Serialization and Deserialization in Java | Code Factory

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Java Serialization allows us to convert Java Object to a Stream of bytes which we can send through a network or save in a file or even in a DB for future usage. Deserialization is the process of converting a stream of bytes back to Java Object which can be used in our program. We will be implementing java.io.Serializable interface to achieve serialization

The serializable interface in java is a marker interface (method with no body).

Employee.java

package com.codeFactory;
import java.io.Serializable;
/**
 * @author code.factory
 *
 */
public class Employee implements Serializable {
private int id;
 private String name;
public Employee(int id, String name) {
  this.id = id;
  this.name = name;
 }
public int getId() {
  return id;
 }
public String getName() {
  return name;
 }
@Override
 public String toString() {
  return "Employee : [id : " + id + ", name : " + name + "]";
 }
}

SerializableUtility.java

package com.codeFactory;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
/**
 * @author code.factory
 *
 */
public class SerializableUtility {
public void serialize(Object object, String filePath) {
  try {
   FileOutputStream fos = new FileOutputStream(filePath);
   ObjectOutputStream oos = new ObjectOutputStream(fos);
   oos.writeObject(object);
   oos.flush();
   oos.close();
  } catch (Exception e) {
   e.printStackTrace();
  }
 }
 
 public Object deserialize(String filePath) {
  Object object = null;
  try {
   FileInputStream fis = new FileInputStream(filePath);
   ObjectInputStream ois = new ObjectInputStream(fis);
   object = ois.readObject();
  } catch (Exception e) {
   e.printStackTrace();
  }
  return object;
 }
}

Main.java

package com.codeFactory;
/**
 * @author code.factory
 *
 */
public class Main {
final private static String filePath = "Test.txt";
 
 public static void main(String... args) {
  Employee emp = new Employee(1, "Code Factory");
  
  SerializableUtility su = new SerializableUtility();
  su.serialize(emp, filePath);
  
  Employee employee = (Employee) su.deserialize(filePath);
  System.out.println(employee);
 }
}

Output :

Employee : [id : 1, name : Code Factory]

Is sub class Serializable?

If the parent class is Serializable then all the sub class will be Serializable as well.

Person.java

package com.codeFactory;
/**
 * @author code.factory
 *
 */
public class Person extends Employee {
private String name;
public Person(String name) {
  super(2, name);
  this.name = name;
 }
public String getName() {
  return name;
 }
}

Main.java

package com.codeFactory;
/**
 * @author code.factory
 *
 */
public class Main {
final private static String filePath = "Test.txt";
 
 public static void main(String... args) {
  Employee emp = new Employee(1, "Code Factory");
  Person person = new Person("Person");
  
  SerializableUtility su = new SerializableUtility();
  su.serialize(person, filePath);
  
  Employee employee = (Employee) su.deserialize(filePath);
  System.out.println(employee);
 }
}

Output :

Employee : [id : 2, name : Person]

Other Class Reference in a Serializable class

If we have a non-serializable reference of a class inside a Serializable class, then serialization operation will not be performed.In such case, NonSerializableException will be thrown.

I have changed code of Employee.java and Person.java classes

Employee.java

package com.codeFactory;
import java.io.Serializable;
/**
 * @author code.factory
 *
 */
public class Employee implements Serializable {
private int id;
 private Person person;
public Employee(int id, Person person) {
  this.id = id;
  this.person = person;
 }
public int getId() {
  return id;
 }
public Person getPerson() {
  return person;
 }
@Override
 public String toString() {
  return "Employee : [id : " + id + ", person : " + person.getName() + "]";
 }
}

Person.java

package com.codeFactory;
/**
 * @author code.factory
 *
 */
public class Person {
private String name;
public Person(String name) {
  this.name = name;
 }
public String getName() {
  return name;
 }
}

Main.java

package com.codeFactory;
/**
 * @author code.factory
 *
 */
public class Main {
final private static String filePath = "Test.txt";
 
 public static void main(String... args) {
  Employee emp = new Employee(1, new Person("Code Factory"));
  
  SerializableUtility su = new SerializableUtility();
  su.serialize(emp, filePath);
  
  Employee employee = (Employee) su.deserialize(filePath);
  System.out.println(employee);
 }
}

Output :

java.io.NotSerializableException: com.codeFactory.Person
 at java.io.ObjectOutputStream.writeObject0(Unknown Source)
 at java.io.ObjectOutputStream.defaultWriteFields(Unknown Source)
 at java.io.ObjectOutputStream.writeSerialData(Unknown Source)
 at java.io.ObjectOutputStream.writeOrdinaryObject(Unknown Source)
 at java.io.ObjectOutputStream.writeObject0(Unknown Source)
 at java.io.ObjectOutputStream.writeObject(Unknown Source)
 at com.codeFactory.SerializableUtility.serialize(SerializableUtility.java:18)
 at com.codeFactory.Main.main(Main.java:15)