Techniques & Patterns For Writing Once And Running Anywhere

Objectives:

• Describe design alternatives that overcome weaknesses in Java and in developing Java for the Web.

• Describe techniques and patterns to help developers write platform-independent Java code.

Example: On one project, Industrial Logic noticed that it had almost 200K in objects and interfaces. We had an extreemely flexible implementation, but it was too damn big! We later got the total size down to 92K.

Example:

Patterns may make you rich.

artist: Jay Munro, originally printed in DOC Magazine

Other patterns and techniques used:

• Doug Lea's "Concurrent Programming in Java: Design Principles and Patterns"
• Javascript: for controlling browser windows and parameter passing
• Factory Method
• Abstract Factory
• Decorator

Sample Usage:

  public class MyCommand
    extends Object implements ili_Command
  {
    protected ili_Context _context;
    public MyCommand() { }

    public void init(ili_Context context)
    { _context = context; }

    public void execute(String id)
    {
      // do something useful
    }
  }

MacroCommand: Run Multiple Commands

public class MacroCommand
 extends Object implements ili_CommandI
{
  protected ili_ListEnumerator _parms;
  ...
  public void execute(String id)
  {
    ...
    _parms = _context.getListEnumerator(id);
    try
    {
      while ( _parms!=null &&
              _parms.hasMoreElements() )
      {
         _context.execute(
           _parms.nextElement().toStr() );
      }
    }
    catch (Throwable e)
    {
      ... exception handling code
    }
  }
}