How to exclude a field from JSON using @Expose annotation in Java?

The Gson @Expose annotation can be used to mark a field to be exposed or not (included or not) for serialized or deserialized. The @Expose annotation can take two parameters and each parameter is a boolean which can take either the value true or false. In order to get GSON to react to the @Expose annotations we must create a Gson instance using the GsonBuilder class and need to call the excludeFieldsWithoutExposeAnnotation() method, it configures Gson to exclude all fields from consideration for serialization or deserialization that do not have the Expose annotation.

Syntax

public GsonBuilder excludeFieldsWithoutExposeAnnotation()

Example

import com.google.gson.*;
import com.google.gson.annotations.*;
public class JsonExcludeAnnotationTest {
   public static void main(String args[]) {
      Employee emp = new Employee("Raja", 28, 40000.00);
      Gson gson = new GsonBuilder().setPrettyPrinting().create();
      String jsonStr = gson.toJson(emp);
      System.out.println(jsonStr);
      gson = new GsonBuilder().setPrettyPrinting().excludeFieldsWithoutExposeAnnotation().create();
      jsonStr = gson.toJson(emp);
      System.out.println(jsonStr);
   }
}
// Employee class
class Employee {
   @Expose(serialize = true, deserialize = true)
   public String name;
   @Expose(serialize = true, deserialize = true)
   public int age;
   @Expose(serialize = false, deserialize = false)
   public double salary;
   public Employee(String name, int age, double salary) {
      this.name = name;
      this.age = age;
      this.salary = salary;
   }
}

Output

{
 "name": "Raja",
 "age": 28,
 "salary": 40000.0
}
{
 "name": "Raja",
 "age": 28
}