Lecture 01Enterprise Application Architecture

Agenda The Post-PC era Enterprise Application Building Blocks Service Oriented Architecture Layering

Reading Fowler Introduction,1 Layering Service Oriented Architecture Software as a Service Steve Yegge’s Rant

The Post-PC era

1960 1970 1980 1990 2000 2010

Mainframes

Mini computers

Personal Computers

Servers

Clusters

Cloud – utility computing

Laptops

Music player2G Cell phones

CONVERGE

DIVERGESmartphones

Tablets

Smart TV

Internet of things

2000 2010

THE DIGITALDECADE

“[The Personal Computer] can become the 'Digital Hub'

of our emerging digital lifestyle, adding tremendous value

to our other devices.”- Steve Jobs, 2001 Keynote

introducing the iPod

THE DIGITALDECADE

2000 2010

THE DIGITAL DECADE

MUSIC

PICTURES

VOICESMARTPHONES

TV SHOWS

MOVIES

BOOKS

WHAT HAPPENEDAT THE END OF THEDIGITAL DECADE?

1981-2011 The era of the PC

THE PC IS JUST ADEVICE

2000 2010

iMac iPhoneMac OS 9.0.4500 MHz PowerPC G3 CPU, 128MB MemoryScreen - 786K pixelsStorage - 30GB Hard Drive

iOS 4.01 Ghz ARM A4 CPU, 512MB MemoryScreen - 614K pixelsStorage - 32GB Flash Drive

Source: Ars Technical Images: Apple

Digital LifestyleThe “mobile web” is just the web – there is only one web

d ig i ta l on l ine wor ld

Digital Online World

WorkMore

informationFocused

Digital Online World

BrowsingConsuming

content

CheckingMobileNow

ConsumingVideo

Information

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) 1998-2008Digibarn Computer Museum,

Source: Picture from Convergence Transforms Digital Home: Techno-Economic Impact

The Post-PC Era New Requirements– More users, more complicated software– Uptime, security and reliability– Scalability– Competition drives need for productivity– Leveraging investments – integration with

existing systems

Challenges in Computing

Software and integration of components and devices are the challenges ahead

Cloud computing and ubiquity Move to Service Oriented Architecture and APIs

1980 1990 2000

HardwareConnecting hardware

NetworkSoftware

Connectingsoftware

New Approch to SoftwareArchitecture

Which of the following statements is not true?

A) The challenge ahead is to connect softwareB) The PC is no longer a device for developmentC) Computing has moved to the cloudD) During the digital decade, the PC was the digital hub for all you devices

QUIZ

✔

Enterprise Application

Enterprise Applications Software running in corporate data centers Characteristics– Involve data, some times huge amounts– Concurrent data access, multiple users– Lot of user interface screens– Integration with other enterprise application– Use of middleware software, such as

databases, application servers, web servers– Operated by specialists – system operators

Examples B2C (business to consumer)– E-commerce web sites such as Amazon, eBay– Commercial services like banking

Commerce Solutions– Payroll, patient records, shipping tracking, cost

analysis, credit scoring, insurance, supply chain, accounting, customer service, and foreign exchange trading

Information– Stock quotes, sports results, email, blogs

Software as a Service (SaaS) “On-demand” software– Cloud computing

IT infrastructure demands– Communication: interacting with the software– Scalability: dealing with fluctuation– Dependability: available 24/7

Software as a Service Examples E-mail services Project management Blog services

What is not necessarily characteristic of enterprise software?

A) Has many concurrent users working on the same dataB) Integrates with other IT systemsC) Deploys some form of distribution strategyD) Is operated by specialists not by the users

QUIZ

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Building Blocks

Building Enterprise Applications Building computer systems is hard– As the complexity of the

system gets greater, thetask of building thesoftware gets exponentially harder

Building Enterprise Applications Building computer systems is hard

DesignPattern

Middleware

FrameworksOOProgramming

SoftwareArchitecture

Software Architecture Shared understanding of system’s design

by the expert developers on a project– Highest-level breakdown of a system into its

parts– Decisions that are hard to change

Architecture influences design of components, technology, performance and middleware

There are always options

Object Oriented Programming OO is key to development of systems– Design for reusability, flexibility and

performance

One of the biggest hurdles for developers– Each component should be simple with simple

task– Involves understanding of interaction of parts

“OO design is more important than specific technologies, such as J2EE. We should try to avoid letting our technology choices, such as J2EE, constrain our ability to use true OO design” – Rod Johnson “If the design is good, there is no code”

– Jónas Þór, Senior Betware developer

Design Patterns Design using known ideas– Design patterns are standard solutions to

common problems in software design– Systematic approach for problems that

reoccur in software development– Patterns have name and definitions - not

language dependant History– Landmark book from 1995: Design Patterns:

Elements of Reusable Object-Oriented Software Gang of Four (GoF)

Middleware Enterprise system are built on middleware

– Can cover a broad spectrum of software and generally sits between an application and an operating system

– For example, databases, application servers, web servers, messaging systems, transaction monitors

– “The plumbing” Horizontal market

– Solves common problems – not specific business requirements

– Low-level system

Frameworks Frameworks define the support structure for how

to organize and build systems– Can improve productivity– We can use existing frameworks or build our own

Frameworks implement common problems– Developers extend and add their business requirements

Framework design– Use inheritance, inversion of control, interfaces and

helper classes– Implement design patterns

Which of the following statement is not true?

