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Java object serialization. This tutorial explains how to use Java serialization and de-serialization.

1. Java Serialization

Via Java Serialization you can stream your Java object to a sequence of byte and restore these objects from this stream of bytes. To make a Java object serializable you implement the java.io.Serializable interface. This is only a marker interface which tells the Java platform that the object is serializable.

Certain system-level classes such as Thread, OutputStream and its subclasses, and Socket are not serializable. If you serializable class contains such objects, it must mark then as "transient".

2. Example

Create a Java project called "de.vogella.java.serilization". Create the following Java object called Person.

package de.vogella.java.serilization;

import java.io.Serializable;

public class Person implements Serializable {
    private String firstName;
    private String lastName;
    // stupid example for transient
    transient private Thread myThread;

    public Person(String firstName, String lastName) {
        this.firstName = firstName;
        this.lastName = lastName;
        this.myThread = new Thread();
    }

    public String getFirstName() {
        return firstName;
    }

    public void setFirstName(String firstName) {
        this.firstName = firstName;
    }

    public String getLastName() {
        return lastName;
    }

    public void setLastName(String lastName) {
        this.lastName = lastName;
    }

    @Override
    public String toString() {
        return "Person [firstName=" + firstName + ", lastName=" + lastName
                + "]";
    }

}

The following code example show you how you can serializable and de-serializable this object.

package de.vogella.java.serilization;

import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;

public class Main {
    public static void main(String[] args) {
        String filename = "time.ser";
        Person p = new Person("Lars", "Vogel");

        // save the object to file
        FileOutputStream fos = null;
        ObjectOutputStream out = null;
        try {
            fos = new FileOutputStream(filename);
            out = new ObjectOutputStream(fos);
            out.writeObject(p);

            out.close();
        } catch (Exception ex) {
            ex.printStackTrace();
        }
        // read the object from file
        // save the object to file
        FileInputStream fis = null;
        ObjectInputStream in = null;
        try {
            fis = new FileInputStream(filename);
            in = new ObjectInputStream(fis);
            p = (Person) in.readObject();
            in.close();
        } catch (Exception ex) {
            ex.printStackTrace();
        }
        System.out.println(p);
    }
}

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4. Links and Literature

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Copyright © 2012-2016 vogella GmbH. Free use of the software examples is granted under the terms of the EPL License. This tutorial is published under the Creative Commons Attribution-NonCommercial-ShareAlike 3.0 Germany license.

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