"Npc",4,0,1,"0","0"],[6,"Marchers Bascom","",43.075296413877,-89.403374183615,25,"Node",22,0,1,"0","0"] [7,"Mary","",43.074997865584,-89.404967573966,25,"Npc",7,0,1,"0","0"]]},"returnCode":0,"returnCodeDescription":null}

How can get values: location_id, name, latitude, longitude. Thanks, Michal.

Answer 1

If you mean to navigate easily the Json Tree, you can use JSON Path, that is query system, similar to XPath to XML, that you can use to pick some elements in a json tree using text expressions.

http://code.google.com/p/json-path/ That's a good implementation

If you just mean that you want to parse that JSon you can use Gson from google (that is compatible with Android I guess).

Answer 2

You need to use the GSON lib http://code.google.com/p/google-gson/

Object Examples

class BagOfPrimitives {
  private int value1 = 1;
  private String value2 = "abc";
  private transient int value3 = 3;
  BagOfPrimitives() {
    // no-args constructor
  }
}

(Serialization)

BagOfPrimitives obj = new BagOfPrimitives();
Gson gson = new Gson();
String json = gson.toJson(obj);  
==> json is {"value1":1,"value2":"abc"}

Note that you can not serialize objects with circular references since that will result in infinite recursion.

(Deserialization)

BagOfPrimitives obj2 = gson.fromJson(json, BagOfPrimitives.class);   
==> obj2 is just like obj

Answer 3

This contains a complete example for your case.

Answer 4

First of all, you need to know about Json parsing in android, so for that first read this: JSONObject, in that class, you will see the below methods:

1. getJSONArray(String name)
2. getJSONObject(String name)
3. getString(String name)

and many more methods to be used while implementing JSON parsing in android.

Update:

And if you are still confused then click on below link to have many examples available on web: Android JSON Parsing

Answer 5

Using manual parsing you can implement it like this:

            JSONArray  pages     =  new JSONArray(jsonString);
            for (int i = 0; i < pages.length(); ++i) {
                JSONObject rec = pages.getJSONObject(i);
                JSONObject jsonPage =rec.getJSONObject("page");
                String address = jsonPage.getString("url");
                String name = jsonPage.getString("name");
                String status =  jsonPage.getString("status");
}

in your case note that your outer elemnt data is type of JSONObject and then you have a JSONArray

mine json file:

[{"page":{"created_at":"2011-07-04T12:01:00Z","id":1,"name":"Unknown Page","ping_at":"2011-07-04T12:06:00Z","status":"up","updated_at":"2011-07-04T12:01:00Z","url":"http://www.iana.org/domains/example/","user_id":2}},{"page":{"created_at":"2011-07-04T12:01:03Z","id":3,"name":"Down Page","ping_at":"2011-07-04T12:06:03Z","status":"up","updated_at":"2011-07-04T12:01:03Z","url":"http://www.iana.org/domains/example/","user_id":2}}] 

note that mine starts from [, which means an array, but yours from { and then you have [ array inside. If you run it with a debugger, you can see exactly what´s inside your json objects.

There are also better approaches like:

1. Jackson
2. Jackson-JR (light-weight Jackson)
3. GSON

All of them can be used to convert Java Objects into their JSON representation. It can also be used to convert a JSON string to an equivalent Java object.