JSONSimple Overwriting

Question

I am attempting to iterate through a hash map and create a json string from the values. Im using the JSONSimple library to do so. I have the structure I want, but the values are being overwritten. The structure I am ending up with is

{
   "new_id":{
      "coordinates_list":{
         "Coordinates: ":[
            "lat: 27.0",
            "lon: 28.0"
         ]
      },
      "t0vhf40cv86t":[
         "123"
      ]
   }
}

But there should be additional values in the JSON. Only the last row of the hash map is being included. Do I need to add another JSONObject that I write to?

JSONObject obj = new JSONObject(); // final json object written out

    double lat = 20.00; // test data
    double lon = 21.00; // test data
    for (Map.Entry<String, List<String>> entry : data.entrySet()){
        JSONObject childObj = new JSONObject();
        JSONObject coordObj = new JSONObject();

        JSONArray entities = new JSONArray();
        JSONArray coordinates = new JSONArray();

        String key = entry.getKey();
        List<String> values = data.get(key);
        for(String value : values){
            entities.add(value);
        }
        childObj.put(key,entities);

        // increments the test data 
        lat = lat +1;
        lon = lon + 1;

        coordinates.add("lat: " + lat);
        coordinates.add("lon: " + lon);

        coordObj.put("Coordinates: " ,coordinates);

        childObj.put("coordinate list ", coordObj);

        obj.put("new_id" , childObj);

    }

Why are you doing `List values = data.get(key)`, shouldn't it be `List values = entry.getValue()`? — Jonny Henly, Oct 10 '16 at 20:39

score 2 · Accepted Answer · answered Oct 10 '16 at 20:42

2

You are always using "new_id" as the key on the "obj.put" line. For the first map entry, you set the value for that key on the JSON object. For each subsequent entry, you are replacing the value for that key, not adding a new key. That is why only the last entry in the map is represented in the JSON.

I'm not sure exactly what you're trying to accomplish, but you likely either need to use a different key each time through the loop or use a JSONArray instead of a JSONObject so that you don't need keys at all.

answered Oct 10 '16 at 20:42

Todd Dunlap

141
6

1

Up-voted for being the right answer, but `put()`'s documentation might better explain the situation: "`put(String name, Object value)` - Maps `name` to `value`, clobbering any existing name/value mapping with the same name." – Jonny Henly Oct 10 '16 at 20:45
@JonnyHenly thanks, I didn't know that. What's the procedure if I want to create something that will always be the same? Say I want to add "Type" : "Feature" to every item. Is that not possible? – Rob Jarvis Oct 11 '16 at 18:34
If you don't want to add that field to your classes, then you probably want to do something like [this](http://stackoverflow.com/questions/14714328/jackson-how-to-add-custom-property-to-the-json-without-modifying-the-pojo). – Todd Dunlap Oct 11 '16 at 18:50

JSONSimple Overwriting

1 Answers1