In Java How to Convert Map / HashMap to JSONObject? [4 Different Ways]

Converting Objects from one form to another is a common request. There are 4 different ways to convert Java Map/HashMap to JSONObject.

We will go over details on how to convert HashMap to JSONObject in this tutorial.

Let’s get started:

Create class CrunchifyMapToJsonObject.java.

Method-1

Firstly we use Google GSON dependency to convert HashMap to JSONObject. You need below Maven dependency in your project.

<dependency>
	<groupId>com.google.code.gson</groupId>
	<artifactId>gson</artifactId>
	<version>2.8.0</version>
</dependency>

Method-2

Next we will use org.json dependency using new JSONObject().

<dependency>
	<groupId>org.json</groupId>
	<artifactId>json</artifactId>
	<version>20180130</version>
</dependency>

Method-3

Using jackson-core dependency with ObjectMapper().writeValueAsString() operation.

<dependency>
	<groupId>com.fasterxml.jackson.core</groupId>
	<artifactId>jackson-core</artifactId>
	<version>2.9.5</version>
	<scope>compile</scope>
</dependency>
<dependency>
	<groupId>com.fasterxml.jackson.core</groupId>
	<artifactId>jackson-databind</artifactId>
	<version>2.9.5</version>
	<scope>compile</scope>
</dependency>

Method-4

Using json-simple dependency with JSONValue.toJSONString() library.

<dependency>
	<groupId>com.googlecode.json-simple</groupId>
	<artifactId>json-simple</artifactId>
	<version>1.1.1</version>
</dependency>

Make sure to add all above maven dependencies to your Java J2EE project. If you don’t have maven project then follow these steps.

Here is a complete example:

package crunchify.com.tutorial;

import java.util.HashMap;
import java.util.Map;

import org.json.JSONObject;
import org.json.simple.JSONValue;

import com.fasterxml.jackson.core.JsonProcessingException;
import com.fasterxml.jackson.databind.ObjectMapper;
import com.google.gson.Gson;
import com.google.gson.GsonBuilder;

/**
 * @author Crunchify.com 
 * Program: 4 Best ways to convert Java Map to JSONObject. 
 * Version: 1.0.0
 * 
 */

public class CrunchifyMapToJsonObject {
	public static void main(String a[]) {

		Map<String, String> crunchifyMap = new HashMap<String, String>();
		crunchifyMap.put("Google", "San Jose");
		crunchifyMap.put("Facebook", "Mountain View");
		crunchifyMap.put("Crunchify", "NYC");
		crunchifyMap.put("Twitter", "SFO");
		crunchifyMap.put("Microsoft", "Seattle");
		log("Raw Map ===> " + crunchifyMap);

		// Use this builder to construct a Gson instance when you need to set configuration options other than the default.
		GsonBuilder gsonMapBuilder = new GsonBuilder();

		Gson gsonObject = gsonMapBuilder.create();

		String JSONObject = gsonObject.toJson(crunchifyMap);
		log("\nMethod-1: Using Google GSON ==> " + JSONObject);

		Gson prettyGson = new GsonBuilder().setPrettyPrinting().create();
		String prettyJson = prettyGson.toJson(crunchifyMap);

		log("\nPretty JSONObject ==> " + prettyJson);

		// Construct a JSONObject from a Map.
		JSONObject crunchifyObject = new JSONObject(crunchifyMap);
		log("\nMethod-2: Using new JSONObject() ==> " + crunchifyObject);

		try {
			// Default constructor, which will construct the default JsonFactory as necessary, use SerializerProvider as its 
			// SerializerProvider, and BeanSerializerFactory as its SerializerFactory.
			String objectMapper = new ObjectMapper().writeValueAsString(crunchifyMap);
			log("\nMethod-3: Using ObjectMapper().writeValueAsString() ==> " + objectMapper);
		} catch (JsonProcessingException e) {
			e.printStackTrace();
		}
		
		// Convert an object to JSON text. If this object is a Map or a List, and it's also a JSONAware, JSONAware will be considered firstly.
		String jsonValue = JSONValue.toJSONString(crunchifyMap);
		log("\nMethod-4: Using JSONValue.toJSONString() ==> " + jsonValue);

	}

	private static void log(Object print) {
		System.out.println(print);

	}
}

Just run above Program as Java Application and you should see below output.

Raw Map ===> {Google=San Jose, Twitter=SFO, Microsoft=Seattle, Facebook=Mountain View, Crunchify=NYC}

Method-1: Using Google GSON ==> {"Google":"San Jose","Twitter":"SFO","Microsoft":"Seattle","Facebook":"Mountain View","Crunchify":"NYC"}

Pretty JSONObject ==> {
  "Google": "San Jose",
  "Twitter": "SFO",
  "Microsoft": "Seattle",
  "Facebook": "Mountain View",
  "Crunchify": "NYC"
}

Method-2: Using new JSONObject() ==> {"Google":"San Jose","Twitter":"SFO","Microsoft":"Seattle","Facebook":"Mountain View","Crunchify":"NYC"}

Method-3: Using ObjectMapper().writeValueAsString() ==> {"Google":"San Jose","Twitter":"SFO","Microsoft":"Seattle","Facebook":"Mountain View","Crunchify":"NYC"}

Method-4: Using JSONValue.toJSONString() ==> {"Google":"San Jose","Twitter":"SFO","Microsoft":"Seattle","Facebook":"Mountain View","Crunchify":"NYC"}

If you know any other way to convert Java Map to JSONObject then please let us and all readers know by comment below.

Happy coding.