Java Buzz Forum - Java Tutorial : Java IO (Java Externalizable | Java externalization

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Java Tutorial : Java IO (Java Externalizable | Java externalization | Custom Serialization)

Employee.java

import java.io.Externalizable;
import java.io.IOException;
import java.io.ObjectInput;
import java.io.ObjectOutput;

public class Employee implements Externalizable
{
    private int id;
    private String name;
    private int age;

    public Employee()
    {

    }

    public int getId()
    {
        return id;
    }

    public void setId(int id)
    {
        this.id = id;
    }

    public String getName()
    {
        return name;
    }

    public void setName(String name)
    {
        this.name = name;
    }

    public int getAge()
    {
        return age;
    }

    public void setAge(int age)
    {
        this.age = age;
    }

    @Override
    public String toString()
    {
        return "Employee [id=" + id + ", name=" + name + 
                ", age=" + age + "]";
    }

    @Override
    public void readExternal(ObjectInput in) throws IOException,
            ClassNotFoundException
    {
        System.out.println("Inside readExternal");
        id = in.readInt();
        name = (String) in.readObject();
    }

    @Override
    public void writeExternal(ObjectOutput out) throws IOException
    {
        System.out.println("Inside writeExternal");
        out.writeInt(id);
        out.writeObject(name);
    }

}

ExternalizableWrite.java

import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.ObjectOutputStream;

public class ExternalizableWrite
{

    public static void main(String[] args) throws FileNotFoundException,
            IOException, ClassNotFoundException
    {
        ExternalizableWrite externalizableWrite = new ExternalizableWrite();
        externalizableWrite.writeEmployeeObject();
    }

    private void writeEmployeeObject() throws FileNotFoundException,
            IOException
    {
        FileOutputStream fileOutputStream = null;
        ObjectOutputStream objectOutputStream = null;
        //Serialize
        try
        {
            fileOutputStream = new FileOutputStream("employee.ser");
            objectOutputStream = new ObjectOutputStream(fileOutputStream);

            Employee employee = new Employee();
            employee.setId(101);
            employee.setName("Peter");
            employee.setAge(25);

            System.out.println(employee);

            /*
             * Write the specified object to the
             * ObjectOutputStream.
             */
            objectOutputStream.writeObject(employee);
            System.out
                    .println("Successfully written employee object to the file.\n");
        }
        finally
        {

            if (objectOutputStream != null)
            {
                /*
                 * Closing a ObjectOutputStream will also
                 * close the OutputStream instance to which
                 * the ObjectOutputStream is writing.
                 */
                objectOutputStream.close();
            }
        }

    }

}

Output

Employee [id=101, name=Peter, age=25]
Inside writeExternal
Successfully written employee object to the file.

employee.ser

ExternalizableRead.java

import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.ObjectInputStream;

public class ExternalizableRead
{

    public static void main(String[] args) throws FileNotFoundException,
            IOException, ClassNotFoundException
    {
        ExternalizableRead externalizableRead = new ExternalizableRead();
        externalizableRead.readEmployeeObject();
    }

    private void readEmployeeObject() throws IOException,
            FileNotFoundException, ClassNotFoundException
    {
        FileInputStream fileInputStream = null;
        ObjectInputStream objectInputStream = null;
        //Deserialize 
        try
        {
            fileInputStream = new FileInputStream("employee.ser");
            objectInputStream = new ObjectInputStream(fileInputStream);

            /*
             * Read an object from the ObjectInputStream.
             */
            Employee employee = (Employee) objectInputStream.readObject();
            System.out.println(employee);
            System.out
                    .println("Successfully read employee object from the file.\n");

            System.out.println("Id  = " + employee.getId());
            System.out.println("Name = " + employee.getName());
            System.out.println("Age = " + employee.getAge());

        }
        finally
        {

            if (objectInputStream != null)
            {
                /*
                 * Closing a ObjectInputStream will also
                 * close the InputStream instance from which
                 * the ObjectInputStream is reading.
                 */
                objectInputStream.close();
            }
        }

    }

}

Output

Inside readExternal
Employee [id=101, name=Peter, age=0]
Successfully read employee object from the file.

Id  = 101
Name = Peter
Age = 0

Click the below link to download the code:
https://sites.google.com/site/ramj2eev1/home/javabasics/JavaIODemo_Externalizable_App.zip?attredirects=0&d=1

Github Link:
https://github.com/ramram43210/Java/tree/master/BasicJava/JavaIODemo_Externalizable_App

Bitbucket Link:
https://bitbucket.org/ramram43210/java/src/9f822df4c81f286daa095d86846058f3a9c16303/BasicJava/JavaIODemo_Externalizable_App/?at=master

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