GSON – Serialize and Deserialize JSON

Learn to use Google GSON library to serialize Java Objects into their JSON representation and to deserialize a JSON string to an equivalent Java object. GSON provides simple toJson() and fromJson() methods to convert Java objects to JSON and vice-versa.

Use GsonBuilder to create Gson object with custom configurations such as pretty printing.

//Gson gson = new Gson();
Gson gson = new GsonBuilder().setPrettyPrinting().create();
		
Employee emp = new Employee(1001, "Lokesh", "Gupta", "howtodoinjava@gmail.com");

String jsonString = gson.toJson(emp);

Employee empObject = gson.fromJson(jsonString, Employee.class);

1. Dependency

Maven dependency. Visit maven repository for latest version.

<dependency>
  <groupId>com.google.code.gson</groupId>
  <artifactId>gson</artifactId>
  <version>2.8.5</version>
</dependency>

Gradle dependency.

<dependency>
dependencies {
  implementation 'com.google.code.gson:gson:2.8.5'
}

2. Serialization – Write JSON using Gson

Serialization in the context of Gson means converting a Java object to its JSON representation. In order to do the serialization, we need a Gson object, which handles the conversion. Next, we need to call the function toJson() and pass the Employee object.

Employee emp = new Employee(1001, "Lokesh", "Gupta", "howtodoinjava@gmail.com");
		
Gson gson = new Gson();

String jsonString = gson.toJson(emp);

System.out.println(jsonString);

Program output.

{
   "id":1001,
   "firstName":"Lokesh",
   "lastName":"Gupta",
   "email":"howtodoinjava@gmail.com"
}

2. Deserialization – Read JSON using Gson

Deserialization in the context of Gson means converting a JSON string to equivalent Java object. In order to do the deserialization, we need a Gson object and call the function fromJson() and pass two parameters i.e. JSON string and expected java type after parsing is finished.

String jsonString = "{'id':1001, 'firstName':'Lokesh', 'lastName':'Gupta', 'email':'howtodoinjava@gmail.com'}";
		
Gson gson = new Gson();

Employee empObject = gson.fromJson(jsonString, Employee.class);

System.out.println(empObject);

Program output.

Employee [id=1001, firstName=Lokesh, lastName=Gupta, email=howtodoinjava@gmail.com]

Drop me your question related to Gson object and it’s toJson() and fromJson() methods.

Happy Learning !!

References:

GSON Github