1. Satzinger, Jackson, and Burd Object-Orieneted Analysis & Design
Design Patterns
Satzinger, Jackson, and Burd
Object-Orieneted Analysis & Design

2. Summary Slide Importance of Design Patterns Basic Design Patterns
Designing Enterprise-level Systems
Differences between client/server and Internet systems
UML Notation for Deployment Diagrams
Simple Internet Architecture
Two-layer Architecture
Three-layer Architecture
Web Services

3. Importance of Design Patterns
Standard design templates can speed OO design
Patterns can exist at different levels of abstraction
At the most concrete level, a class definition with code
At the most abstract level, an approach to a problem
Patterns should contain five main elements
Pattern name, problem, solution, example, benefits and consequences

4. Pattern description for the controller pattern

5. Basic Design Patterns
The authors of Elements of Reusable Object-Oriented Software (referred to as the Gang of Four) developed a basic classification scheme for patterns
The 23 GoF patterns are some of the most fundamental and important patterns in use
Scores of other patterns have been defined
For example, both Java and .NET have sets of enterprise patterns

6. Singleton Pattern
For classes that must have only one instance, but need to be invoked from several classes and locations within the system
The class itself controls the creation of only one instance
A static variable of the class refers to the object that is created
A class method instantiates the object on the first call, and returns a reference to the object on subsequent calls

7. Singleton pattern template

8. Adaptor Pattern Plugs an external class into a system
Converts the method calls from within the system to match the method names in the external class
A standard solution for protection from variations
Insulates the system from frequently changing classes
An interface is frequently used to specify and enforce the use of correct method names

9. Adapter pattern template

10. Observer pattern Used to handle event-processing and reduce coupling
The domain class
Allows other classes to “subscribe” as listeners
“Publishes” the changes to the listeners
The windows class
Sends a reference of itself to subscribe as a listener
Implements the method to be invoked when notified
Inherits the method from the listener interface

11. Three classes in the Create new order use case
Figure 9-11
Three classes in the Create new order use case

12. Implementation of the observer pattern
Figure 9-12
Implementation of the observer pattern

13. Observer pattern template

14. Designing Enterprise-level Systems
Enterprise-level systems share components among multiple people or groups in an organization
Enterprise-level systems almost always use multiple tiers of computers
Can be client/server network-based or Internet based
Designed with deployment diagrams
A type of implementation diagram that shows physical components across different locations

15. Differences between client/server and Internet systems

16. UML Notation for Deployment Diagrams
Component
Executable module or program
Has an application program interface (API) that is available to the outside world
Node
A physical entity at a specific location
Frameset
A high-level object that holds items to be displayed by a browser

17. UML component notation

18. UML node notation
UML extension for frameset

19. Simple Internet Architecture
Used for viewing static information
The browser component executes on the client computer
The Internet server component executes on the server computer
Pages reside on the server and are sent to the browser for display
Program logic is inserted through scripting languages, applets, or other controls

20. Simple Internet architecture

21. Two-layer Architecture
Primarily captures information from the user and updates the database
The domain layer and data access layer are usually combined
Input data is sent to a CGI or an application server
The user-interface classes often contain the business logic and data access
Processing takes place with servlets (Java) or code behind classes (.NET)

22. Two-layer Internet architecture

23. Three-layer Architecture
Separates domain layer and data access layers
Necessary for systems with complex business logic or multiple user interfaces
Using CGI
Provide a use case controller for each form
Using an application server
Java tools: Java Server Pages and servlets
.NET tools: Common Runtime Language and code behind classes

24. Internet architecture
Three-layer
Internet architecture

25. Web Services A program that provides a service via the Internet
The service is posted in a directory so that systems can find it
Requests for information go to the UDDI directory
UDDI provides the Internet address of a program offering that service
The application then requests the information
All communication is based on XML to allow for generic data exchange

26. Invoking a Web service