Getting started with GSON

build.gradle

repositories {
    mavenCentral()
}

dependencies {
    compile 'com.google.code.gson:gson:2.2.4'
}

Example1-Output

toJson ---
Original Java object : ModelObject [name=myname, val=12, status=true, f=2.3]
Converted JSON string is : {"name":"myname","val":12,"status":true,"f":2.3}
fromJson----
Original JSON string is : {"name":"myname","val":12,"status":true,"f":2.3}
Converted Java object : ModelObject [name=myname, val=12, status=true, f=2.3]

Example1.java

package in.ajduke.ap012;

import com.google.gson.Gson;

/**
 * An example of Gson demo
 * 
 * @author ajduke
 * 
 */
public class GsonExample {
	public static void main(String[] args) {

		final Gson gson = new Gson();
		// original object instantiation
		ModelObject modelObject = new ModelObject("myname", 12, true, 2.3);
		System.out.println("toJson ---");
		System.out.println("Original Java object : " + modelObject);
		// converting an object to json object
		String json = gson.toJson(modelObject);
		System.out.println("Converted JSON string is : " + json);

		System.out.println("fromJson----");
		// getting object from json representation
		System.out.println("Original JSON string is : " + json);
		// converting json to object
		ModelObject modelObject1 = gson.fromJson(json, ModelObject.class);
		System.out.println("Converted Java object : " + modelObject1);
	}
}

Example2-Output

A generic object demo
json representation :{"value":12}
converted object representation: Model2 [value=12]

A object from collection framework

json representation :["ajduke","ajduchess"]
converted object representation: [ajduke, ajduchess]

Example2.java

package in.ajduke.ap012;

import java.lang.reflect.Type;
import java.util.ArrayList;
import java.util.List;

import com.google.gson.Gson;
import com.google.gson.reflect.TypeToken;

/**
 * An example of Gson demo
 * 
 * @author ajduke
 * 
 */
public class GsonExample {

  public static void main(String[] args) {
		Gson gson = new Gson();

		System.out.println("A generic object demo");
		// a generified object
		GenericModel<Integer> model = new GenericModel<>(12);

		// converting to json representation
		String json = gson.toJson(model);
		System.out.println("json representation :" + json);

		// converting back to object
		Type collectionType = new TypeToken<GenericModel<Integer>>() {
		}.getType();
		GenericModel<Integer> modelObj = gson.fromJson(json, collectionType);
		System.out.println("converted object representation: " + modelObj);

		System.out.println("\nA object from collection framework\n");
		// for collection framework objects
		List<String> listOfString = new ArrayList<>();
		listOfString.add("ajduke");
		listOfString.add("ajduchess");

		// conversion to json
		String jsonStr = gson.toJson(listOfString);
		System.out.println("json representation :" + jsonStr);

		Type collectionType2 = new TypeToken<List<String>>() {
		}.getType();
		List<String> listObj = gson.fromJson(jsonStr, collectionType2);
		System.out.println("converted object representation: " + listObj);

	}
}

Example3-Output

Original Java object : ModelObject [name=namesake, val=50, status=true, f=4.3]
Converted JSON string is : {"name":"namesake","status":true,"f":4.3}
Converted Java object : ModelObject [name=namesake, val=0, status=true, f=4.3]

Example3.java

package in.ajduke.ap012;

import com.google.gson.Gson;

/**
 * An example of Gson demo
 * 
 * @author ajduke
 * 
 */
public class GsonExample {

public static void main(String[] args) {
  	Gson gson = new Gson();
		// original object
		ModelObject modelObject = new ModelObject("namesake", 50, true, 4.3);
		System.out.print("Original Java object : ");
		System.out.println(modelObject);

		// converting to an json representation
		String json = gson.toJson(modelObject);
		System.out.print("Converted JSON string is : ");
		System.out.println(json);

		// getting back the object from json representation
		ModelObject modelObject3 = gson.fromJson(json, ModelObject.class);
		System.out.print("Converted Java object : ");
		System.out.println(modelObject3);
}
}

GenericModel.java

package in.ajduke.ap012;
/**
 * An generified model for demo of gson conversion 
 * @author ajduke
 */
public class GenericModel<T> {
  T value;

	public GenericModel(T value) {
		super();
		this.value = value;
	}

	@Override
	public String toString() {
		return "Model2 [value=" + value + "]";
	}

}

ModelObject.java

package in.ajduke.ap012;
/**
 * An model for demo of gson conversion 
 * 
 * @author ajduke
 * 
 */
public class ModelObject {
  String name;
	int val;
	boolean status;
	double f;

	public ModelObject(String name, int val, 
	boolean status, double f) {
		super();
		this.name = name;
		this.val = val;
		this.status = status;
		this.f = f;
	}

	@Override
	public String toString() {
		return "ModelObject [name=" + name + ",
		val=" + val + ", status="
		+ status + ", f=" + f + "]";
	}

}

ModelObject2.java

package in.ajduke.ap012;
/**
 * An model for demo of gson conversion 
 * 
 * @author ajduke
 * 
 */
public class ModelObject {
  String name;
  transient int val;
	boolean status;
	double f;
 
	public ModelObject(String name, int val, 
	boolean status, double f) {
		super();
		this.name = name;
		this.val = val;
		this.status = status;
		this.f = f;
	}
 
	@Override
	public String toString() {
		return "ModelObject [name=" + name + ",
		val=" + val + ", status="
		+ status + ", f=" + f + "]";
	}
 
}

pom.xml

<dependency>
    <groupId>com.google.code.gson</groupId>
    <artifactId>gson</artifactId>
    <version>2.2.4</version>
</dependency>

Thanks for the introduction