1. Serialization and Deserialization Bullet points from Head First Java, Ch. 14
6-Dec-18
serialization.ppt

2. saving an object between program runs
you can save an object’s state by serializing the object
to serialize an object, you need an ObjectOutputStream (from the java.io package)
streams are either connection or chain streams
connection streams can represent a connection to a source or destination
typically a file, network socket connection, or the console
chain streams cannot connect to a source or destination
they must be chained to a connection (or other) stream
to serialize an object to a file, make a FileOutputStream and chain it into an ObjectOutputStream
to serialize an object, call writeOjbect(theObject) on the ObjectOutputStream
you do not need to call any methods on the FileOutputStream
6-Dec-18
serialization.ppt

3. Serializable interface
by default, objects are not serializable
to be serialized, an object must implement the Serializable interface
Serializable is an empty interface
it has no methods that must be implemented
its presence is a signal to the runtime that this object can be serialized
if a superclass of the class implements Serializable, the subclass can also be serialized
even without explicitly declaring implements Serializable
6-Dec-18
serialization.ppt

4. when an object is serialized, its entire object graph is serialized
the object graph
when an object is serialized, its entire object graph is serialized
including any objects referenced by the serialized object’s instance variables
plus any objects those objects reference, and so on
if any object in the graph is not serializable, an exception will be thrown at runtime
unless the instance variable referring to the un-serializable object is skipped
the transient keyword can be used to do mark an instance variable to be skipped
an instance variable marked as transient will be restored as null upon deserialization
or the default value for a primitive
6-Dec-18
serialization.ppt

5. the return type of readObject() is Object
deserialization
using readObject(), read objects in the order in which they were originally written
the return type of readObject() is Object
deserialized objects must be cast to their original type
static variables are not serializable
it doesn’t make sense to make static variables part of a particular object’s state, since all objects of that type (made from that class) share only a single static value
6-Dec-18
serialization.ppt

6. the end of this PowerPoint file
Hooray!
6-Dec-18
serialization.ppt