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0) Serialization

+ SERIALIZATION
  - reading and writing of objects called "object serialization"
  - allows objects to communicate with sockets
  - allows objects to be saved for use in a later invocation 
    of a program
  - uses the ObjectInputStream and ObjectOutputStream classes to read
    and write objects

http://java.sun.com/docs/books/tutorial/essential/io/serialization.html

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1) How to Write to an ObjectOutputStream

+ WRITING TO THE ObjectOutputStream
  - The ObjectOutputStream constructor takes an output stream as a 
    parameter
  - create it just like any other stream
  - ObjectOutputStream has the special method writeObject() to 
    write objects to the stream
  - This example (from the Java Tutorial) writes a String and a Date
    object to a file:

    FileOutputStream out = new FileOutputStream("theTime");
    ObjectOutputStream s = new ObjectOutputStream(out);
    s.writeObject("Today");
    s.writeObject(new Date());
    s.flush();

  - the writeObject() method serializes the object, and serializes
    any objects pointed to by an object being serialized
  - *** An object must implement the Serializable interface to be 
    serializable.

http://java.sun.com/docs/books/tutorial/essential/io/serializing.html

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2) How to Read from an ObjectInputStream

+ READING FROM THE ObjectInputStream
  - just like reading from any other stream
  - has the special method readObject(), which reads and returns the
    object from the stream
  - This example reads back in the objects written in the previous
    example

    FileInputStream in = new FileInputStream("theTime");
    ObjectInputStream s = new ObjectInputStream(in);
    String today = (String)s.readObject();
    Date date = (Date)s.readObject();

  - ObjectInputStream must be constructed on another stream (an input 
    stream), just like ObjectOutputStream is constructed on an output
    stream 
  - the readObject() method deserializes the object and in the stream
    and recursively deserializes all objects reachable from the
    current object.  This maintains all relationships between objects

http://java.sun.com/docs/books/tutorial/essential/io/serializing.html

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3) Providing Serialization for your Objects

+ SERIALIZABILITY
  - object must implement the Serializable interface to be serializable
  - the Serializable interface has no methods; it just identifies
    serializable objects.  Thus just add "implements Serializable"
    to your class definition
  - here's an example: 

  public class MySerializableClass implements Serializable {
    ...
  }

+ HOW ARE OBJECTS SERIALIZED/DESERIALIZED?
  - the defaultWriteObject() method of ObjectOutputStream handles
    serialization
  - the defaultReadObject() method of ObjectInputStream handles
    deserialization
  - defaultWriteObject() writes out everything required to reconstruct
    the object, including:
      - class of the object
      - class signature
      - values of all non-transient and non-static members, 
        including members that refer to other objects

http://java.sun.com/docs/books/tutorial/essential/io/providing.html