Serialization

• Serialized class: A class which implements Serializable interface.
• Persistence: saving an object to a permanent storage.
• Only the object’s data are serialized.
• Data marked with the transient keyword are not serialized.
• Make a class serializable.
• Write an object to a file.
• Read an object from a file.

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Make a class serializable

• Serializable interface: a mark interface; no method needed to implement.
• Example:

  class Test implements Serializable {
      transient int SSN;//not serialized
      double d;
      String s;
      Test() {
          ....
      }
  
  }
  

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Write an object to a file

• Use ObjectOutputStream

  AnObject d = new AnObject();
  try {
      FileOutputStream f = new FileOutputStream ("data.ser");
      ObjectOutputStream s = new ObjectOutputStream (f);
      s.writeObject (d);
      s.close ();
   } catch (IOException e) {}
  

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Read an Object from a file

• Use ObjectInputStream

  try {
      FileInputStream f = new FileInputStream ("data.ser");
      ObjectInputStream s = new ObjectInputStream (f);
      d = (ObjectType) s.readObject ();
      s.close ();
   } catch (Exception e) {}
  

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