Serialization

• a process in which current state of Object will be saved in stream of bytes
• converting an object into a byte stream, to be saved in different mediums

Uses

• Write to disk
• Store in memory
• Send byte stream to other platform over network
• Save in databases as Binary Large Object (BLOB)

Serializable Interface

• interface implemented when serialization is desired
  • Note that this is a Marker Interface
  • no methods must be defined to conform with it
• Tells the compiler that the current class instance requires conversion to byte stream

Note

• If a class implements Serializable, then all of the subclasses are Serializable automatically

• If the superclass didn’t implement Serializable

  • The default constructor will be invoked from the superclass
  • All fields will initialize with the default values

serialVersionUID

• version number associated to each serializable class by serialization runtime
• used during deserialization process to verify that the sender and receiver of a serialized object have loaded class for that object which is compatible with respect to serialization.
• a serialVersionUID field is not mandatory
• if a serialVersionUID is defined
  • the field should be type long and must be static and final
• if no serialVersionUID defined
  • the serialization runtime will calculate default value for the that class
  • this varies based on compiler implementation
  • advisable to define serialVersionUID

Non Converted Fields

• Excludes specific fields from being serialized
• use the transient modifier to exclude fields from being serialized
• another way is to use static which also excludes from serialization