Design Patterns
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05/26/2004 www.indyjug.net 1 Indy Java User’s Group June 29 2005 6:00p.m @ Knowledge Services, Inc.
description
Transcript of Design Patterns
05/26/2004 www.indyjug.net 1
Indy Java User’s Group
June 29 2005
6:00p.m
@ Knowledge Services, Inc.
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Agenda
•Welcome / Pizza 6:00-6:15
•Introductions 6:15-6:30
•Design Patterns 6:30-7:30
•Future JUG Topics 7:30-8:00
•Giveaways 8:00-8:15
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Mission Statement
Promote the use of the Java language and components across all levels of interest in the greater Indianapolis area, by serving as a resource for knowledge, experience and career opportunities.
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Introductions
•NameName
•WorkWork
•How long have you been How long have you been coming?coming?
•Something InterestingSomething Interesting
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Tonight’s Objective
•Design Patterns Overview
•Elements of a Design Patterns
•Chain of Responsibility(CoR) Example
•‘Your Turn’
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Design Patterns (Overview)
•Goals of Design Patterns
•Benefits of Design Patterns
•Challenges of Design Patterns
•History (Gang of Four)
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Design Patterns (Goal)
•“Capture solutions that have developed and evolved over time in a succinct and easily applied form.”
•“Systematically name, explain and evaluate an important and recurring design in object-oriented systems”
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Design Patterns (Quote)
“A design pattern isn’t ‘designed’. It’s discovered. In other words, patterns aren’t an invention as much as they are a refactoring of existing concepts.”
- A. Russell Jones
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Design Patterns (Benefits)
•Vocabulary
•Reusability
•OO Ideals
•Standardization
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Design Patterns (Challenges)
•“Define and describe a repetitive activity at a high enough level to be useful across very different applications, yet specific enough to have a single implementation.”
•Individual interpretation (Design vs. Impl)
•Terminology overloading.
•Implementation (language limitations, etc)
•Singleton example
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Design Patterns (Singleton)
public static MyObject getInstance(){
if( myObject == null ) {
myObject = new MyObject(this);
}
return( myObject );
}
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Design Patterns (History)
•Gang of Four•Erich Gamma, Richard Helm, Ralph Johnson, John Vlissides
•BookDesign Patterns:
Elements of Reusable Object-Oriented Software
•ISBN 0-201-63361-2
•Copyright 1995 by Addison Wesley, Inc.
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Design Patterns (Elements-1)
•Pattern Name (handle)•Higher level of abstraction•Vocabulary
•Problem (context)•Conditions that must be met before the pattern can be applied•Describe class or object structures
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Design Patterns (Elements-2)
•Solution (elements)•Relationships•Responsibilities•Collaborations
•Consequences (trade-off)•Flexibility•Extensibility•Portability
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Design Patterns (Categories)
•Creational Patterns Factory Method, Singleton, Abstract Factory, Builder, Prototype
•Structural PatternsAdapter, Decorator, Bridge, Composite, Façade, Flyweight, Proxy
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Design Patterns (Categories)
•Behavioral PatternsCommand, Iterator, Interpreter, Mediator,Chain of Responsibility (CoR), Memento, Observer, State, Strategy, Template Method, Visitor
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Design Patterns (Creational)
Creational design patterns abstract the instantiation process. They help make a system independent of how its objects are created, composed, and represented.
(Factory, Singleton)
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Design Patterns (Structural)
Structural design patterns are concerned with how classes and objects are composed to form larger structures. (i.e. Inheritance).
(Adapter, Decorator)
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Design Patterns (Behavioral)
Behavioral design patterns are concerned with algorithms and the assignment of responsibilities between objects including the communication between them.
(Command, Iterator)
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Design Patterns (Review)
Decorator •Allows the ability to change the ‘skin’
Strategy•Allows the ability to change the ‘guts’
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Design Patterns (CoR)
“Avoid coupling the sender of a request to its receiver by giving more then one object a chance to handle the request. Chain the receiving objects and pass the request along the chain until an object handles it.” -GoF
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Design Patterns
ExampleExample
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Design Patterns (References)
•www.javaworld.com/javaworld/jw-08-2004/jw-0816-chain_p.html
•www.devx.com/opinion/Article/22035/1954?pf=true
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Design Patterns
Your Turn!!Your Turn!!
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Future Topics
Recap from 11/2004:•Sitemesh•Subversion•RUP / XP / Agile•JNDI/LDAP•Clustering / Deploying various OSs•Webstart•PDF Generation•SOA/SOAP/Web Services
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Info
•Next Meeting - July 27, 2004•The Art of Agility and the AUP
- Agile unified Process -
•Discussion Forumhttp://groups.yahoo.com/group/indyjug
•Website - http://www.indyjug.net
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