2 Object-Oriented Analysis and Design with the Unified Process Objectives  Explain how statecharts can be used to describe system behaviors  Use statecharts to model system behavior and method logic  Explain the importance of design patterns in object- oriented design  Briefly describe and use the singleton, adaptor, and observer design patterns

3 Object-Oriented Analysis and Design with the Unified Process Objectives (continued)  Explain why enterprise-level systems require special design consideration  Apply UML deployment architectural notation to Web-based systems  Explain how Web services work to obtain information on the Internet

4 Object-Oriented Analysis and Design with the Unified Process Overview  Model system and object behavior  Statecharts  Protect and stabilize systems  Protection from variations and indirection  Establish best practices in system construction  Design patterns, or templates  Design for enterprise-level and Web-based systems  Distributed and networked environments

5 Object-Oriented Analysis and Design with the Unified Process Modeling System Behavior and Method Logic with Statecharts  Statecharts were used in the requirements discipline to capture status conditions of objects  Statecharts are used in the design discipline to  Define the behavioral constraints of the system classes created during design ◘Windows menus, authentication and security classes, error-handling classes  Describe the method logic within class methods ◘Action-expressions contain information that help define method logic

6 Object-Oriented Analysis and Design with the Unified Process System-level Statecharts  Designate the states and processing controls of a system  Which menu items are enabled or disabled  Which windows are modal  Which tool bars and icons are active  Document possible options presented to users  Use state variables to record the value of the current state

7 Object-Oriented Analysis and Design with the Unified Process Figure 9-1 Logon statechart for a computer system

8 Object-Oriented Analysis and Design with the Unified Process Messages, Transitions, and Methods  A message causes a transition to fire  A transition in a statechart is the execution of a method  A method signature is defined by the message to a destination object  Action expressions in a statechart define method logic  Describes the actions to be performed during a transition

9 Object-Oriented Analysis and Design with the Unified Process Figure 9-2 Comparison of methods, messages, and transitions

10 Object-Oriented Analysis and Design with the Unified Process Action-expressions and Method Logic  A sequence diagram may not contain enough internal details about a method  Design statecharts extend requirements statecharts  Action-expressions contain logic for later coding  Transitions that allow the object to remain in the same state  Temporary states for inter-model consistency  Decision pseudostates to indicate decision points on a paths

11 Object-Oriented Analysis and Design with the Unified Process Figure 9-4 Statechart for Order

12 Object-Oriented Analysis and Design with the Unified Process Figure 9-5 Design statechart for Order

13 Object-Oriented Analysis and Design with the Unified Process Design Principles-Protection From Variations  Parts of a system that are unlikely to change are segregated from those that will  Drives the multilayer design pattern  Stable business logic can be protected from variations in the user interface  Changes in the business logic are isolated to the controller class

14 Object-Oriented Analysis and Design with the Unified Process Design Principles-Indirection  Indirection is an implementation of the protection from variations principle  Decouples classes or other system components by placing an intermediate classes between them  Used in many corporate security systems between an internal network and the Internet  A proxy server catches all incoming messages and redistributes them to the recipients

15 Object-Oriented Analysis and Design with the Unified Process 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

16 Object-Oriented Analysis and Design with the Unified Process Figure 9-6 Pattern description for the controller pattern

17 Object-Oriented Analysis and Design with the Unified Process 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 (Figure 9-7)  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

18 Object-Oriented Analysis and Design with the Unified Process Figure 9-7 Classification of design patterns

19 Object-Oriented Analysis and Design with the Unified Process 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

20 Object-Oriented Analysis and Design with the Unified Process Figure 9-8 Singleton pattern template

21 Object-Oriented Analysis and Design with the Unified Process 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

22 Object-Oriented Analysis and Design with the Unified Process Figure 9-10 Adapter pattern template

23 Object-Oriented Analysis and Design with the Unified Process 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

24 Object-Oriented Analysis and Design with the Unified Process Figure 9-11 Three classes in the Create new order use case

25 Object-Oriented Analysis and Design with the Unified Process Figure 9-12 Implementation of the observer pattern

26 Object-Oriented Analysis and Design with the Unified Process Figure 9-13 Observer pattern template

27 Object-Oriented Analysis and Design with the Unified Process 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

28 Object-Oriented Analysis and Design with the Unified Process Figure 9-14 Differences between client/server and Internet systems

29 Object-Oriented Analysis and Design with the Unified Process 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

30 Object-Oriented Analysis and Design with the Unified Process Figure 9-15 UML component notation

31 Object-Oriented Analysis and Design with the Unified Process Figure 9-16 UML node notation Figure 9-17 UML extension for frameset

32 Object-Oriented Analysis and Design with the Unified Process 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

33 Object-Oriented Analysis and Design with the Unified Process Figure 9-18 Simple Internet architecture

34 Object-Oriented Analysis and Design with the Unified Process 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)

35 Object-Oriented Analysis and Design with the Unified Process Figure 9-19 Two-layer Internet architecture

36 Object-Oriented Analysis and Design with the Unified Process 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

37 Object-Oriented Analysis and Design with the Unified Process Figure 9-20 Three-layer Internet architecture

38 Object-Oriented Analysis and Design with the Unified Process 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

39 Object-Oriented Analysis and Design with the Unified Process Figure 9-21 Invoking a Web service

40 Object-Oriented Analysis and Design with the Unified Process Summary  Design statecharts  Specify precise behavior and constraints of the various portions of the final system  Describe the method logic within an object  Good design is based on two factors  Good principles  Standard design patterns

41 Object-Oriented Analysis and Design with the Unified Process Summary (continued)  Protection from variations  Separates components that are likely to change  Indirection  Intermediate class provides an interface between elements  Design pattern examples  Singleton  Adaptor  Observer