How to Convert JSON Strings to HashMaps in Java Using the org.json Library?

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;
}

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