Serialization in greater detail

1
Lecture 5

• Serialization in greater detail
• The new FrameEditorDemo
• Javadoc comments
• Java UI Managers, PLAF
• JDesktopPane

2
Serializing example

• // In actionPerformed(ActionEvent e) method.
• // code handles Save menuitem by storing a
• // serialized object to file.
• if (e.getActionCommand().equals("Save"))
• try
• FileOutputStream out new FileOutputStream(fnam
  e)
• ObjectOutputStream s new ObjectOutputStream(ou
  t)
• s.writeObject(mySerializableObject)
• s.flush()
• catch (Exception ex)
• System.out.println("Save exception.")
• ex.printStackTrace()

3
What is written

• Class identification information
• A unique identifier (called the SUID)
• Serialized contents of each field.
• Recursive. Not tricked by reference loops.
• Includes even private and static fields
• Excludes transient and non-Serializable fields.
• May generate NotSerializableExceptions.

4
Why isnt Class X Serializable?

• Class declared abstract or final. No way to
  instantiate such a class, which is what
  de-serialization does.
• Special/Secure classes like RunTime, System,
  ClassLoader
• Classes which depend essentially on other
  non-Serializable classes.
• javax.swing.plaf.ComponentUI?

5
NotSerializableExceptions

• Suppose A is Serializable and B is a subclass of
  A. Then B inherits the Serializable interface
  and cant get rid of it. The only way to prevent
  serialization is to throw an Exception.
• Several Swing components do this. Their
  behavior is too closely tied to non-Serializable
  PLAF components.

6
Custom Serialization

• Method 1 Declare as transient all fields which
  you do not want to serialize. Must declare all
  Serializable fields which would generate an
  Exception.
• Method 2 Add custom methods
• writeObject() etc.
• Method 3 throw NotSerException.

7
Custom Serialization II

• Traps references to exception-throwers may be
  hidden (private fields of ancestor classes
  addActionListener) or unexpected (JMenuBar
  creates a exception-throwing PopUpMenuUI when it
  is clicked on.) They may also be important in
  this case, you may not want to implement
  Serializable.The Runtime Object

8
New FrameEditorDemo

• Arranged in packages.
• Sample targetFrame (SquarePuzzleApp) doesnt
  throw exceptions anymore.
• Doesnt try to serialize menus or ActionListeners
  anymore.
• ActionListeners are handled directly by the
  SquarePuzzleApp, not by Jbuttons now.

9
Before
10
After
Relayed ActionEvent
ActionEvents
11
The Point
Throw Exceptions
This relationship is transient (but
easily reinstated)
IsAn Action Listener
Serializable
View Code
12
Javadoc

• Automatic API generation system.
• By default, generates a frame-based class and
  package website. Can be customized to produce
  other formats than HTML.
• Generates docs from specially formatted
  comments. Should have one for each field and
  method of each class.

13
Doc Comments

• A doc comment is made up of two parts -- a
  description followed by zero or more tags, with a
  blank line (containing a single asterisk "")
  between these two sections /
  
  This is the description part. It can
  be any number of lines.
  
  
  _at_tag Comment for the tag /

14
Javadoc Markup

• Any HTML (carefully), esp. ltpgt
• _at_author, _at_version
• _at_param, _at_return
• _at_deprecated, _at_throws
• _at_serial
• _at_link, _at_see

15
Running Javadoc

• javadoc packagenames sourcenames
• Either run javadoc from parent directory of
  source tree or type absolute pathnames for
  packages and sources.
• Ex javadoc docdemo or javadoc
  C\files\desktop\Demo\DD\docdemo
• Leave html files in same directory structure.

16
The JDesktopPane class

• Parent JLayeredPane. Can hold multiple
  overlapping internal frames.
• Internal frames may be dragged, resized,
  iconified. These events are handled by a
  DesktopManager object.
• Demo

17
JDesktopPane Pro Con

• Gives more control over window behavior than
  JFrames. Can control minimization, window look
  and feel.
• Appearance same on all platforms, easily
  configurable.
• Requires more management. Cant just add
  components without saying where. Minimization
  prefs.

18
Extra Fields in JInternalFrame

• closable, closed, desktopIcon, desktopPane,
  frameIcon, icon, iconifiable, layer, layeredPane,
  maximizable, maximum, resizable, selected

19
Pluggable Look and Feel

• The JFC Swing UI building blocks are designed
  around a Pluggable Look and Feel architecture
  that allows us for the first time to get away
  from interpreting the visual manifestations, and
  instead plug in a non-visual manifestation.
  This architecture separates the expression of the
  UI from the underlying structure and data on a
  component-by-component basis.

20
Pluggable Look and Feel

• This is accomplished by separating the user
  interface of the component from the model of
  the component (the structure which encapsulates
  the state and information that the user interface
  portion presents to the user).

21
PLAF advantages

• Better platform independence. Mac users
  automatically get Mac LF, PC users get Windows
  LF, etc.
• Accessibility. Specialized LF can present in
  braille or audio output which was not specially
  formatted for this purpose.
• Convenience. UI easier to write.

22
PLAF how?

• Each Swing component has 5 objects needed to
  make it pluggable.
• Component itself (e.g. button)
• API for the buttonUI
• A default implementation buttonUI
• API for a Button model
• A default implementation JButton

23
Using the UIManager

• UIManager.setLookAndFeel(LNF) changes the
  default LF for new components.
  UIManager.getblahblahLookAndFeelClassName() can
  be used as an argument to this call.
• SwingUtilities.updateComponentTreeUI(frame)
  updates LF for existing frame
• frame.pack() resizes draws the frame.

24
Course Project

• First Checkpoint is next Fridayone every week.