What is Java Object Serilization

Supports the transformation of a graph of java objects into a stream of bytes for storage or transmission.

Serialisation - Objects gets transformed into byte stream. Deserialisation - Bytes can be transformed into a graph of java objects.

Serializable Classes

• Save and restored fields of each object.
• Allow classes to evolve by adding field or superclasses.

A serializable class can be

• Declare which of its fields are saved or restored.
• Write and read optional values and objects.

By default, non-transient and non-static fields are serialized. Transient fields are fields those have meant to be non-persistent.

Object Output Serialization

• Implements object serialization
• Maintains the state of the stream including the objects already serialized.
• Write object method used to serialize an object to the stream.

Note: Only data is stored in a serialization byte stream. - Code is not serialization

JVM in order to de-serialization of an object needs to identify the objects into the class definition it has access to.

The write object method

• The specified object
• Traverses references to other objects in the object graph recursively to create a complete serialized representation of the graph.

Primitive types (int, float, bytes, arrays) can also be serialized.