Transient keyword

Serialization is the process of converting object state into sequence of bytes. de-Serialization is a process to bring back the object’s state from bytes. if you don't want to serialize particular field, then make that field as transient.

import java.io.*;

public class Employee implements Serializable{
    int id;
    String firstName;
    transient String lastName;
    
    Employee(int id, String firstName, String lastName){
        this.id = id;
        this.firstName = firstName;
        this.lastName = lastName;
    }
    
    public static void main(String args[]) throws Exception{
        
        /* Serialize object */
        FileOutputStream fos = new FileOutputStream("ser.out");
        ObjectOutputStream out = new ObjectOutputStream(fos);
        Employee emp = new Employee(1, "Krishna", "Arjun");
        out.writeObject(emp);
        
        /* Deserialize object */
        FileInputStream fis = new FileInputStream("ser.out");
        ObjectInputStream in = new ObjectInputStream(fis);
        Employee emp1 = (Employee)in.readObject();
        
        System.out.println(emp1.id + " " + emp1.firstName +" " +emp1.lastName);
    }
}

Output

1 Krishna null

In the above program,

int id;

String firstName;

transient String lastName;

lastName is declared using the transient keyword, so it is not eligible for serialization. So when we print the Employee 'emp1', it prints null for lastName.

Related links
NotSerializableException
serialVersionUID
Externalization
Serialization Vs Externalization

                                                             Home