SerializationExamples.java

package concept.examples.serialization;

import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.io.Serializable;

class Rectangle implements Serializable {
	public Rectangle(int length, int breadth) {
		this.length = length;
		this.breadth = breadth;
		area = length * breadth;
	}

	int length;
	int breadth;
	transient int area;

	private void writeObject(ObjectOutputStream os) throws IOException {
		// Do whatever java does usually when serialization is called
		os.defaultWriteObject();
	}

	private void readObject(ObjectInputStream is) throws IOException,
			ClassNotFoundException {
		// Do whatever java does usually when de-serialization is called
		is.defaultReadObject();
		// In addition, calculate area also
		area = this.length * this.breadth;
	}
}

public class SerializationExamples {

	public static void main(String[] args) throws IOException,
			ClassNotFoundException {
		// Serialization helps us to save and retrieve the state of an object.
		// Serialization => Convert object state to some internal object
		// representation.
		// De-Serialization => The reverse. Convert internal representation to
		// object.
		// Two important methods
		// ObjectOutputStream.writeObject() // serialize and write to file
		// ObjectInputStream.readObject() // read from file and deserialize

		// To serialize an object it should implement Serializable interface
		// class Rectangle implements Serializable

		// Serializing an object
		FileOutputStream fileStream = new FileOutputStream("Rectangle.ser");
		ObjectOutputStream objectStream = new ObjectOutputStream(fileStream);
		objectStream.writeObject(new Rectangle(5, 6));
		objectStream.close();

		// Deserializing an object
		FileInputStream fileInputStream = new FileInputStream("Rectangle.ser");
		ObjectInputStream objectInputStream = new ObjectInputStream(
				fileInputStream);
		Rectangle rectangle = (Rectangle) objectInputStream.readObject();
		objectInputStream.close();
		System.out.println(rectangle.length);// 5
		System.out.println(rectangle.breadth);// 6
		System.out.println(rectangle.area);// 30
	}
}