A) Design patterns are solutions to common problemsB) Object oriented programing is good for general problemsC) Frameworks are used to increase productivityD) Middleware can solve business related problems

QUIZ

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Evolution of Enterprise Software

Evolution60 70 80 90 00

IBMMainframes

Limitedlayering orabstraction

IBM, DECMini-

computersUnix, VAX

“Dumb”terminals

Screens/DB

PC, Intel,DOS, Mac,

Unix, Windows

Client/ServerDB

WindowsInternet

HTTP

Web Browsers

WebApplications

DB

Windows,Linux

MacOS

Browsers,ServicesDomain

ApplicationsDB

Evolution60 70 80 90 00

IBMMainframes

Limitedlayering orabstraction

IBM, DECMini-

computersUnix, VAX

“Dumb”terminals

Screens/DB

PC, Intel,DOS, Mac,

Unix, Windows

Client/ServerDB

WindowsInternet

HTTP

Web Browsers

WebApplications

DB

Windows,Linux

MacOS

Browsers,ServicesDomain

ApplicationsDB

iOSAndroidHTML5

BrowsersAppsAPI

CloudNoSQL

10

Client-Server Two-layer systems– Thick client on PCs handle user interface and

connect to servers for data

Client-Server The client handles all computation –

domain logic (business logic)– Limited reusability– Versioning is a challenge

Move to Three Tiers Three Layers– Presentation Layer for the User Interface– Domain Layer for the domain logic– Data Source Layer for the data access

Enter the Web Layer The Web added new challenges

– The browser accesses strings of tags (HTML)– Move the logic from client to a web layer

– Web layer adds connectivity by HTTP protocols

Application Servers Domain Components are deployed on

Application Servers– Distributed Multi-tiered Applications– Example:

• Web Servers, Spring, EJB containers

Client Types Native Applications – Apps – Usually use some OS GUI and APIs– Windows, Linux, MacOS, iOS, Andriod– Communication can be anything

Embedded– Run inside Web Browsers– Flash, Java Applets– Communication with XML using HTTP

Client Types Rich Internet Application (RIA)– JavaScript calls REST/SOAP services for data– HTML with XML/Json using Ajax/jQuery

HTML Presentation in Browsers– All functionality is server side– Simple HTML

Tiers vs. Layers Tier implies physical layer

– Example:• Client-server is two-tier system: client on one machine,

server on another

Layers do not need to run on separate machines– Layers can be on the same machine– Example:

• Web system with Web Layer, Domain Layer and Data Source Layer on the same machine, then the database on a separate machine

N-tier Web App Architecture Classic architecture

Which of the following statements is not true?

A) Versioning is only a challenge with client-service modelB) Layers need not be on a separate machinesC) Web servers can be used as application serversD) Scalability is achieved by duplicating the system

QUIZ

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Service Oriented Architecture

Imagine you are building an e-commerce web site

Traditional Architecture

Bookstore UI

Accounting service

Payment service

Shipping service SQLBrowser Apache

Benefits– Simple to develop and test, good architecture– One release and deployment– Easy to scale

Monolithic Architecture– Silo– Any subsystem can call other subsystems

Traditional Architecture

Drawbacks with the Monolith– UI requirements, multiple devices, streaming

real-time– Need to deploy everything to change one

component– Increased risk of failure– Fear of change– Updates are less often (A/B tests are difficult)

Traditional Architecture

Service Oriented Architecture Software Architecture where all

components are designed to be services Applications composed of interoperable

services– Easy to build new services– Easy to change

SOA Architecture

Bookstore Service

Accountservice

Payment service

Shipping service

Bookstore UI

API

Bezos’ Mandate1. All teams will henceforth expose their

data and functionality through service interfaces

2. Teams must communicate with each other through these interfaces

3. There will be no other form of interprocess communication allowed

Bezos’ Mandate4. It doesn't matter what technology they

use5. All service interfaces, without exception,

must be designed from the ground up to be externalizable. No exceptions.

6. Anyone who doesn't do this will be fired.

Which statement is not true about SOA?

A) SOA does not affect performanceB) No service can access other service data except using APIsC) SOA improves productivity though reuseD) Monoliths system must deploy all components

QUIZ

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Layering

Layering Software systems can get complicated– Abstractions are needed

Layering provides abstraction by separating computer systems in layers– Higher layers use services from

lower layers– Each layer has dedicated tasks

and hides complexity from upperlayers

Benefits of Layering You can understand a single layer as a

coherent whole without knowing much about other layers

You can substitute layers with alternative implementation of the same basic service

You minimize dependencies between layers Layers make good places for standardization Once you have a layer built, you can use it for

many higher-level services

Downsides Layers encapsulate some, but not all,

things well– Cascading changes– For example adding a field in the UI requires

changes on each layer Extra layers can harm performance– At every layer things typically need to be

transformed from one presentation to another

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”– Tends to creep into presentation and data source

Data Source– Connection to the database– Also Persistence

Summary The Post-PC era poses new challenges Enterprise Application defined Building Blocks for building enterprise

applications Service Oriented Architecture Layering is the oldest trick in the book