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>();</string></string>

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<string object> 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<string object> toMap(JSONObject object) throws JSONException {
    Map<string object> map = new HashMap<string object>();

    Iterator<string> 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<object> toList(JSONArray array) throws JSONException {
    List<object> list = new ArrayList<object>();
    for(int i = 0; i <p>This code recursively traverses the JSON object and handles nested structures, such as arrays and objects, ensuring that the final HashMap contains all the data in the JSON string.</p>
<p><strong>Using the Jackson Library</strong></p>
<p>Alternatively, you can utilize the Jackson library for converting JSON strings to HashMaps. This can be done with the following code:</p>
<pre class="brush:php;toolbar:false">import com.fasterxml.jackson.databind.ObjectMapper;

Map<string object> mapping = new ObjectMapper().readValue(jsonStr, HashMap.class);</string>

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