Three Layer Architecture

Why Bother with the Middle Layer?

Consider Facebook

PC

Phone

Tablet

Without a Middle Layer…

Web browser(Add Update etc.)

Android device(Add Update etc.)

Apple device(Add Update etc.)

Presentation Layer Middle Layer Data Layer

Include the Middle Layer…

Web browser

Android device

Apple device

Presentation Layers

Middle Layer(Add

UpdateDelete

ValidateQuery Results)

Data Layer

Designing Classes

The SpecificationYou are required to create a web based

application that allows a user to store address details. The user should be able to add, edit and delete addresses. Each address should be validated to capture any errors in the data. A typical address should consist of house no, house name, street, town, post code, county code, date added and a flag for active. All addresses will be stored in a suitable database.

Identify the NounsApplicationAddressAddressesUserDataDatabase

List the MethodsAddEditDeleteValidate

Find the Propertieshouse nohouse namestreettownpost codecounty codedate added active

Draw the Class

Addresshouse no : stringhouse name : stringstreet : stringtown : stringpost code : stringcounty code : integerdate added : dateactive : BooleanAdd() : BooleanEdit() : BooleanDelete() : BooleanValidate() : String

Now we write the code…