The document discusses Java serialization, which allows objects to be saved as bytes that can be written to disk or transmitted over a network. It explains that serializing includes the object's entire graph, including attributes and contained objects that are also serializable. For a class to be serialized, it must implement the Serializable interface, have a no-arg constructor, and can optionally define a serialVersionUID for compatibility checks. The writeObject() and readObject() methods of ObjectOutputStream and ObjectInputStream are used to serialize and deserialize objects to and from a file.

1. Java Serialization
Sujit Kumar
Zenolocity LLC
Copyright 2012 – 2050 @

2. Serializable Interface
• Marker Interface => No methods.
• Indicates that objects of the class can be
persisted (saved) as bytes on disk or
transmitted over the network as bytes.
• Objects can be reconstructed using the bytes
saved on disk or bytes received over the
network.

3. What does Serializable include?
• The entire object graph => current object, super
class attributes and objects contained within the
current object.
• Includes all the instance attributes (objects or
primitive types) from the object which are also
serializable.
• Includes all the instance attributes from the super
classes which are serializable.
• Excluded instance attributes marked as transient.

4. Requirements
• Class should implement the serializable
interface.
• Class should have a no argument constructor.
• serialVersionUID (static final long) is optional
but recommended. Represents the version
number of the class and checks compatibility
of serialized objects with the current version
of the class.

5. How to serialize & deserialize?
• ObjectOutputStream => writeObject()
• Saving to a file on disk => Wrap a
FileOutputStream with an
ObjectOutputStream.
• ObjectInputStream => readObject()
• Read from a file on disk => Wrap a
FileInputStream with an ObjectInputStream.