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Java Fundamentals - Persisting Objects

Serializing


Storing an objet-graph to a byte stream

Deserializing


Restoring an objet-graph from a byte stream

Serializing an Object


  • ObjectOutputStream

ObjectOutputStream out = new ObjectOutputStream( Files.newOutputStream (Path.get( filename )) );
out.writeObj ( object );



Deserializing an Object


  • ObjectInputStream

ObjectInputStream ois = new ObjectInputStream( Files.newInputStream (Path.get( filename )) );
ois.readObj ( );


Creating class version compatibility

  • In a propmt inside /bin from our JDK

  • Type:>   serialer  CLASS_PATH(Ej. com.comp.class)

or

  • Type: serialer -show 
To have a GUI

  • Delcare the field serialVersionUID as
private static final long serialVersionUID = (Result from previous step);

As long as all our classes contains the same serialVersionUID number will be compatible among them.


Compare version using Reflection

Once you get the ObjectOutputStream you can start using reflection.

ObjectOutputStream object = .....;
object.get("id", null);

In this case we are validating if this version contains the field Id 


Transient Fields

Use transient to avoid that some fields be serialized.

Ej. private transient int total;









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