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The Command Dispatcher Pattern Benoit Dupire and Eduardo B Fernandez {[email protected], [email protected]}
The Command Dispatcher Pattern Benoit Dupire and Eduardo B Fernandez {[email protected], [email protected]} Department of Computer Science and Engineering. Florida Atlantic University Boca Raton, FL 33431 Can also be called: Command Evaluator Pattern. Intent This pattern increases the flexibility of applications by enabling their services to be changed, by adding, replacing or removing any command handlers at any point in time without having to modify, recompile or statically relink the application. By simulating the command-evaluation feature common in interpreted languages, this pattern supports the need for continual, incremental evolution of applications. Example Autonomous Underwater Vehicles (AUVs) are small, unmanned, untethered submersibles. There are numerous applications for AUVs, such as oceanographic surveys, operations in hazardous environments, underwater structure inspection and military operations. We implement the high level controller of this AUV as a Hierarchical Finite State Machine (Figure 1). A state of the Finite State Machine (FSM) represents a mode of the system, in which some tasks have to be executed, as described in the mission plan. The system takes transitions based on the results of these actions and the progression of the AUV. The system is programmed with high-level commands of the style "set depth 3" state1 state2 action 1.1 action 2.1 Figure 1: Simplified Finite State Machine for the AUV. The FSM must be able to fire any type of actions, without knowing anything about them. This problem is addressed by the Command Pattern [GOF95], which encapsulates an action as an object, thereby letting you parameterize clients with different actions. -
Enterprise Development with Flex
Enterprise Development with Flex Enterprise Development with Flex Yakov Fain, Victor Rasputnis, and Anatole Tartakovsky Beijing • Cambridge • Farnham • Köln • Sebastopol • Taipei • Tokyo Enterprise Development with Flex by Yakov Fain, Victor Rasputnis, and Anatole Tartakovsky Copyright © 2010 Yakov Fain, Victor Rasputnis, and Anatole Tartakovsky.. All rights reserved. Printed in the United States of America. Published by O’Reilly Media, Inc., 1005 Gravenstein Highway North, Sebastopol, CA 95472. O’Reilly books may be purchased for educational, business, or sales promotional use. Online editions are also available for most titles (http://my.safaribooksonline.com). For more information, contact our corporate/institutional sales department: (800) 998-9938 or [email protected]. Editor: Mary E. Treseler Indexer: Ellen Troutman Development Editor: Linda Laflamme Cover Designer: Karen Montgomery Production Editor: Adam Zaremba Interior Designer: David Futato Copyeditor: Nancy Kotary Illustrator: Robert Romano Proofreader: Sada Preisch Printing History: March 2010: First Edition. Nutshell Handbook, the Nutshell Handbook logo, and the O’Reilly logo are registered trademarks of O’Reilly Media, Inc. Enterprise Development with Flex, the image of red-crested wood-quails, and related trade dress are trademarks of O’Reilly Media, Inc. Many of the designations used by manufacturers and sellers to distinguish their products are claimed as trademarks. Where those designations appear in this book, and O’Reilly Media, Inc. was aware of a trademark claim, the designations have been printed in caps or initial caps. While every precaution has been taken in the preparation of this book, the publisher and authors assume no responsibility for errors or omissions, or for damages resulting from the use of the information con- tained herein. -
APPLYING MODEL-VIEW-CONTROLLER (MVC) in DESIGN and DEVELOPMENT of INFORMATION SYSTEMS an Example of Smart Assistive Script Breakdown in an E-Business Application
APPLYING MODEL-VIEW-CONTROLLER (MVC) IN DESIGN AND DEVELOPMENT OF INFORMATION SYSTEMS An Example of Smart Assistive Script Breakdown in an e-Business Application Andreas Holzinger, Karl Heinz Struggl Institute of Information Systems and Computer Media (IICM), TU Graz, Graz, Austria Matjaž Debevc Faculty of Electrical Engineering and Computer Science, University of Maribor, Maribor, Slovenia Keywords: Information Systems, Software Design Patterns, Model-view-controller (MVC), Script Breakdown, Film Production. Abstract: Information systems are supporting professionals in all areas of e-Business. In this paper we concentrate on our experiences in the design and development of information systems for the use in film production processes. Professionals working in this area are neither computer experts, nor interested in spending much time for information systems. Consequently, to provide a useful, useable and enjoyable application the system must be extremely suited to the requirements and demands of those professionals. One of the most important tasks at the beginning of a film production is to break down the movie script into its elements and aspects, and create a solid estimate of production costs based on the resulting breakdown data. Several film production software applications provide interfaces to support this task. However, most attempts suffer from numerous usability deficiencies. As a result, many film producers still use script printouts and textmarkers to highlight script elements, and transfer the data manually into their film management software. This paper presents a novel approach for unobtrusive and efficient script breakdown using a new way of breaking down text into its relevant elements. We demonstrate how the implementation of this interface benefits from employing the Model-View-Controller (MVC) as underlying software design paradigm in terms of both software development confidence and user satisfaction. -
