This document provides a summary and conclusions from a lecture on enterprise application architecture. It discusses that building complex computer systems gets exponentially harder with increased complexity. However, with proper techniques like layering, interfaces, object-oriented programming, design patterns, and frameworks, building large multi-tier systems can be done incrementally. It emphasizes separating concerns, minimizing dependencies between layers, and avoiding unnecessary complexity. Practical considerations include avoiding overdesign, overconfiguration, and not being constrained by frameworks. The future of enterprise software will involve challenges of connectivity between an increasing number of devices and software integration through APIs, cloud computing, and mobility.
2. “Advice is a dangerous gift”
There are no right answers
Use the advice to prod your
thinking, but don’t use it as a
replacement for your thinking
And remember, architecture is not
cast in stone
3. Building Enterprise Applications
Building computer systems is hard
– As the complexity of the
system gets greater, the
task of building the
software gets
exponentially harder
4. Building Enterprise Applications
Building computer systems is hard
Software
Architecture
Design
Pattern
OO
Programming
Middleware
Frameworks
6. Goals of an Enterprise Architecture
Be robust
Be performing and scalable
Take advantage of OO design principles
Avoid unnecessary complexity
Be maintainable and extensible
Be easy to test
7. Enterprise Systems
Building large multi-tier systems is done one line
at a time
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–
–
–
–
–
–
–
Layering
Clear interfaces
Minimize dependencies
Separation of concerns
Object Oriented programming
Design patterns
Frameworks
Testable code
8. Create Abstractions
Minimize dependence on subsystems
– Must be easy to change
• Gateway, Mapper, Service Stub
Abstract things that varies from what stays the
same
– Design principles
• Factory, Plugin, Dependency Injections
9. Separation of Concerns
One of the main challenge of frameworks is to
provide separation of concerns
Frameworks deal with generic functionality
Frameworks need patterns to combine generic and
domain specific functionality
10. Minimize dependencies
Be careful with dependencies
– It is easy to create code where modules depend on
other modules
• Plugin, Factory, Service Layer, Separated Interface,
Dependency Injection and Observer Pattern
11. Layering
Software systems can get complicated
– Abstractions are needed
Provides abstraction by separating computer
systems in layers
– Higher layers use services from
lower layers
– Each layer has dedicated task
and hides complexity from upper
layers
12. The Three Layers
Presentation
– User’s interface to the system
– User can be another system
– Accepts input, displays views
Domain
– The Application of the system
– The “Business logic”
– Has the tendency to creep into other layers
Data Source
– Connection to the database
13. Three Layers
Presentation Layer for the User Interface
Domain Layer for the domain logic
Persistence Layer for the data access
14. Considerations
Don’t overdesign!
– User Interfaces are really difficult to make generic and
reusable
– If there is no need for extra layer, don’t have it
– If you don’t need an interface, don’t have it
Don’t let frameworks rule you!
– If you have to write code just to satisfy a framework,
maybe there is another way – or fix the framework
– Frameworks can overdo it
15. Considerations
Don’t overdo Configurations
– Sometimes coding is better than config
– Testing and debugging config is hard
Don’t be afraid to Refactor
– You can always add another indirection
– You can always add a new layer
Design Principles are good guidelines
– Don’t be afraid to reevaluate them
18. Practical Considerations
Agile is an answer to this
Daily
Standup
Sprint
stories
Backlog
Backlog
ordered by
Product Owner
Working
Product
1-2 week
sprints
Working
Product
Released
33. The Post-PC Era
The Personal Computer era is over
– Rise of the network
– APIs
– Enterprise systems are accessible
by consumers
– New devices, mobile phone,
ITV, game machines, MP3 players,...
Source: (cc) 1998-2008
Digibarn Computer Museum,
Source: Picture from Convergence Transforms Digital Home: Techno-Economic
Impact
34. Challenges in Computing
Hardware
1980
Connecting hardware
Network
1990
Software
Connecting
software
2000
Software and integration of components and
devices are the challenges ahead
Cloud computing and ubiquity
Move to Service Oriented Architecture and APIs
37. Objectives
Know the basics of software design and
beautiful code
Understand and know how to use design
patterns
Implement software framework with component
reuse in mind
38. Objectives continued
Understand different software architectures and
the different design choices
Understand Software Oriented Architecture
(SOA) and Software as a Service (SaaS)
Understand the practices of how professional
software is developed in the software industry