Java 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 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

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.

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();
      out.close();
    } catch (Exception ex) {
      ex.printStackTrace();
    }
    System.out.println(p);
  }
}