Patterns in Eclipse

Madhu Samuel | eclipseBible.com Patterns in Eclipse

Pattern Recognition Machine Brain 

Patterns of Sound Waves

Our Craft Software Development

Problem!

What is the one constant in Software Development?

Change!

Patterns “ A proven way of solving a problem” Solution

Motivation for Patterns “ Separate things that change from things that stay the same”

Inheritance – “is a” Car Maruti Zen Tata Indica

Composition – “has a” Car Steering Wheel

Goal Loosely Coupled Systems

Patterns Creational Structural Behavioral Creational

Creational Patterns To isolate object creation from the rest of the application.

Structural Patterns To realize the relationship between objects .

Behavioral Patterns To realize the communication between objects .

Patterns
Singleton
Observer
Strategy
Composite
Proxy
Visitor
Memento
IAdaptible
Creational
Structural
Behavioral

Singleton Pattern in Platform Services

One and only one object
One Global Point of Access

PlatformUI . getWorkbench () ;
Platform . getWS ()

Observer Pattern in Workspace Listener

Subject Observer - 1 Observer - 2 Observer - n “ When the subject’s state changes, the subject notifies all the observers about the event” notifies

addResourceChangeListener()
removeResourceChangeListener()
IWorkspace
resourceChanged (ResourceChangeEvent)
IResourceChangeListener Sample_Observer Subject Observers
addResourceChangeListener()
removeResourceChangeListener()
IWorkspace

Strategy Pattern & Viewers

TableViewer Requirement : Add Sort Behavior
sort()

TableViewer Requirement : Add Multiple Sort Behavior
abstract sort()
TableViewerAlphaSort
sort()
TableViewerNumberSort
sort()

“ Strategy - Customize an object without subclassing”
setSorter()
TableViewer
sort()
ViewerSorter ViewerAlphaSorter
sort()
ViewerNumberSorter
sort()

“ Strategy pattern allows to change the behavior at runtime.”

Composite Pattern in SWT

“ Objects are grouped in a tree structure using Composition ” CheckBox Shell Group RadioButton

Widget Control Label Button abstract Button Composite 0..* Shell shell = new Shell(); new Button(shell, SWT. NONE ); getChildren()

Proxy Pattern in Eclipse File System

Dictionary a person autorized to act for another OOP an Object autorized to act for another Eclipse “ IFile” is autorized to act for “ file system” Proxy

IFile FileSystem

IFile
IFolder
IProject
IWorkspaceRoot
The proxy objects ( Handles ),

Value Objects
No state info.
Created from a parent Handle. “ IProject project; IFolder folder = project. getFolder (“myFolder”);
Create resources. “folder.create(“myPath”);”
Handle Characteristics

IFile File API Non-API Proxy!

You can navigate the tree of files in NO time! Advantage :

Visitor Pattern in Workspace Traversal

IProject IFolder IFile

filter()
IProject
filter()
IFolder
filter()
IFile OR!

Visitor Pattern “ Add a new operation to a structure of objects, without changing the objects”

IProject IFolder IFolder IFile IFile IFile Visitor

Visitor Object
Traversal Mechanism

accept(IResourceVisitor)
IResource
visit(IResource)
IResourceVisitor ElementTree ElementTreeIterator

Memento Pattern & Workbench State

“ Without violating encapsulation, Save an object’s internal state to restore later”
saveState(Memento)
restoreState(Memento)
WorkBench IMemento

IAdaptable

IFile IPropertySource Non-UI UI IFile IFile IFile IPropertySource IFile

1. How to add IPropertySource to IFile without exposing it in the type? 2. How to add new behavior to IFile?

Extension Object Pattern “ Extension object lets you add interfaces to a class”

IAdaptable getAdapter(Class adapter); IFile

public interface IAdaptable { public Object getAdapter ( class adapter); } ( IPropertySource ) file. getAdapter ( IPropertySource . class ); IPropertySource propertySource =

IAdaptable getAdapter(Class adapter); IFile AdapterManager adapter AdapterFactory 0..*

Object getAdatper(Object object, class adapter) { if(adapter.equals(IPropertySource.class) { return new FilePropertySource ((IFile)object); } }

Eclipse Training
Eclipse Plugin Development
RCP - Rich Client Platform
EMF - Eclipse Modeling Framework
GEF - Graphical Editing Framework
Java

Advanced - Training
How to write good code?
Architecture Patterns for Rich Client Applications
Architecture case studies of open source RCP apps.
Design Principles & Patterns

EclipseBible.com - Beta!

References
Eclipse Platform Source
Contributing to Eclipse : Principles, patterns and plugins
Head First Design Patterns
Design Patterns for Dummies
Google Images – images.google.com
Eclipse Corner Articles
EclipseBible.com

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Patterns in Eclipse

by Madhu Samuel on Apr 28, 2010

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