net architecture for enterprises
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.NET Architecturefor Enterprises
Wade WegnerArchitect, Microsoft Corporationwade.wegner@microsoft.comhttp://www.architectingwith.net/
First, a story …
First, a story …personal^
There once was a developer …
… who really enjoyed coding …
.NET
Python
JavaScript
HTML
Web Services
BizTalk
Tibco
SQL Server
OracleAS/400
Window Server
Apache
IIS
SOA
… and then one day …
… through no fault of his own …
… someone called him an architect.
How did this happen?
Was he suddenly adifferent person?
Did he now need to careabout different things?
Goals
Leave with a better understandingof architecture
Goals
Leave with a better understandingof architecture
Goals
software^
Understand the practical aspectsof architecture in .NET
Goals
What is architecture?
Why should I care?
How is software architecturedifferent?
Determining how to do something
Making expensive andhard-to-change decisions
Who is the architect?
Are there different typesof architects?
Are architects project managers?
Should architects write code?
Do architects just focuson abstractions?
Poor software typicallyhas one of two causes …
… insufficient skills.
… contradictory and ambiguousrequirements.
Anyone can write codethat just works.
Our goal should be …
… to write good codethat works.
Why?
For poorly written code“that just works”…
… maintenance is expensive
… maintenance is frustrating
… maintenance is time consuming
How do we write good codethat works?
Tenets of Structured Design
Cohesion
Tenets of Structured Design
Coupling
Tenets of Structured Design
Low coupling &High cohesion
Tenets of Structured Design
Separation of Concerns
Identifying the concerns
Separation of Concerns
Modularity
Separation of Concerns
Information hiding
Separation of Concerns
So, what are some principles that make this easier?
Find Pertinent Objects First
Principles
Find Pertinent Objects First
Principles
To view all orders placed by a customer, the user indicates the customer ID. The program displays an error message if the customer does not exist. If the customer exists, the program displays name, address, date of birth, and all outstanding orders. For each order, the program gets ID, date, and all order items.
Favor Low Coupling
Principles
Favor Low Coupling
Principles
Program to an interface, not an implementation
Favor Code Reuse
Principles
This is great, we know this …so, what else is there?
Open/Closed Principle
Advanced Principles
Liskov’s Substitution Principle
Advanced Principles
Dependency Inversion Principle
Advanced Principles
Dependency Inversion Principle
Advanced Principles
public class Foo{
IDoSomething _doSomething = null;
public Foo(IDoSomething doSomething){
_doSomething = doSomething;}
}
Patterns
Design Patterns
Patterns
Architectural Patterns
Patterns
Antipatterns
Patterns
Patterns are not …
… a verb
Patterns are not …
… superhuman
Patterns are not …
… inherently good nor evil
Patterns are not …
Testability & Security
Testability
Software Testing
Testability
Software Contracts
Testability
Unit Testing
Testability
Dealing with Dependencies
Testability
Fakes to Mocks
Testability
Security
Security as a requirement
Security
Security Development Lifecycle
Security
Layering
Security Development Lifecycle
Componentization
Security Development Lifecycle
Roles
Security Development Lifecycle
Threat models
Security
Okay, is this it?
Interesting, but abstract
How does this help me design my system?
Let’s look at the common layers of any system …
The Business Layer
The Service Layer
The Data Access Layer
The Presentation Layer
The Business Layer
What is it?
The Business Layer
Domain’s Object Model
The Business Layer
Domain Entities
The Business Layer
Business Rules
The Business Layer
Validation
The Business Layer
Business Process & Workflow
The Business Layer
Where do you deploy it?
The Business Layer
The Gray Areas
The Business Layer
Data Formatting
The Business Layer – Gray Areas
CRUD
The Business Layer – Gray Areas
Stored Procedures
The Business Layer – Gray Areas
Patterns
The Business Layer
The Transaction Script Pattern
The Business Layer
The Table Module Pattern
The Business Layer
The Active Record Pattern
The Business Layer
The Domain Model Pattern
The Business Layer
The Service Layer
What is it?
The Service Layer
What’s service orientation?
The Service Layer
What about SOA?
Service-Oriented Architecture
The Services Layer
Tenets of SOA
The Services Layer
Boundaries Are Explicit
Tenets of SOA
Services Are Autonomous
Tenets of SOA
Use Contracts, Not Classes
Tenets of SOA
Compatibility Is Based on Policy
Tenets of SOA
What SOA is not …
… a revolution
SOA is not …
… a technology
SOA is not …
… a web service
SOA is not …
… a goal
SOA is not …
The Data Access Layer
What is it?
The Data Access Layer
Requirements
The Data Access Layer
Database Independence
DAL: Requirements
Configurable as a Plug-in
DAL: Requirements
Persisting the Application’sObject Model
DAL: Requirements
Responsibilities
The Data Access Layer
CRUD services
DAL: Responsibilities
Query services
DAL: Responsibilities
Transactions
DAL: Responsibilities
Concurrency
DAL: Responsibilities
Separated Interface Pattern
The Data Access Layer
The Plugin Pattern
The Data Access Layer
Should you write your own DAL?
The Data Access Layer
O/RMs
The Data Access Layer
Entity Framework
EntitySpaces
NHibernate
Genome
LINQ-to-SQL
LLBLGen Pro
Using an O/RM Tool
The Data Access Layer
Stored Procedures?
The Data Access Layer
SPs are faster than SQL code
DAL: Stored Procedure Myth #1
SPs are more secure than SQL code
DAL: Stored Procedure Myth #2
SPs can be used to fend off SQL injection
DAL: Stored Procedure Myth #3
SPs can be used to reduce brittleness of SQL code
DAL: Stored Procedure Myth #4
Stop! What are you saying?
Do we still need DBAs?
The Presentation Layer
Responsibilities
The Presentation Layer
Validation?Formatting?
Styling?Usability?
PL: Responsibilities
Independence from graphics
PL: Responsibilities
Independence from UI Technology
PL: Responsibilities
Testability
PL: Responsibilities
Independence from data model
PL: Responsibilities
Patterns
The Presentation Layer
Model-View-Controller (MVC)
PL: Patterns
Model-View-Presenter (MVP)
PL: Patterns
How do I choose a pattern?
The Presentation Layer
Summary
Defined Architecture
Summary
Described Architects
Summary
Maintainability
Summary
Low coupling & high cohesion
Summary
Principles of software architecture
Summary
Design patterns
Summary
Architecture patterns & antipatterns
Summary
Testability & Security
Summary
The Business Layer
Summary
The Services Layer
Summary
The Data Access Layer
Summary
The Presentation Layer
Summary
Closing thoughts …
“It” depends
Closing thoughts …
Requirements
Closing thoughts …
Reuse is a nice side effect
Closing thoughts …
Separation of Concerns
Closing thoughts …
Maintainability
Closing thoughts …
Don’t trust your users
Closing thoughts …
Security and testability by design
Closing thoughts …
© 2009 Microsoft Corporation. All rights reserved. Microsoft, Windows, Windows Vista and other product names are or may be registered trademarks and/or trademarks in the U.S. and/or other countries.The information herein is for informational purposes only and represents the current view of Microsoft Corporation as of the date of this presentation. Because Microsoft must respond to changing market conditions, it should not be interpreted to be a commitment on the part of Microsoft, and Microsoft cannot guarantee the accuracy of any information provided after the date of this presentation. MICROSOFT MAKES NO WARRANTIES, EXPRESS,
IMPLIED OR STATUTORY, AS TO THE INFORMATION IN THIS PRESENTATION.
wade.wegner@microsoft.comhttp://architectingwith.net
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