Exclude fields from Serialization with GSON API

GSON is a Java serialization/deserialization library to convert Java Objects into JSON and back.

In this post, we are going to see how we can exclude some fields from serialization with the GSON API.

Refer the below model class.

Employee.java

import org.apache.commons.lang3.builder.ToStringBuilder;

public class Employee {

    private String firstName;
    private String lastName;
    private int salary;

    public String getFirstName() {
        return firstName;
    }

    public void setFirstName(String firstName) {
        this.firstName = firstName;
    }

    public String getLastName() {
        return lastName;
    }

    public void setLastName(String lastName) {
        this.lastName = lastName;
    }

    public int getSalary() {
        return salary;
    }

    public void setSalary(int salary) {
        this.salary = salary;
    }

    @Override
    public String toString() {
        return ToStringBuilder.reflectionToString(this);
    }
}

The above Employee class has three fields such as first name, last name and salary. Consider that we want to exclude the salary field while serializing the employee object.

To do so, then we have to create a class which implements the ExclusionStrategy interface and provide our logic over there.

SalaryExclusionStrategy.java

import com.google.gson.ExclusionStrategy;
import com.google.gson.FieldAttributes;

public class SalaryExclusionStrategy implements ExclusionStrategy {

    @Override
    public boolean shouldSkipField(FieldAttributes f) {
        return "salary".equalsIgnoreCase(f.getName());
    }

    @Override
    public boolean shouldSkipClass(Class clazz) {
        return false;
    }
}

We need to instruct the GSON parser to ignore the salary field. So while creating the GSON object, we have to pass an instance of SalaryExclusionStrategy which contains the logic to ignore the salary field to the addSerializationExclusionStrategy method.

Refer the below code to know how we can do that.

import com.google.gson.FieldNamingPolicy;
import com.google.gson.Gson;
import com.google.gson.GsonBuilder;

public class GsonMain {

    private static final Gson GSON = new GsonBuilder()
            .setFieldNamingStrategy(FieldNamingPolicy.IDENTITY)
            .setPrettyPrinting()
            .addSerializationExclusionStrategy(new SalaryExclusionStrategy())
            .create();

    public static void main(String[] args) {
        Employee employee = new Employee();
        employee.setFirstName("Bala");
        employee.setLastName("Samy");
        System.out.println(GSON.toJson(employee));
    }
}

Refer below the output.

{
  "firstName": "Bala",
  "lastName": "Samy"
}

• GSON
• Java
• JSON