Aspect-Oriented Software Development

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Aspect-Oriented Software

Development

Dr. Awais Rashid

Computing Department

Lancaster University, UK

© Awais Rashid, 2005.

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Fundamental to Next

Generation Software

•

“AOSD is vital to our [IBM Software Group’s]

survival”.

Daniel Sabbah, IBM Vice President, speaking at

AOSD Conference, Lancaster University, 2004.

•

AOSD among top ten most promising technologies.

MIT Technology Review

• Being employed in

projects at IBM, Siemens, Boeing,

BEA, Oracle and NASA.

•

DARPA

PCES Programme investing approx.

15 million

USD/year

•

Support of 4.4m Euros to AOSD-Europe by the EC

•

Will be at the Plateau of Productivity in 5-10 years

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Outline

• Motivation

• Aspect-Oriented Software

Development

• State-of-the-art in languages, methods

and tools

• Case studies

• Open issues

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Need to Tackle Complexity

• Software systems are becoming

increasingly complex

• Estimated 15 million software

professionals worldwide

• Estimated 8000 lines of code per

developer per year

⇒

36 billion lines of code per year

worldwide

• Do the above figures add up?

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Complexity Affects Quality

• Intrinsic vs extrinsic complexity

• Affects quality attributes of software

systems

• Evolvability

• Cost-efficiency

• Composability

• Reliability

• Fault tolerance

• Reusability

• Scalability

• Dependability

• Adaptability

• Etc.

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Need for Separation of

Concerns

Development requires focusing on one concern

at a time

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Outline

• Motivation

Development

and tools

• Case studies

• Open issues

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Aspect-Oriented Software

Development (AOSD)

Distribution Security Data Management

AOSD tools, techniques and methodology Distribution Security Data Management

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Potential Benefits of AOSD

• Improved ability to reason about problem

domain and corresponding solution

• Reduction in application code size,

development costs and maintenance time

• Improved code reuse

• Requirements, architecture and design-level

reuse

• Improved ability to engineer product lines

• Context-sensitive application adaptation

• Improved modelling methods

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History and Evolution of

AOSD

Evolution

Time

In the Making Initial

BreakthroughExcitement Stabilisation TowardsMaturity

Composition Filters, Adaptive Prog., SOP, Reflection AspectJ @ PARC Hyper/J, UML Ext. AspectJ @ Eclipse, AOSD Conf.

More expressive Langs., Early Aspects,

Middleware, Databases, Industrial Applications, Transactions on AOSD

“AOSD is vital to our [IBM Software Group’s] survival”.

Daniel Sabbah, IBM Vice President, speaking at

AOSD Conference, Lancaster University, 2004.

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Crosscutting: The Logging

Concern in a Bank Application

class Account { // some attributes

void deposit(int amount) { Logger.log(“Entering Account.deposit( )”); // method code Logger.log(“Leaving Account.deposit( )”); } String holderName( ) { Logger.log(“Entering Account.holderName( )”); // method code Logger.log(“Leaving Account.holderName( )”); // return a string } class Loan { // some attributes void sendReminder( ) { Logger.log(“Entering Loan.sendReminder( )”); // method code Logger.log(“Leaving Loan.sendReminder( )”); } int getBalance( ) { Logger.log(“Entering Loan.getBalance( )”); // method code Logger.log(“Leaving Loan.getBalance( )”); // return an integer }

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Tangling and Scattering

Account Loan Customer

Data Classes

ATM Web PC Terminal

User Interface

Persistence

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Revisiting the Logging Example

class Account { // some attributes

void deposit(int amount) { Logger.log(“Entering Account.deposit( )”); // method code Logger.log(“Leaving Account.deposit( )”); } String holderName( ) { Logger.log(“Entering Account.holderName( )”); // method code Logger.log(“Leaving Account.holderName( )”); // return a string } class Loan { // some attributes void sendReminder( ) { Logger.log(“Entering Loan.sendReminder( )”); // method code Logger.log(“Leaving Loan.sendReminder( )”); } int getBalance( ) { Logger.log(“Entering Loan.getBalance( )”); // method code Logger.log(“Leaving Loan.getBalance( )”); // return an integer }