Behavioral Patterns
Behavioral Patterns 101 What are Behavioral Patterns ! " Describe algorithms, assignment of responsibility, and interactions between objects (behavioral relationships) ! " Behavioral class patterns use inheritence to distribute behavior ! " Behavioral object patterns use composition ! " General example: ! " Model-view-controller in UI application ! " Iterating over a collection of objects ! " Comparable interface in Java !" 2003 - 2007 DevelopIntelligence List of Structural Patterns ! " Class scope pattern: ! " Interpreter ! " Template Method ! " Object scope patterns: ! " Chain of Responsibility ! " Command ! " Iterator ! " Mediator ! " Memento ! " Observer ! " State ! " Strategy ! " Visitor !" 2003 - 2007 DevelopIntelligence CoR Pattern Description ! " Intent: Avoid coupling the sender of a request to its receiver by giving more than one object a chance to handle the request. Chain the receiving objects and pass the request along the chain until an object handles it. ! " AKA: Handle/Body ! " Motivation: User Interfaces function as a result of user interactions, known as events. Events can be handled by a component, a container, or the operating system. In the end, the event handling should be decoupled from the component. ! " Applicability: ! " more than one object may handle a request, and the handler isn't known a priori. ! " Want to issue a request to one of several objects without specifying the receiver !" 2003 - 2007 DevelopIntelligence CoR Real World Example ! " The Chain of Responsibility pattern avoids coupling the sender of a request to the receiver, by giving more than one object a chance to handle the request. ! " Mechanical coin sorting banks use the Chain of Responsibility. Rather than having a separate slot for each coin denomination coupled with receptacle for the denomination, a single slot is used. When the coin is dropped, the coin is routed to the appropriate receptacle by the mechanical mechanisms within the bank. -
Design Patterns in Ocaml
Design Patterns in OCaml Antonio Vicente [email protected] Earl Wagner [email protected] Abstract The GOF Design Patterns book is an important piece of any professional programmer's library. These patterns are generally considered to be an indication of good design and development practices. By giving an implementation of these patterns in OCaml we expected to better understand the importance of OCaml's advanced language features and provide other developers with an implementation of these familiar concepts in order to reduce the effort required to learn this language. As in the case of Smalltalk and Scheme+GLOS, OCaml's higher order features allows for simple elegant implementation of some of the patterns while others were much harder due to the OCaml's restrictive type system. 1 Contents 1 Background and Motivation 3 2 Results and Evaluation 3 3 Lessons Learned and Conclusions 4 4 Creational Patterns 5 4.1 Abstract Factory . 5 4.2 Builder . 6 4.3 Factory Method . 6 4.4 Prototype . 7 4.5 Singleton . 8 5 Structural Patterns 8 5.1 Adapter . 8 5.2 Bridge . 8 5.3 Composite . 8 5.4 Decorator . 9 5.5 Facade . 10 5.6 Flyweight . 10 5.7 Proxy . 10 6 Behavior Patterns 11 6.1 Chain of Responsibility . 11 6.2 Command . 12 6.3 Interpreter . 13 6.4 Iterator . 13 6.5 Mediator . 13 6.6 Memento . 13 6.7 Observer . 13 6.8 State . 14 6.9 Strategy . 15 6.10 Template Method . 15 6.11 Visitor . 15 7 References 18 2 1 Background and Motivation Throughout this course we have seen many examples of methodologies and tools that can be used to reduce the burden of working in a software project. -
Design Pattern Implementation in Java and Aspectj
Design Pattern Implementation in Java and AspectJ Jan Hannemann Gregor Kiczales University of British Columbia University of British Columbia 201-2366 Main Mall 201-2366 Main Mall Vancouver B.C. V6T 1Z4 Vancouver B.C. V6T 1Z4 jan [at] cs.ubc.ca gregor [at] cs.ubc.ca ABSTRACT successor in the chain. The event handling mechanism crosscuts the Handlers. AspectJ implementations of the GoF design patterns show modularity improvements in 17 of 23 cases. These improvements When the GoF patterns were first identified, the sample are manifested in terms of better code locality, reusability, implementations were geared to the current state of the art in composability, and (un)pluggability. object-oriented languages. Other work [19, 22] has shown that implementation language affects pattern implementation, so it seems The degree of improvement in implementation modularity varies, natural to explore the effect of aspect-oriented programming with the greatest improvement coming when the pattern solution techniques [11] on the implementation of the GoF patterns. structure involves crosscutting of some form, including one object As an initial experiment we chose to develop and compare Java playing multiple roles, many objects playing one role, or an object [27] and AspectJ [25] implementations of the 23 GoF patterns. playing roles in multiple pattern instances. AspectJ is a seamless aspect-oriented extension to Java, which means that programming in AspectJ is effectively programming in Categories and Subject Descriptors Java plus aspects. D.2.11 [Software Engineering]: Software Architectures – By focusing on the GoF patterns, we are keeping the purpose, patterns, information hiding, and languages; D.3.3 intent, and applicability of 23 well-known patterns, and only allowing [Programming Languages]: Language Constructs and Features – the solution structure and solution implementation to change. -
