BTS430 Systems Analysis and Design using UML 3- tier architecture in Object-Level sequence diagrams

Three Tier Architecture Presentation Layer (UI classes) Business Logic Layer (data classes holding business logic) Persistent Data Layer (databases, DBMS, data access classes)

Three Tier Architecture Presentation Layer (UI classes) Business Logic Layer (data classes holding business logic) Persistent Data Layer (databases, DBMS, data access classes)

Three Tier Architecture Presentation Layer (UI classes) controller Business Logic Layer (data classes holding business logic) façade Persistent Data Layer (databases, DBMS, data access classes)

Controller/Façade Controller Façade Logic control for a component of a system Does not “do” much; passes messages to the appropriate objects Façade A specialized controller Acts as an interface into a subsystem (simplifies interaction with the subsystem)

Controller/Façade Controller Façade In BTS430 we will use a controller for all interaction between the UI and the business logic One controller per USE CASE Typically named handler or controller e.g. ManageCustomerHandler OR ManageCustomerController Façade In BTS430 we will use a façade as an entry point into the persistent data layer from the business layer

Controller/Façade Protects logic layer from variations in the presentation layer and the data layer UI, DBMS, DB changes, and so on Promotes “cohesion” within each layer Promotes “low coupling” between layers Promotes reuse Directs messages to the appropriate objects

Three Tier Architecture UI Business Logic Persistent Data