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Wouldn’t it be Nice if …

class Account {

// some attributes

void deposit(int amount) { // method code } String holderName( ) { // method code // return a string } class Loan { // some attributes void sendReminder( ) { // method code } int getBalance( ) { // method code // return an integer } aspect Logger {

when someone calls these methods

before the call {Logger.log(“Entering ” + methodSignature);} after the call {Logger.log(“Leaving ” + methodSignature);} }

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Revisiting the Persistence and

Security Example

Data Classes

ATM Web PC Terminal

User Interface

Persistence

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Wouldn’t it be Nice if …

Data Classes

ATM Web PC Terminal

User Interface

aspect Persistence

aspect Security

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Aspect-Oriented

Programming (AOP)

Class A

Class B

Classes

Aspects

Aspect X Aspect Y

Aspect

Weaver

Composed

Code

Legend

Join Points: Reference points in classes used by aspects for specifying relationships with classes

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The Notion of a Join Point

class Account {

// some attributes

void deposit(int amount) { // method code } String holderName( ) { // method code // return a string } class Loan { // some attributes void sendReminder( ) { // method code } int getBalance( ) { // method code // return an integer } aspect Tracing {

when someone calls these methods

before the call {Logger.log(“Entering ” + methodSignature);} after the call {Logger.log(“Leaving ” + methodSignature);} }

Type

of

Join Point

Points in this

Specific Join

Program that

we are

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Programmer Productivity

(without AOP)

• Typically one class or component per

file

• For a typical release of a software

system, logging or tracing effort

– 15 minutes per file

• 100 files will require 25 person hours

• 1000 files will require 7 person weeks

Source: Adrian Colyer, Gregor Kiczales, Adoption of AOSD, AOSD Conference 2005

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Programmer Productivity (with

AOP)

• Typical effort to write a tracing or

logging aspect

– Less than 25 person hours for a simple

one

– Less than 50 person hours for a more

elaborate, properly tested aspect

– Write once, reuse again and again

– Very cost-effective

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Outline

• Motivation

Development

and tools

• Case studies

• Open issues

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Aspect-Oriented Programming

Languages and Frameworks

• AspectJ and AJDT (Eclipse) – IBM

• AspectWerkz and WebLogic – BEA

• JBoss AOP – JBoss Group

• Spring AOP – Spring project

• AspectS – DoCoMo Labs

• CaesarJ – Technical Univ. of Darmstadt

• AspectC – Univ. of British Columbia

• AspectC++ – Univ. of Erlangen-Nuremberg

• A number of other AOP languages, frameworks and

tools listed at: http://aosd.net

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Aspect-Oriented Requirements

Analysis and Design

• 15 million software professionals

worldwide

• Only 30% are coders

1

• A significant effort goes into:

– Requirements engineering

– Modelling

– Architecture and design

– Testing and evolution

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Better Understanding of the

Problem Domain

• Early Aspects: Aspect-oriented

requirements engineering

– Better understanding of the influence of

crosscutting properties on the problem

– Identify trade-offs early on

– Support decision making amongst stakeholders

– Early aspects drive architectural choices

• A number of UML extensions are already

available for subsequent modelling and

design

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Preserving Architectural

Constraints

• Use aspects to declare warnings or

errors on unwanted development

practices

• Example: IBM Software Group

– Aspects are used to flag warnings when

one product uses APIs from another

– Used in a portfolio of 30 products

– 50000 such places flagged!

