[Jackson API Examples] - How to Convert Java Map Object to/from JSON String using Jackson?(Serialize and De-serialize)

#JavaInspires

Hi Guys,

Welcome to Java Inspires.

In this post, we will see how to serialize and de-serialize java Map (HashMap) object using Jackson api.

Here, we are using ObjectMapper class from Jackson library and writeValueAsString method to convert serialize and readValue method to deserialize.

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How to Convert Java Map Object to/from JSON String using Jackson?(Serialize and Deserialize)

MainApp.java

package com.javainspires;

import java.io.IOException;
import java.util.Date;
import java.util.HashMap;
import java.util.Map;

import com.fasterxml.jackson.databind.ObjectMapper;
import com.fasterxml.jackson.databind.SerializationFeature;

/**
 * 
 * @author #JavaInspires
 *
 */
public class MainApp {

	public static void main(String[] args) throws IOException {

		// create a Map object
		Map<String, Object> sampleMap = new HashMap<>();
		sampleMap.put("name","Elon Musk");
		sampleMap.put("age", 45);
		sampleMap.put("doj", new Date());
		sampleMap.put("role", "Developer");

		// create object mapper class object
		ObjectMapper mapper = new ObjectMapper();
		mapper.enable(SerializationFeature.INDENT_OUTPUT);
		// convert map object to json string using this mapper
		String jsonStr = mapper.writeValueAsString(sampleMap);

		System.out.println("\nJava Map Object To JSON\n");
		// print json string
		System.out.println(jsonStr);

		// now convert this json string to java map object
		// using object mapper

		Map<String, Object> map1 = mapper.readValue(jsonStr.getBytes(), Map.class);

		System.out.println("\nJSON String to Java Map Object\n");
		// print this list
		map1.entrySet().forEach(System.out::println);

	}
}

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Output:

Java Map Object To JSON

{
  "role" : "Developer",
  "name" : "Elon Musk",
  "age" : 45,
  "doj" : 1623251901457
}

JSON String to Java Map Object

role=Developer
name=Elon Musk
age=45
doj=1623251901457

pom.xml

<project xmlns="http://maven.apache.org/POM/4.0.0"
	xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
	xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd">
	<modelVersion>4.0.0</modelVersion>
	<groupId>com.javainspires</groupId>
	<artifactId>jackson-examples</artifactId>
	<version>0.0.1-SNAPSHOT</version>

	<dependencies>

		<!-- https://mvnrepository.com/artifact/com.fasterxml.jackson.core/jackson-databind -->
		<dependency>
			<groupId>com.fasterxml.jackson.core</groupId>
			<artifactId>jackson-databind</artifactId>
			<version>2.12.2</version>
		</dependency>

	</dependencies>
</project>

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