How to parse JSON in Spring Boot using ObjectMapper

In this tutorial we will learn how to parse JSON using the ObjectMapper API in a Spring Boot application.

The Jackson com.fasterxml.jackson.databind.ObjectMapper class is a simple way to parse and create JSON. The Jackson ObjectMapper can parse JSON from a string, stream or file, and create a Java object or object graph representing the parsed JSON.

Let's see quick example:

package com.example.demojson;

import java.util.List;

import org.springframework.boot.CommandLineRunner;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.context.annotation.Bean;
import com.fasterxml.jackson.core.JsonParser.Feature;
import com.fasterxml.jackson.core.type.TypeReference;
import com.fasterxml.jackson.databind.ObjectMapper;

public class DemoApplication {

	public static void main(String[] args) {, args);
	CommandLineRunner runner() {
		return args -> {
			String json = " {\n" + 
					"    \"name\": \"Edmund lronside\",\n" + 
					"    \"city\": \"United Kingdom\",\n" + 
					"    \"house\": \"House of Wessex\",\n" + 
					"    \"years\": \"1016\"\n" + 
					"  }";
			ObjectMapper mapper = new ObjectMapper();
			King c = mapper.readValue(json, King.class);

In the above example, we are parsing a simple JSON String and converting it into a Java class:

package com.example.demojson;

public class King {
	String name;
	String city;
	String house;
	String years;
	public String getName() {
		return name;
	public void setName(String name) { = name;
	public String getCity() {
		return city;
	public void setCity(String city) { = city;
	public String getHouse() {
		return house;
	public void setHouse(String house) { = house;
	public String getYears() {
		return years;
	public void setYears(String years) {
		this.years = years;
	public King() {
		// TODO Auto-generated constructor stub
	public King(String name, String city, String house, String years) {
		super(); = name; = city; = house;
		this.years = years;
	public String toString() {
		return "King [name=" + name + ", city=" + city + ", house=" + house + ", years=" + years + "]";

In the following example, we are parsing a JSON external file and converting it into a List of Java objects:

TypeReference<List<King>> typeReference = new TypeReference<List<King>>(){};
List<King> list= mapper.readValue(new File("/tmp/sample.json"), typeReference);
for (King k: list)

Notice the TypeReference parameter passed to readValue(). This parameter tells Jackson to read a List of King objects.

You can also use the ObjectMapper API to produce JSON Strings into a File, as in the following example:

ObjectMapper objectMapper = new ObjectMapper();
King king = new King("Edward the Martyr","United Kingdom","House of Wessex","975-978");
objectMapper.writeValue(new File("target/king.json"), king);

Check fields which are null

It is possible to configure the Jackson ObjectMapper to fail if a JSON string contains a field with its value set to null:

objectMapper.configure(DeserializationFeature.FAIL_ON_NULL_FOR_PRIMITIVES, true);

In the above example, you will get an exception when trying to parse a null JSON field into a primitive Java field.

FREE WildFly Application Server - JBoss - Quarkus - Drools Tutorials
Cookie Policy

Cookie Policy This website uses cookies that are necessary to its functioning and required to achieve the purposes illustrated in the privacy policy. By accepting this OR scrolling this page OR continuing to browse, you agree to our privacy policy.

© 2020 Your Company. All Rights Reserved. Designed By JoomShaper

Please publish modules in offcanvas position.