Serialization and Deserialization In Java

In advanced Java, serialization and deserialization are processes to save and restore the state of an object, making it possible to store objects in files or databases, or transfer them over a network. Here’s a breakdown of these concepts and their application

1️⃣ Serialization

Serialization is the process of converting an object into a stream of bytes. This byte stream can be saved to a file, sent over a network, or stored in a database. In Java, the Serializable interface is used to indicate that a class can be serialized.

✍ Steps to serialize an object:

▶️ Implement the Serializable interface.

▶️ Use ObjectOutputStream and FileOutputStream to write the object to a file or output stream.

▶️ Call the writeObject() method on ObjectOutputStream.

👉Code Example:

import java.io.FileOutputStream;
import java.io.ObjectOutputStream;
import java.io.Serializable;

class Employee implements Serializable {
    private static final long serialVersionUID = 1L;
    String name;
    int id;

    public Employee(String name, int id) {
        this.name = name;
        this.id = id;
    }
}

public class SerializeDemo {
    public static void main(String[] args) {
        Employee emp = new Employee("John Doe", 101);

        try (FileOutputStream fileOut = new FileOutputStream("employee.ser");
             ObjectOutputStream out = new ObjectOutputStream(fileOut)) {
            out.writeObject(emp);
            System.out.println("Serialized data is saved in employee.ser");
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

Here, employee.ser is a serialized file that stores the object’s byte stream.

2️⃣ Deserialization
Deserialization is the reverse process, where the byte stream is converted back into a copy of the original object. This enables you to recreate the object’s state after it’s been stored or transferred.

✍ Steps to deserialize an object:

▶️ Use ObjectInputStream and FileInputStream to read the object from the file or input stream.

▶️ Call the readObject() method on ObjectInputStrea

👉Code Example:

import java.io.FileInputStream;
import java.io.ObjectInputStream;

public class DeserializeDemo {
    public static void main(String[] args) {
        Employee emp = null;

        try (FileInputStream fileIn = new FileInputStream("employee.ser");
             ObjectInputStream in = new ObjectInputStream(fileIn)) {
            emp = (Employee) in.readObject();
            System.out.println("Deserialized Employee...");
            System.out.println("Name: " + emp.name);
            System.out.println("ID: " + emp.id);
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

This will retrieve the object’s original state, allowing access to its fields as they were before serialization.

3️⃣ Advanced Serialization Topics

▶️ Custom Serialization: Override writeObject() and readObject() for customized serialization.

▶️ Externalizable Interface: Provides full control over serialization, requiring the implementation of writeExternal() and readExternal() methods.

▶️ Transient Fields: Use the transient keyword to avoid serializing specific fields (e.g., sensitive data like passwords).

✍ Advantages of Serialization:

▶️ Allows saving the state of an object for future use.

▶️ Facilitates the transfer of complex data objects over networks.

📝 Briefly Explain Code Example

import java.io.*;

class Student implements Serializable {
    private  static   final long serialVersionUId = 1l;
    private String name ;
    private int  age;
    private String Address;

    public Student(String name,int age,String Address){
        this.name = name;
        this.age = age;
        this.Address = Address;
    }
    public void setName(String name){
        this.name = name;
    }
    public void setAge(int age){
        this.age = age;
    }
    public void setAddress(String Address){
        this.Address = Address;
    }

    public String getName(){
        return name;
    }
    public String getAddress(){
        return Address;
    }
    public int getAge(){
        return age;
    }


    public String toString(){
        return ("Student name is "+this.getName()+", age is "+this.getAge()+", and address is "+this.getAddress());
    }
}

public class  JAVA3_Serialization {
    // when you implement Serializable then you must be write a serialVersionUId because when it serialise and deserialize it uniquely identify in the network
    // when u update ur object or anything then you have to update the serialVersionUId increment .
    // private  static   final long serialVersionUId = 1l;

    // transient  int x ;
    // If you do not want a particular value to serialise and Deserialize.
    // the value x, when you don't serialise and Deserialize Then transient you used.

    public static void main(String[] args) {

        Student student = new Student("kanha",21,"angul odisha");

        String filename = "D:\\Advance JAVA\\CLS3 JAVA\\Test.txt"; // store the data in this location
        FileOutputStream fileOut = null; // write file
        ObjectOutputStream objOut = null; // create object
        //Serialization
        try {
            fileOut = new FileOutputStream(filename);
            objOut = new ObjectOutputStream(fileOut);
            objOut.writeObject(student);

            objOut.close();
            fileOut.close();

            System.out.println("Object has been serialise =\n"+student);
        } catch (IOException ex){
            System.out.println("error will occure");
        }

        //Deserialization
        FileInputStream fileIn = null;
        ObjectInputStream objIn = null;
        try {
            fileIn = new FileInputStream(filename);
            objIn = new ObjectInputStream(fileIn);
            Student object =(Student) objIn.readObject();
            System.out.println("object has been Deserialization =\n"+object);

            objIn.close();
            fileIn.close();

        } catch (IOException e) {
            throw new RuntimeException(e);
        } catch (ClassNotFoundException e) {
            throw new RuntimeException(e);
        }
    }
}

✍ Key Notes:

▶️ Only non-static and non-transient data members are serialized by default.

▶️ Serializable objects must ensure compatibility between versions if the class is modified after serialization.

For more insights, feel free to mention your GitHub for in-depth examples and code samples! Let me know if you'd like any specific adjustments.

GitHub - https://github.com/Prabhanjan-17p