COMP 7700 – Structural Design Patterns1Chapter 8Structural Design PatternsCOMP 7700 – Structural Design Patterns2Design PurposeProvide an interface to a package of classesDesign Pattern SummaryDefine a singleton which is the sole meansfor obtaining functionality from the package.FacadeNotes: the classes need not be organized as a package;more than one class may be used for the façade.Adapted from Software Design: From Programming to Architecture by Eric J. Braude (Wiley 2003), with permission.COMP 7700 – Structural Design Patterns3C«not exposed»myCMethod() Façade«exposed»cMethodOfFacade()Client12Adapted from Software Design: From Programming to Architecture by Eric J. Braude (Wiley 2003), with permission.Facade Design Pattern StructureCOMP 7700 – Structural Design Patterns4Sequence Diagram for Façade:ClientcMethodOfFacade()singleton:Facade:CmyCMethod()(return if any)(return if any)Adapted from Software Design: From Programming to Architecture by Eric J. Braude (Wiley 2003), with permission.COMP 7700 – Structural Design Patterns5Using Façade for Architecture of a Video GameMyGameCharactersMyGameEngineMyGameCast«facade»MyGame«facade»MyGameEnvironmentMyGameEnvironment«facade»Adapted from Software Design: From Programming to Architecture by Eric J. Braude (Wiley 2003), with permission.COMP 7700 – Structural Design Patterns6Design Goals At Work: Correctness and Reusability Collecting customer-related classes in a package with aclear interface clarifies the design, allows independentverification, and makes this part reusable.Adapted from Software Design: From Programming to Architecture by Eric J. Braude (Wiley 2003), with permission.COMP 7700 – Structural Design Patterns7UsingFaçade toAccessBankCustomersbankCustomersClientmain() «facade»BankCustomersdoDeposit( int amt, Customer cust, Account acc )getBankAccount( Customer cust, int accNum )getBankCustomer( String custName )introduceApplication()BankCustomer BankAccountCustomergetCustomerName()getNumAccounts()getPersonalNote()getAccount( int )AccountgetAccountNum()deposit( int )getBalance()1..nIntroMessageframeworkAccountExceptionCustomerExceptionAdapted from Software Design: From Programming to Architecture by Eric J. Braude (Wiley 2003), with permission.COMP 7700 – Structural Design Patterns8Output ofFaçade BankingExampleAdapted from Software Design: From Programming to Architecture by Eric J. Braude (Wiley 2003), with permission.COMP 7700 – Structural Design Patterns9Key Concept:  Facade Design Pattern -- modularizes designs by hiding complexityAdapted from Software Design: From Programming to Architecture by Eric J. Braude (Wiley 2003), with permission.COMP 7700 – Structural Design Patterns10Design PurposeAdd responsibilities to an object at runtime.Design Pattern SummaryProvide for a linked list of objects,each encapsulating responsibility.DecoratorAdapted from Software Design: From Programming to Architecture by Eric J. Braude (Wiley 2003), with permission.COMP 7700 – Structural Design Patterns11Decorator Class Model ClientobjDecoratedDecorationdoAction()1SubstancedoAction()Componentadd( Component )doAction()void doAction(){ ….. // do actions special to this decoration objDecorated.doAction(); // pass along} Adapted from Software Design: From Programming to Architecture by Eric J. Braude (Wiley 2003), with permission.COMP 7700 – Structural Design Patterns12LinkedObjects inDecoratordecoration1:Decorationdecoration1.objectDecorated:Decoration… :Decoration….:Substanceclient:ClientAdapted from Software Design: From Programming to Architecture by Eric J. Braude (Wiley 2003), with permission.COMP 7700 – Structural Design Patterns13Sequence Diagram for Decorator:ClientdoAction()decoration1:DecorationdoAction()Decoration1.objDecorated:Decoration:SubstancedoAction()Adapted from Software Design: From Programming to Architecture by Eric J. Braude (Wiley 2003), with permission.COMP 7700 – Structural Design Patterns14Output ofCustomer/AccountExampleCOMP 7700 – Structural Design Patterns15Process Phases Discussed in This ChapterRequirementsAnalysisDesignImplementationArchitectureFramework Detailed DesignxKey: = secondary emphasisx = main emphasisAdapted from Software Design: From Programming to Architecture by Eric J. Braude (Wiley 2003), with permission.COMP 7700 – Structural Design Patterns16Decorator Appliedto Customer /Accounts ExampleClientnextComponentAccountdescribe()1Customerdescribe()BankingComponentadd( Component )describe()CheckAccountdescribe()getLastCheckNum(): intSavingsAccountdescribe()getInterestRate(): intCDAccountdescribe()getDuration(): intSetupAttemptToAddBadBankingComponentExceptionCOMP 7700 – Structural Design Patterns17Use of Decorator in java.ioInputStreamReaderInputStreamBufferedReaderReader1Adapted from Software Design: From Programming to Architecture by Eric J. Braude (Wiley 2003), with permission.COMP 7700 – Structural Design Patterns18java.io Decorator example:InputStreamReaderSystem.in:InputStream: BufferedStreamReader Adapted from Software Design: From Programming to Architecture by Eric J. Braude (Wiley 2003), with permission.COMP 7700 – Structural Design Patterns19Key Concept:  Decorator Design Pattern -- allows addition to andremoval from objects at runtimeAdapted from Software Design: From Programming to Architecture by Eric J. Braude (Wiley 2003), with permission.COMP 7700 – Structural Design Patterns20Design PurposeRepresent a Tree of ObjectsDesign Pattern SummaryUse a Recursive Form in which thetree class aggregates and inheritsfrom the base class for the objects.CompositeAdapted from Software Design: From Programming to Architecture by Eric J. Braude (Wiley 2003), with permission.COMP 7700 – Structural Design Patterns21NonLeafNodeBasis for Composite Class ModelComponent“every object involvedis a Component object”“non-leaf nodeshave one or morecomponents”leaf nodenon-leaf nodeObjectsClasses1..nAdapted from Software Design: From Programming to Architecture by Eric J. Braude (Wiley 2003), with permission.COMP 7700 – Structural Design Patterns22NonLeafNodedoIt()Composite Class Modeletc.componentComponentadd( Component )doIt()LeafNodedoIt()TypeANonLeafNodedoIt()TypeBNonLeafNodedoIt()1..nClientFOR ALL elements e in component e.doIt()COMP 7700 – Structural Design Patterns23:LeafNodenonLeaf1ChildX:NonLeafNodenonLeaf1ChildX:NonLeafNodeSequence Diagram for