A Design Pattern Generation Tool
Project Number: GFP 0801 A DESIGN PATTERN GEN ERATION TOOL A MAJOR QUALIFYING P ROJECT REPORT SUBMITTED TO THE FAC ULTY OF WORCESTER POLYTECHNIC INSTITUTE IN PARTIAL FULFILLME NT OF THE REQUIREMEN TS FOR THE DEGREE OF BACHELOR O F SCIENCE BY CAITLIN VANDYKE APRIL 23, 2009 APPROVED: PROFESSOR GARY POLLICE, ADVISOR 1 ABSTRACT This project determines the feasibility of a tool that, given code, can convert it into equivalent code (e.g. code that performs the same task) in the form of a specified design pattern. The goal is to produce an Eclipse plugin that performs this task with minimal input, such as special tags.. The final edition of this plugin will be released to the Eclipse community. ACKNOWLEGEMENTS This project was completed by Caitlin Vandyke with gratitude to Gary Pollice for his advice and assistance, as well as reference materials and troubleshooting. 2 TABLE OF CONTENTS Abstract ....................................................................................................................................................................................... 2 Acknowlegements ................................................................................................................................................................... 2 Table of Contents ..................................................................................................................................................................... 3 Table of Illustrations ............................................................................................................................................................. -
Java Design Patterns I
Java Design Patterns i Java Design Patterns Java Design Patterns ii Contents 1 Introduction to Design Patterns 1 1.1 Introduction......................................................1 1.2 What are Design Patterns...............................................1 1.3 Why use them.....................................................2 1.4 How to select and use one...............................................2 1.5 Categorization of patterns...............................................3 1.5.1 Creational patterns..............................................3 1.5.2 Structural patterns..............................................3 1.5.3 Behavior patterns...............................................3 2 Adapter Design Pattern 5 2.1 Adapter Pattern....................................................5 2.2 An Adapter to rescue.................................................6 2.3 Solution to the problem................................................7 2.4 Class Adapter..................................................... 11 2.5 When to use Adapter Pattern............................................. 12 2.6 Download the Source Code.............................................. 12 3 Facade Design Pattern 13 3.1 Introduction...................................................... 13 3.2 What is the Facade Pattern.............................................. 13 3.3 Solution to the problem................................................ 14 3.4 Use of the Facade Pattern............................................... 16 3.5 Download the Source Code............................................. -
Design Patterns
CSE 403: Software Engineering, Winter 2016 courses.cs.washington.edu/courses/cse403/16wi/ Design Patterns Emina Torlak [email protected] Outline • Overview of design patterns • Creational patterns • Structural patterns • Behavioral patterns 2 introoverview of design patterns What is a design pattern? 4 What is a design pattern? • A standard solution to a common programming problem • a design or implementation structure that achieves a particular purpose • a high-level programming idiom 4 What is a design pattern? • A standard solution to a common programming problem • a design or implementation structure that achieves a particular purpose • a high-level programming idiom • A technique for making code more flexible or efficient • reduce coupling among program components • reduce memory overhead 4 What is a design pattern? • A standard solution to a common programming problem • a design or implementation structure that achieves a particular purpose • a high-level programming idiom • A technique for making code more flexible or efficient • reduce coupling among program components • reduce memory overhead • Shorthand for describing program design • a description of connections among program components • the shape of a heap snapshot or object model 4 Why should you care? • You could come up with these solutions on your own … • But you shouldn't have to! • A design pattern is a known solution to a known problem. 5 Types of design patterns • Creational patterns • how objects are instantiated • Structural patterns • how objects / classes can -
