How to iterate over a JSONObject?

Question

I use a JSON library called JSONObject (I don\'t mind switching if I need to).

I know how to iterate over JSONArrays, but when I parse JSO

Answer 1

The simpler approach is (just found on W3Schools):

let data = {.....}; // JSON Object
for(let d in data){
    console.log(d); // It gives you property name
    console.log(data[d]); // And this gives you its value
}

UPDATE

This approach works fine until you deal with the nested object so this approach will work.

const iterateJSON = (jsonObject, output = {}) => {
  for (let d in jsonObject) {
    if (typeof jsonObject[d] === "string") {
      output[d] = jsonObject[d];
    }
    if (typeof jsonObject[d] === "object") {
      output[d] = iterateJSON(jsonObject[d]);
    }
  }
  return output;
}

And use the method like this

let output = iterateJSON(your_json_object);

Answer 2

I made my small method to log JsonObject fields, and get some stings. See if it can be usefull.

object JsonParser {

val TAG = "JsonParser"
 /**
 * parse json object
 * @param objJson
 * @return  Map<String, String>
 * @throws JSONException
 */
@Throws(JSONException::class)
fun parseJson(objJson: Any?): Map<String, String> {
    val map = HashMap<String, String>()

    // If obj is a json array
    if (objJson is JSONArray) {
        for (i in 0 until objJson.length()) {
            parseJson(objJson[i])
        }
    } else if (objJson is JSONObject) {
        val it: Iterator<*> = objJson.keys()
        while (it.hasNext()) {
            val key = it.next().toString()
            // If you get an array
            when (val jobject = objJson[key]) {
                is JSONArray -> {
                    Log.e(TAG, " JSONArray: $jobject")
                    parseJson(jobject)
                }
                is JSONObject -> {
                    Log.e(TAG, " JSONObject: $jobject")
                    parseJson(jobject)
                }
                else -> {
                    Log.e(TAG, " adding to map: $key $jobject")
                    map[key] = jobject.toString()
                }
            }
        }
    }
    return map
}
}

Answer 3

I once had a json that had ids that needed to be incremented by one since they were 0-indexed and that was breaking Mysql auto-increment.

So for each object I wrote this code - might be helpful to someone:

public static void  incrementValue(JSONObject obj, List<String> keysToIncrementValue) {
        Set<String> keys = obj.keySet();
        for (String key : keys) {
            Object ob = obj.get(key);

            if (keysToIncrementValue.contains(key)) {
                obj.put(key, (Integer)obj.get(key) + 1);
            }

            if (ob instanceof JSONObject) {
                incrementValue((JSONObject) ob, keysToIncrementValue);
            }
            else if (ob instanceof JSONArray) {
                JSONArray arr = (JSONArray) ob;
                for (int i=0; i < arr.length(); i++) {
                    Object arrObj = arr.get(0);
                    if (arrObj instanceof JSONObject) {
                        incrementValue((JSONObject) arrObj, keysToIncrementValue);
                    }
                }
            }
        }
    }

usage:

JSONObject object = ....
incrementValue(object, Arrays.asList("id", "product_id", "category_id", "customer_id"));

this can be transformed to work for JSONArray as parent object too

Answer 4

org.json.JSONObject now has a keySet() method which returns a Set<String> and can easily be looped through with a for-each.

for(String key : jsonObject.keySet())

Answer 5

We used below set of code to iterate over JSONObject fields

Iterator iterator = jsonObject.entrySet().iterator();

while (iterator.hasNext())  {
        Entry<String, JsonElement> entry = (Entry<String, JsonElement>) iterator.next();
        processedJsonObject.add(entry.getKey(), entry.getValue());
}

Answer 6

I will avoid iterator as they can add/remove object during iteration, also for clean code use for loop. it will be simply clean & fewer lines.

Using Java 8 and Lamda [Update 4/2/2019]

import org.json.JSONObject;

public static void printJsonObject(JSONObject jsonObj) {
    jsonObj.keySet().forEach(keyStr ->
    {
        Object keyvalue = jsonObj.get(keyStr);
        System.out.println("key: "+ keyStr + " value: " + keyvalue);

        //for nested objects iteration if required
        //if (keyvalue instanceof JSONObject)
        //    printJsonObject((JSONObject)keyvalue);
    });
}

Using old way [Update 4/2/2019]

import org.json.JSONObject;

public static void printJsonObject(JSONObject jsonObj) {
    for (String keyStr : jsonObj.keySet()) {
        Object keyvalue = jsonObj.get(keyStr);

        //Print key and value
        System.out.println("key: "+ keyStr + " value: " + keyvalue);

        //for nested objects iteration if required
        //if (keyvalue instanceof JSONObject)
        //    printJsonObject((JSONObject)keyvalue);
    }
}

Original Answer

import org.json.simple.JSONObject;
public static void printJsonObject(JSONObject jsonObj) {
    for (Object key : jsonObj.keySet()) {
        //based on you key types
        String keyStr = (String)key;
        Object keyvalue = jsonObj.get(keyStr);

        //Print key and value
        System.out.println("key: "+ keyStr + " value: " + keyvalue);

        //for nested objects iteration if required
        if (keyvalue instanceof JSONObject)
            printJsonObject((JSONObject)keyvalue);
    }
}