Java object serialization

 

Java object serialization

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

 

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Table of Contents

1. Java Serialization

2. Example

3. About this website

3.1.

4. Links and Literature

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);
  }
}