Convert JSON to comma-separated key=value pairs — Java

Sometimes you need to convert a JSON object into a compact, human-readable format — for logging, debugging, or passing metadata as a flat string. Here’s how to recursively flatten a nested JSON into comma-separated key=value pairs.

The Problem

Given this JSON:

{
  "app": {
    "versionCode": 15,
    "versionName": "1.4.6",
    "name": "latitude"
  },
  "os": {
    "name": "android",
    "version": "11"
  }
}

Convert it to:

app=(versionCode=15,versionName=1.4.6,name=latitude),os=(name=android,version=11)

Nested objects are wrapped in parentheses. Flat values are printed directly.

Solution

import org.json.JSONException;
import org.json.JSONObject;

import java.util.Iterator;

public class JsonToCommaSeparated {

    public static String getCommaSeparated(JSONObject object) throws JSONException {
        StringBuilder builder = new StringBuilder();
        if (object != null) {
            Iterator<String> iterator = object.keys();
            while (iterator.hasNext()) {
                String key = iterator.next();
                builder.append(key).append(‘=’);
                if (object.get(key) instanceof JSONObject) {
                    builder.append(‘(‘)
                            .append(getCommaSeparated((JSONObject) object.get(key)))
                            .append(‘)’);
                } else {
                    builder.append(object.get(key));
                }
                if (iterator.hasNext()) {
                    builder.append(‘,’);
                }
            }
        }
        return builder.toString();
    }

    public static void main(String[] args) throws JSONException {
        String json = """
                {
                  "app": {
                    "versionCode": 15,
                    "versionName": "1.4.6",
                    "name": "latitude"
                  },
                  "os": {
                    "name": "android",
                    "version": "11"
                  }
                }
                """;

        JSONObject object = new JSONObject(json);
        System.out.println(getCommaSeparated(object));

        // Flat JSON
        String flat = """
                {"city": "Bangalore", "country": "India"}
                """;
        System.out.println(getCommaSeparated(new JSONObject(flat)));

        // Empty JSON
        System.out.println(getCommaSeparated(new JSONObject("{}")));
    }
}

Output

app=(versionCode=15,versionName=1.4.6,name=latitude),os=(name=android,version=11)
city=Bangalore,country=India

How it works

1. Iterate through all keys in the JSON object
2. For each key, check if the value is another JSONObject
   • If yes, recurse and wrap the result in parentheses
   • If no, append the value directly
3. Add a comma between entries

The recursion handles any depth of nesting.