Preventing serialization of objects

In Java if the parent class is serializable then the child automatically is serializable. If for some reason you don't want the child to be serializable then you have to override the private methods readObject and writeObject to throw NotSerializableException. These are the same private methods which were used to customize serialization in my earlier post.

Example code on how to prevent serialization:

import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.NotSerializableException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.io.Serializable;

//Serializable class
class Animal implements Serializable {

    private static final long serialVersionUID = 1L;
    private String name;
    
    public Animal(String name) {
        this.name = name;
    }
    
    public String getName() {
        return name;
    }
}

//Does not want to be serializable
class Cat extends Animal {

    private static final long serialVersionUID = 1L;
    private String breed;
    private static final String NOT_SERIALIZABLE = "Cat cannot be serialized";
    
    public Cat (String name, String breed) {
        super(name);
        this.breed = breed;
    }
    
    public String getBreed() {
        return breed;
    }
    
    //To prevent serialization, override this method to throw exception
    private void readObject(ObjectInputStream ois) throws IOException, ClassNotFoundException {
        throw new NotSerializableException(NOT_SERIALIZABLE);
    }
        
    //To prevent serialization, override this method to throw exception
    private void writeObject(ObjectOutputStream oos) throws IOException {
        throw new NotSerializableException(NOT_SERIALIZABLE);
    }
}

//Test it
public class MyNonSerializableTest {

    public static void main(String[] args) throws FileNotFoundException, IOException {
        Animal a = new Animal("Cow");
        System.out.println("Serializing animal object");
        ObjectOutputStream out = new ObjectOutputStream(new FileOutputStream("animal.ser"));
        out.writeObject(a);
        Cat c = new Cat("bo", "Taby cat");
        System.out.println("Serializing cat object");
        ObjectOutputStream ous = new ObjectOutputStream(new FileOutputStream("cat.ser"));
        ous.writeObject(c);
    }
}

The output:
Serializing animal object
Serializing cat object
Exception in thread "main" java.io.NotSerializableException: Cat cannot be serialized
....blah blah blah.....