JSON String to Java Object using JSON-B


In Spring boot, we see how to convert json string to java object, we see about JSON-BINDING (jsonb), which is the standard for working between the java object and the json string. Json binding (Json-b) has recently been introduced to java as part of the JSR 367 specification. JSON binding api specifies the specifications for converting java object to json format and converting json string to java objects in spring boot.

It is necessary to convert a json string to java object in the spring boot application. Using a json string, a java object can be retrieved from a persistence layer like a database. The json string is a text that can be quickly transmitted across the network. In this post, we’ll see how to convert a json string to a java bean object.

The javax.json.bind dependency on the spring boot attaches the dependent jars to the spring boot project. Here we see the step-by-step process for building a spring boot application that converts a json string to a java object.



Step 1 – Create pom.xml with dependency

The first step is to build a spring boot application. The spring boot framework includes two simple “spring-boot-starter” and “spring-boot-starter-test” dependencies. To add json binding jars to the project, add “javax.json.bind-api” dependency to the pom.xml file. This is a specification api jar that enforces all json binding specifications.

Add the json binding jars to the spring boot program. The default json binding is org.eclipse.yasson. Add “org.eclipse.yasson” and “org.glassfish.javax.json” to the pom.xml file.

The pom.xml file below includes all the dependency for json binding.

pom.xml

<?xml version="1.0" encoding="UTF-8"?>
<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>
	<parent>
		<groupId>org.springframework.boot</groupId>
		<artifactId>spring-boot-starter-parent</artifactId>
		<version>2.2.5.RELEASE</version>
		<relativePath /> <!-- lookup parent from repository -->
	</parent>
	<groupId>com.yawintutor</groupId>
	<artifactId>Spring-Application</artifactId>
	<version>0.0.1-SNAPSHOT</version>
	<name>SpringBootJsonbSimple</name>
	<description>Spring Boot Project</description>

	<properties>
		<java.version>1.8</java.version>
	</properties>

	<dependencies>
		<dependency>
			<groupId>org.springframework.boot</groupId>
			<artifactId>spring-boot-starter</artifactId>
		</dependency>

		<dependency>
			<groupId>org.springframework.boot</groupId>
			<artifactId>spring-boot-starter-test</artifactId>
			<scope>test</scope>
		</dependency>

		<dependency>
			<groupId>javax.json.bind</groupId>
			<artifactId>javax.json.bind-api</artifactId>
		</dependency>

		<dependency>
			<groupId>org.eclipse</groupId>
			<artifactId>yasson</artifactId>
			<version>1.0.6</version>
		</dependency>

		<dependency>
			<groupId>org.glassfish</groupId>
			<artifactId>javax.json</artifactId>
			<version>1.1.4</version>
			<scope>provided</scope>
		</dependency>

	</dependencies>

	<build>
		<plugins>
			<plugin>
				<groupId>org.springframework.boot</groupId>
				<artifactId>spring-boot-maven-plugin</artifactId>
			</plugin>
		</plugins>
	</build>

</project>


Step 2 – Create Java Bean Class

Build a java bean object that will be transformed to a json object in the spring boot framework. The Java Bean object will contain all private variables and public getter and setter methods. The java bean object must have a default constructor.

The example below shows a sample of the java bean model.

Student.java

package com.yawintutor;

public class Student {

	private int id;

	private String name;

	public int getId() {
		return id;
	}

	public void setId(int id) {
		this.id = id;
	}

	public String getName() {
		return name;
	}

	public void setName(String name) {
		this.name = name;
	}

}


Step 3 – JSON Binding API code to convert Java Bean Object

The json binding api supports to create a java bean object by taking input as a json string. The example below demonstrates how to build a java bean object and how to convert a json string to java bean object.

SpringBootJsonbSimpleApplication.java

package com.yawintutor;

import javax.json.bind.Jsonb;
import javax.json.bind.JsonbBuilder;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;

@SpringBootApplication
public class SpringBootJsonbSimpleApplication {

	public static void main(String[] args) {
		SpringApplication.run(SpringBootJsonbSimpleApplication.class, args);

		JSONToJavaObject();
	}

	public static void JSONToJavaObject() {
		String jsonString = "{\"id\":100,\"name\":\"Yawin\"}";

		Jsonb jsonb = JsonbBuilder.create();
		Student st = jsonb.fromJson(jsonString, Student.class);
		System.out.println(st.getId() + " " + st.getName());
	}

}

Output


  .   ____          _            __ _ _
 /\\ / ___'_ __ _ _(_)_ __  __ _ \ \ \ \
( ( )\___ | '_ | '_| | '_ \/ _` | \ \ \ \
 \\/  ___)| |_)| | | | | || (_| |  ) ) ) )
  '  |____| .__|_| |_|_| |_\__, | / / / /
 =========|_|==============|___/=/_/_/_/
 :: Spring Boot ::        (v2.2.5.RELEASE)

2020-03-14 18:39:01.234  INFO 10439 --- [           main] c.y.SpringBootJsonbSimpleApplication     : Starting SpringBootJsonbSimpleApplication on banl1691b9157 with PID 10439 (/Users/yawin/STS/workspace/SpringBootJsonbSimple/target/classes started by Yawin in /Users/yawin/STS/workspace/SpringBootJsonbSimple)
2020-03-14 18:39:01.236  INFO 10439 --- [           main] c.y.SpringBootJsonbSimpleApplication     : No active profile set, falling back to default profiles: default
2020-03-14 18:39:01.654  INFO 10439 --- [           main] c.y.SpringBootJsonbSimpleApplication     : Started SpringBootJsonbSimpleApplication in 0.66 seconds (JVM running for 3.323)
100 Yawin



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