Java Serialization Lesion 02

Java Serialization Lesion 02

Object Serialization –

objects represents as a sequence of bytes.

This includes the object's data, informations about the objects type, and the types of data stored in th e object.

Serialized object can read once it deserialized and recreate the object in the memory.

This serialization and deserialization process is JVM independent.

( object can serialized in one platform and can deserialized on another platform )

ObjectInputStream class - for serializing an object

- public final void writeObject(Object x) throws IOException

ObjectOutputStream class - for deserializing an object

- public final Object readObject() throws IOException, ClassNotFoundException

Since by using serialization, Java object can write into a file for future access.

A class to be serialized successfully

1. The class must implement the java.io.Serializable interface.

2. All of the fields in the class must be serializable. If a field is not serializable, it must be marked transient.

Example of serialize and deserialize process -

i) Serializing an Object:

The ObjectOutputStream class is used to serialize an Object. Following program instantiates an Employee object and serializes it to a file.

When the program is done executing, a file named employee.ser is created.

Note: When serializing an object to a file, the standard convention in Java is to give the file a .ser extension.

ii) Deserializing an Object:

Use .ser to deserializes and create the Employee object

1. Employee class

package JavaSerialize;

import java.io.Serializable;

public class Employee implements Serializable {

/**

*

*/

private static final long serialVersionUID = 1L;

private String firstName;

private String lastName;

private int age;

private transient int SSN;

private String designation;

private String jobTitle;

private String project;

//TODo generate getters and setters

}

1. DemoSerializDeSerialize class

package JavaSerialize;

import java.io.FileInputStream;

import java.io.FileOutputStream;

import java.io.IOException;

import java.io.ObjectInputStream;

import java.io.ObjectOutputStream;

public class DemoSerializeDeSerialize {

private int EXECUTE = 1; // 0 - Serialize | 1 - Deserialize

/**

* @param args

*/

  public static void main(String[] args) {

    DemoSerializeDeSerialize demo = new DemoSerializeDeSerialize();

    demo.execute();

  }

  private void execute(){

    

    if(EXECUTE == 0){

      doSerialize();

    }else{

      doDeSerialize();

    }

  }

  private void doSerialize(){

    Employee employee = buildEmployee();

    try{

     FileOutputStream fileOut = new FileOutputStream("/home/sanjeeva/Desktop/employee.ser");

     ObjectOutputStream out = new ObjectOutputStream(fileOut);

     out.writeObject(employee);

     out.close();

     fileOut.close();

     System.out.printf("Serialized data is saved in /home/sanjeeva/Desktop/employee.ser");

    }catch(IOException ioe){

      ioe.printStackTrace();

    }

  }

  private void doDeSerialize(){

     Employee employee = null;

     try{

       FileInputStream fileIn = new FileInputStream("/home/sanjeeva/Desktop/employee.ser");

       ObjectInputStream in = new ObjectInputStream(fileIn);

       employee = (Employee) in.readObject();

       in.close();

       fileIn.close();

       }catch(IOException ioe){

          ioe.printStackTrace();

          return;

       }catch(ClassNotFoundException c){

          System.out.println("Employee class not found");

          c.printStackTrace();

          return;

       }

       System.out.println("Deserialized Employee...");

       System.out.println("First Name: " + employee.getFirstName());

       System.out.println("Last Name: " + employee.getLastName());

       System.out.println("SSN: " + employee.getSSN());

       System.out.println("Designation: " + employee.getDesignation());

       System.out.println("JobTitle: " + employee.getJobTitle());

       System.out.println("Project: " + employee.getProject());

  }

  private Employee buildEmployee(){

      Employee employee = new Employee();

      employee.setFirstName("Sanjeeva");

      employee.setFirstName("Pathirana");

      employee.setAge(30);

      employee.setDesignation("Senior Software Engineer");

      employee.setJobTitle("Team Lead");

      employee.setProject("ABC Project");

      employee.setSSN(100123);

      return employee;

  }

}

By changing the EXECUTE parameter can do the serialization and deserialization.

There is no out put for serialization and it creates the .ser file.

Serialized data is saved in /home/sanjeeva/Desktop/employee.ser

The deserialization process the out put as follows.

Deserialized Employee...

First Name: Sanjeeva

Last Name: Pathirana

SSN: 0

Designation: Senior Software Engineer

JobTitle: Team Lead

Project: ABC Project

Note : The value of the SSN field was 100123 when the object was serialized, but because the field is transient, this value was not sent to the output stream. The SSN field of the deserialized Employee object is 0.