Java Parse Json Array in another Json Array json.simple

Question

I'm using JSON.simple lib and try to parse a JSON response from HTTP GET. It works fine but I struggle decoding the following structure

"example": [
    {
      "param1": 4.88,
      "param2": 60,
      "param3": [
        {
          "param3_1": 501,
          "param3_2": "Rain",
        }
      ],
    },

I manage to extract param1 and param2 successfully with following code:

            JSONObject jo = (JSONObject) new JSONParser().parse(jsonString);
            JSONArray ja;
            Iterator<Map.Entry> itMap;
            Iterator itArray;

            ja = (JSONArray) jo.get("example");
            if (ja != null) {
                itArray = ja.iterator();
                while (itArray.hasNext()) {
                    ExampleClass e = new ExampleClass();
                    itMap = ((Map) itArray.next()).entrySet().iterator();
                    while (itMap.hasNext()) {
                        Map.Entry pair = itMap.next();
                        switch (pair.getKey().toString()) {
                            case "param1":
                                e.param1 = (double)pair.getValue();
                                break;
                            case "param2":
                                e.param2 = (long)pair.getValue();
                                break;
                            case "param3":
                                .....
                                break;
                            default:
                                break;
           }}}}

Does anyone know how to set up the iterator to get the param3 values?

Is there any significant difference or why should I use it instead of json.simple? — Mitch, Apr 19 '20 at 13:49
Pojo makes your life more and more easier and code cleaner and less complex. Please look into pojo with gson. — Karthik, Apr 19 '20 at 13:57
@Mitch your question sounds like why should I use collections instead of implementing my own LinkedList or Hashmap. Ofcourse you can implement LinkedList or Hashmap, but we use collection API to make our job simple. The same goes with GSON. — Trishul Singh Choudhary, Apr 19 '20 at 15:20

score 1 · Accepted Answer · answered Apr 19 '20 at 13:55

This is far more easier if you use a library like GSON. However, if you wish to continue as it is, following code would extract the content within param3. This is not a recommended way as the code would have to change if the attributes within the node gets changed.

Therefore, please try to use a JSON Parser next time

                        case "param3":
                        JSONArray jsonArray = ( JSONArray ) pair.getValue();
                        for( Object object : jsonArray )
                        {
                            JSONObject jsonObject = ( JSONObject ) object;
                            jsonObject.keySet().forEach( o ->
                            {
                                if( "param3_1".equalsIgnoreCase( o.toString() ) )
                                {
                                    // extract your value here
                                    long next = ( long ) jsonObject.get( o );
                                    System.out.println( next );
                                }
                                else if( "param3_2".equalsIgnoreCase( o.toString() ) )
                                {
                                    // extract your value here
                                    String next = String.valueOf( jsonObject.get( o ) );
                                    System.out.println( next );
                                }
                            } );
                        }
                        break;

Follow up this link if you wish to add GSON to this. This is a pretty easy and straight forward tutorial

Java Parse Json Array in another Json Array json.simple

1 Answers1