Impact of Inheritance on serialization example in java (Concrete class serializable)

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  • Given a base & concrete class in java.
  • Base class is not Serializable
  • Concrete class implements Serializable interface and extending its base class
  • Base class must have default or no arg constructor.
  • We have discussed
    • Impact of Inheritance on serialization in java, when base class is serializable.

Impact of serialization on inheritance in java

1.) What happens, when concrete class is serialized?

  • Date members of concrete class will get serialized
  • Date members of base class will not get serialized

2.) What happens, when concrete class is deserialized?

  • Data members of concrete class gets deserialized
  • Data members of base class get default value
Serialization subclass example
Fig 1: Employee implements Serializable

Code: Serialization when concrete class is serializable

1.) Person (Base) class (is not serializable)

  • Person class does not implements Serializable interface.
  • Data members of Person class will not be serialized.
package org.learn;
 
public class Person {
 
    public String firstName;
    public int age;
    public String contact;
    public Person(String firstName,int age, String contact) {
        this.firstName = firstName;
        this.age = age;
        this.contact = contact;
    }
    public Person() {
         
    }
    public String toString() {
        return "[" + firstName +
               " " + age + " " +contact +"]";
    }
}

2.) Employee (Concrete) class implements Serializable interface

  • Employee class implements Serializable marker interface
  • Employee class extends Person class.
  • When we will serialize the Employee object
    • Data member pertaining to employee object will gets serialized
    • Data members of person class will not get serialized.
  • When we deserialize the employee object
    • Employee data members will gets deserialized.
    • Person data members will get default values (will not get serialized).
package org.learn;
 
import java.io.Serializable;
 
public class Employee extends Person implements Serializable {
 
    private static final long serialVersionUID = 1L;
    public String department;
    public int employCode = 1010;
    public int salary;
    public Employee(String department,int salary, int employCode,
            String firstName,int age, String contact) {
        super(firstName,age, contact);
        this.department = department;
        this.salary = salary;
        this.employCode = employCode;      
    }
     
    public String toString() {
        return  super.toString() + "[" + department + " " + employCode +
               " " + salary + "]";
    }
}

3.) SerializeDeserialize class

  • SerializeDeserialize class contains main function.
  • SerializeDeserialize class will serialize and deserialize the Employee object.
package org.learn;
 
import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
 
public class SerializeDeserialize {
 
    public static void serialize() throws IOException {
        Employee employee = new Employee("IT", 25, 9999, "Mike", 34, "001894536");
        //Set static variable
        FileOutputStream output = new FileOutputStream(new File("savePerson.txt"));
        ObjectOutputStream outputStream = new ObjectOutputStream(output);
        outputStream.writeObject(employee);
        output.close();
        outputStream.close();
        System.out.println("Serialized the employee object : "+employee);
    }
    public static void deSerialize() throws IOException, ClassNotFoundException {
         
        FileInputStream inputStream = new FileInputStream(new File("savePerson.txt"));
        ObjectInputStream objectInputStream = new ObjectInputStream(inputStream);
        Employee employee = (Employee) objectInputStream.readObject();
        System.out.println("Deserialize the employee object :"+ employee);
                objectInputStream.close();
        inputStream.close();
    }
     
    public static void main(String[] args) throws IOException, ClassNotFoundException {
        serialize();
        deSerialize();
    }
}

Output: Serialization in java, drive class is serializable

Serialized the employee object : [Mike 34 001894536][IT 9999 25]
Deserialize the employee object :[null 0 null][IT 9999 25]

Download Code : Inheritance & serialization in java

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