Convert Json String to Java Object Using GSON

Last Updated : 24 Jan, 2022

Pre-requisite: Convert Java Object to Json String Using GSON
JSON Stand for JavaScript Object Notation. It's a standard text-based format which shows structured data based on JavaScript object syntax. It is commonly used for transmitting data in web applications. JSON is highly recommended to transmit data between a server and web application.
To convert a Java object into JSON, the following methods can be used:

GSON: It is an open-source Java library which is used to serialize and deserialize Java objects to JSON.
Jackson API

In this article, a predefined JSON String is converted into Java Object using GSON.
Examples:

Input:
{
"organisation_name" : "GeeksforGeeks",
"description" : "A computer Science portal for Geeks",
"Employee" : "2000"
}
Output:
Organisation [organisation_name=GeeksforGeeks, description=A computer Science portal for Geeks, Employees=0]
Input:
{
"Student_name" : "XYZ",
"Organisation_name" : "GeeksForGeeks"
"Roll_No" : "1"
}
Output:
Student [Student_name=XYZ, Organisation_name=GeeksForGeeks, Roll_no=1]

The steps to do this are as follows:

Add jar files of Jackson (in case of Maven project add Gson dependencies in the pom.xml file)

html

 <dependency>
        <groupId>com.google.code.gson</groupId>
        <artifactId>gson</artifactId>
        <version>2.6.2</version>
    </dependency>

Below is the screenshot showing this step:-

Create a POJO (Plain Old Java Object) to be converted into JSON

Java

package GeeksforGeeks.Geeks;
public class Organisation {
    private String organisation_name;
    private String description;
    private int Employees;

    // Calling getters and setters
    public String getOrganisation_name()
    {
        return organisation_name;
    }
    public void setOrganisation_name(String organisation_name)
    {
        this.organisation_name = organisation_name;
    }
    public String getDescription()
    {
        return description;
    }
    public void setDescription(String description)
    {
        this.description = description;
    }
    public int getEmployees()
    {
        return Employees;
    }
    public void setEmployees(int employees)
    {
        Employees = employees;
    }

    // Creating toString
    @Override
    public String toString()
    {
        return "Organisation [organisation_name="
            + organisation_name
            + ", description="
            + description
            + ", Employees="
            + Employees + "]";
    }
}

Below is the screenshot showing this step:-

Create a String Variable for Storing Json String:
Note: This Json string should not be a simple Json String. Preprocess the JSON String and add slashes before passing it into GSON object.
Example of Preprocessing:

Initial JSON String:
{"organisation_name" : "GeeksforGeeks", "description" : "A computer Science portal for Geeks", "Employee" : "2000"}
Preprocessed JSON String:
{ \"organisation_name\" : \"GeeksforGeeks\", \"description\" : \"A computer Science portal for Geeks\", \"Employee\" : \"2000\" }

Create a Java class for converting the Json into Organisation object:

Java

package GeeksforGeeks.Geeks;

import com.google.gson.Gson;

public class JsonToObject {

    public static void main(String[] args)
    {
        // Creating object of Organisation
        Organisation org = new Organisation();

        // Converting json to object
        org = getOrganisationObject();

        // Displaying object
        System.out.println(org);
    }

    private static Organisation getOrganisationObject()
    {
        // Storing preprocessed json(Added slashes)
        String OrganisationJson
            = "{\"organisation_name\" 
            : \"GeeksforGeeks\",
            \"description\" 
            : \"A computer Science portal for Geeks\",
            \"Employee\" 
            : \"2000\"}";

        // Creating a Gson Object
        Gson gson = new Gson();

        // Converting json to object
        // first parameter should be preprocessed json
        // and second should be mapping class
        Organisation organisation
            = gson.fromJson(OrganisationJson,
                            Organisation.class);

        // return object
        return organisation;
    }
}