Object-Oriented Design Patterns
Object-Oriented Design Patterns David Janzen EECS 816 Object-Oriented Software Development University of Kansas Outline • Introduction – Design Patterns Overview – Strategy as an Early Example – Motivation for Creating and Using Design Patterns – History of Design Patterns • Gang of Four (GoF) Patterns – Creational Patterns – Structural Patterns – Behavioral Patterns Copyright © 2006 by David S. 2 Janzen. All rights reserved. What are Design Patterns? • In its simplest form, a pattern is a solution to a recurring problem in a given context • Patterns are not created, but discovered or identified • Some patterns will be familiar? – If you’ve been designing and programming for long, you’ve probably seen some of the patterns we will discuss – If you use Java Foundation Classes (Swing), Copyright © 2006 by David S. 3 you have certaJiannzleyn. Aulls rieghdts rsesoervmed.e design patterns Design Patterns Definition1 • Each pattern is a three-part rule, which expresses a relation between – a certain context, – a certain system of forces which occurs repeatedly in that context, and – a certain software configuration which allows these forces to resolve themselves 1. Dick Gabriel, http://hillside.net/patterns/definition.html Copyright © 2006 by David S. 4 Janzen. All rights reserved. A Good Pattern1 • Solves a problem: – Patterns capture solutions, not just abstract principles or strategies. • Is a proven concept: – Patterns capture solutions with a track record, not theories or speculation 1. James O. Coplien, http://hillside.net/patterns/definition.html Copyright © 2006 by David S. 5 Janzen. All rights reserved. A Good Pattern • The solution isn't obvious: – Many problem-solving techniques (such as software design paradigms or methods) try to derive solutions from first principles. -
Design Patterns
Principles of Software Construction: Objects, Design, and Concurrency Introduction to Design Patterns Charlie Garrod Chris Timperley 17-214 1 Administrivia • Homework 1 feedback in your GitHub repository • Homework 2 due tonight 11:59 p.m. • Homework 3 available tomorrow • Optional reading due today: Effective Java Items 18, 19, and 20 – Required reading due next Tuesday: UML & Patterns Ch 9 and 10 17-214 2 Key concepts from Tuesday 17-214 3 Delegation vs. inheritance summary • Inheritance can improve modeling flexibility • Usually, favor composition/delegation over inheritance – Inheritance violates information hiding – Delegation supports information hiding • Design and document for inheritance, or prohibit it – Document requirements for overriding any method 17-214 4 Continued: instanceof • Operator that tests whether an object is of a given class public void doSomething(Account acct) { long adj = 0; if (acct instanceof CheckingAccount) { Do not checkingAcct = (CheckingAccount) acct; adj = checkingAcct.getFee(); do this. } else if (acct instanceof SavingsAccount) { savingsAcct = (SavingsAccount) acct; This code adj = savingsAcct.getInterest(); is bad. } … } • Advice: avoid instanceof if possible – Never(?) use instanceof in a superclass to check type against subclass 17-214 5 Continued: instanceof • Operator that tests whether an object is of a given class public void doSomething(Account acct) { long adj = 0; if (acct instanceof CheckingAccount) { Do not checkingAcct = (CheckingAccount) acct; adj = checkingAcct.getFee(); do this. } -
Design Patterns for Developing Dynamically Adaptive
Design Patterns for Developing Dynamically Adaptive Systems ∗ Andres J. Ramirez and Betty H.C. Cheng Michigan State University 3115 Engineering Building East Lansing, Michigan 48824 {ramir105, chengb}@cse.msu.edu ABSTRACT 1. INTRODUCTION As applications grow in size and complexity, and computing As applications grow in size, complexity, and heterogene- infrastructure continues to evolve, it becomes increasingly ity in response to growing computational needs, it is increas- difficult to build a system that satisfies all requirements and ingly difficult to build a system that satisfies all require- constraints that might arise during its lifetime. As a result, ments and design constraints that it will encounter during there is an increasing need for software to adapt in response its lifetime. Many of these systems are required to run con- to new requirements and environmental conditions after it tinuously, disallowing long downtimes where humans look has been deployed. Due to their high complexity, adaptive for places to modify the code. As a result, it is important programs are generally difficult to specify, design, verify, and to be able to adapt an application’s behavior at run time in validate. In addition, the current lack of reusable design ex- response to changing requirements and environmental condi- pertise that can be leveraged from one adaptive system to tions [21]. IBM proposed autonomic computing [16] to meet another further exacerbates the problem. To address this this need, where a system manages itself based on high-level problem, we studied over thirty adaptation-related research objectives from a systems administrator, thus promoting and project implementations available from the literature self-management and self-reconfiguration.