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.

The post In Java How to Convert Map / HashMap to JSONObject? [4 Different Ways] appeared first on Crunchify.

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