By Bob Bunson rbunson@munichreamerica.com. Simulation of software development project Fictitious system from Concept to Code Oriented around the.
Post on 24-Dec-2015
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Pragmatic Architecture
By Bob Bunsonrbunson@munichreamerica.com
Software Architecture is…
The Approach
Simulation of software development project Fictitious system from Concept to Code Oriented around the software architect
The purpose of this exercise is to demonstrate: Architecture considerations Architecture activities The realization of architecture in code
Roles
My role Architect
Your candidate roles Architect reviewer Architect
apprentice Coder on future
iterations Passive observer
What I* mean by Architecture
The critical decisions that define a system
The decisions that are hard to change
*By “I”, I really mean the actual thought leaders in the industry
Tax Calculator - Business Requirements
Produce a free tax calculator so that people can compute their taxes, plus their late penalties, so that they can pay the IRS
Tax Calculator - Non-Functional Requirements
Design for testability Run on all modern browsers Maintainability Productivity should
not decrease as the application grows
All errors logged High performance All pages should
display in .6 seconds Simple enough to demonstrate
Brush up on Architecture
Tax Calculator - Architecture Principles
Interesting, but small No technology distractions Interoperability
Tax Calculator - An Expanded Principle
No Technology Distractions Statement
During a presentation on basic application architecture, the introduction of new or trendy technologies should be avoided
Rationale New, trendy, or controversial technologies has the
potential to distract the audience and potentially impede the presenter from communicating about the foundations of architecture
Implications Increased focus on the primary topic Lost opportunity to learn a new technology in preparing
for the presentation
Tax Calculator - Architecture Constraints
All ETL must use SQL Server Integration Services
.NET platform Coding based on Microsoft naming
conventions and “Clean Code” guidelines
Tax Calculator - Risk Assessment
Congress will change the tax laws retroactively prior to the presentation
Internet could be unreliable during this presentation
Web Forms and Test Driven Development don’t work well together
Risk Management Principles
Open communication
Integrated with the audience
Tax Calculator - Risk Management Strategy
“Web Forms and TDD causes too much friction” Microsoft created
ASP.NET MVC for a reason
To mitigate, create a prototype to evaluate the ease and intuitiveness (avoid the need to be clever and creative) of writing tests and code
Tax Calculator - Prototyping Goals
Explore variations of the model-view-presenter pattern (Supervising Controller, Passive View)
Introduce a few anticipated scenarios such as working with Session State
Prototyping
Why Mitigate risk Communicate concepts Understand technology
What Throw away Evolutionary
Architecture Patterns
Web Presentation Patterns Model View Controller Model View Presenter Page Controller
Domain Logic Patterns Transaction Script Domain Model Table Module
Tax Calculator – Architecture Tradeoffs
“Design for Testability” vs. “No Technical Distractions” ASP.NET MVC better for testability But would violate principle of “No
Technical Distractions” “Performance” vs. “Simple Enough to
Demonstrate” vs. Usability AJAX would improve performance and user
experience, but would Add to the complexity of the system
Tax Calculator – Technology Selections
ASP.NET Web Forms Nunit Visual Studio Web Server Windows Vista WatiN for Acceptance Testing
Tax Calculator – Key Design Decisions and Justifications
Use of ASP.NET Web Forms over ASP.NET MVC Supports principle of “No Technology
Distractions” Use of NUnit over MSTest
Would get kicked out of Alt.Net if I used MSTest Domain Model over Dataset
Preference of a domain model which encapsulates behavior and data to support potentially complex tax calculations over DataSets
More easily testable
Tax Calculator – More Key Design Decisions
Model View Presenter Desire to keep behavior out of code-
behind to support principle of Testability Introduce Rhino.Igloo open source
tool to abstract HTTP Context for easier testing Prototyping uncovered obstacles
associated with creating unit tests without dependencies on Session, Request, Response, etc.
Modeling with UML
Why Model
Martin Fowler: UML as Sketch UML as Blueprint UML as a
Programming Language
Reverse Engineering Forward Engineering
Tax Calculator – Class Diagram
No Best Practices
Context Tradeoffs, constraints, and the real world
exist Effective architecture
Factors in context Applies patterns when they apply Leverages experience (own and others)
There is no ideal best architecture
Tax Calculator – Aspects of Code Discussion
Realization of the software architecture in code
Testability of the layers Object oriented principles in practice Few thorny topics Prioritized until we run out of time Give “architect reviewers”
something to do when the code falls short in any area
Tax Calculator – Code Preview
Testing▪ Readable, descriptive tests▪ Arrange, Act, Assert▪ Test Doubles – visualize where a mocking
framework might help▪ Differentiate between unit tests and
acceptance tests
Tax Calculator – Code Preview Application
Dependency Injection - visualize where an Inversion of Control container might help
Model View Presenter Domain model Validation Error Handling Layer super types Testable code
Tax Calculator – Code Preview
UI can also support architecture principles Separation of Concerns: HTML and CSS Maintainability: Master page, Layer
super type Interoperability: XHTML User Experience: At least the potential of
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