Converting JSON Strings to HashMaps in Java Using the org.json Library

When working with JSON data in Java, a common task is to convert JSON strings into HashMaps to facilitate data manipulation and storage. This article provides a detailed explanation on how to achieve this conversion using the org.json library.

JSON Structure

Consider the following JSON string:

{
"name" : "abc",
"email id" : ["[email protected]", "[email protected]", "[email protected]"]
}

The goal is to convert this JSON string into a HashMap with keys matching the property names and values corresponding to their respective values.

HashMap Initialization

First, initialize a HashMap to store the converted data:

Map<String, Object> retMap = new HashMap<String, Object>();

Recursive Conversion

The conversion process involves recursively traversing the JSON object and converting nested structures as well. The following code snippet outlines the recursive conversion method:

public static Map jsonToMap(JSONObject json) throws JSONException {
    Map<String, Object> retMap = new HashMap<String, Object>();

    if(json != JSONObject.NULL) {
        retMap = toMap(json);
    }
    return retMap;
}

public static Map toMap(JSONObject object) throws JSONException {
    Map map = new HashMap();

    Iterator keysItr = object.keys();
    while(keysItr.hasNext()) {
        String key = keysItr.next();
        Object value = object.get(key);

        if(value instanceof JSONArray) {
            value = toList((JSONArray) value);
        }

        else if(value instanceof JSONObject) {
            value = toMap((JSONObject) value);
        }
        map.put(key, value);
    }
    return map;
}

public static List