– Facilitates packaging and deployment

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Outline

• Motivation

Development

and tools

• Case studies

• Open issues

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Enterprise Software: IBM

WebSphere

• Multiple crosscutting concerns

(without

AOSD)

Please refer to Dr. Daniel Sabbah’s keynote at AOSD conference at Lancaster in 2004:

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Enterprise Software: IBM

WebSphere

• First Failure Data Capture

(without AOSD)

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Enterprise Software: IBM

WebSphere

• First Failure Data Capture

(with AOSD)

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Database Evolution: Lancaster

Study

A: Attributes deleted from non-leaf class

B: Introduction of non-leaf class

C: Attributes deleted from leaf class D: Class repositioned 0 5 10 15 20 25 A B C D System X SADES 0 2 4 6 8 10 A B C System X SADES System Y A: Customising routines resulting from additive change

B: Customising routines resulting from

subtractive change

C: Changes to entities upon customisation of instance adaptation approach

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Database Aspects in Oracle

TopLink

• Aspects used for exception raising

whenever a developer attempts to write to

the database in a read-only profile

• Aspects used to mark objects as

dirty

for

database updates in a read-mostly profile

• Aspects at the vendor end only

• TopLink developers do not need to know

AOSD

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Design Pattern Implementations

• Design patterns are solution templates

for recurring problems during software

development

• Already help to modularise design and

code by guidelines for good structure

• AOSD can further improve the

implementation of several design

patterns

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Concern Diffusion over

Components

0 2 4 6 8 10 12

Component Decorator Mediator Colleague Handler Memento Originator

N u m b e r of C o m pone nt s Number of Components AO OO AO OO Decorator Pattern Mediator Pattern CoR Pattern Memento Pattern +67% +80% +50% 0% 0% +57% +40% _-20% +29% +25% -33%

Before After Before After Before After Before After Before After Before After Before After

+67%

0% +67%

system viewpoint

CDC

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Separation of Concerns

0 5 10 15 20 25 30 35

N u m b er of Tr a n s itio n Poin ts Num b er of Transition Points AO OO AO OO Mediator Pattern Memento Pattern +78% +25% +85% +22% 0% 0%

Before After Before After Before After Before After Before After Before After Before After +67% 0% +92% CoR Pattern +88% Decorator Pattern +50%+50% 0% +75% 50 CDLO C

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Scalability: Introducing New

Elements

0 2 4 6 8 10 12

Nu m b e r o f C o m p o n e n ts Number o f Co m p onen ts AO OO AO OO Decorator Pattern Mediator Pattern CoR Pattern Memento Pattern +67% +80% +50% 0% 0% +57% +40% _-20% +29% +25% -33%

Before After Before After Before After Before After Before After Before After Before After

+67% 0% +67% 0 5 10 15 20

Component Decorator Mediator Colleague Handler Memento Origin

N u m b er o f O p er at io n s Number o f O p er atio ns AO O AO O Decorator Pattern Mediator Pattern Memento Pattern +75% +88% +71% 0% 0% +67% -46% -+6% +60% -40%

Before After Before After Before After Before After Before After Before After Before +67% -14% -29% CoR Pattern 0 5 10 15 20 25 30 35

Component Decorator Mediator Colleagu

N u m b er of Tra n si ti o n P o in ts Number o f Tra n sition Points Mediator Pattern +78% +25%

Before After Before After Before After Before Af +67%

+88% Decorator Pattern

+50%+50% 0%

+75

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Other Interesting Projects

• Boeing: Autopilot software product lines

• Siemens: Software product lines and

model-driven development

• New Aspects of Software: Modularising

security policies

• Near Infinity: Auditing in Intelliprints

• TU Darmstadt and TU Berlin: ToppRax

project (evaluation in SMEs)

• Lancaster University: Infolab21 Knowledge

Business Centre (Planned seminars for

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Outline

• Motivation

Development

and tools

• Case studies

• Open issues

(38)

Open Issues for AOSD

• Need for more research into models for

early aspects: aspect-oriented requirements

engineering and architecture design

• Need for more research into aspect

mapping and traceability

• Need for effective testing and validation

techniques

• Need for more application studies

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Open Issues for AOSD

• Need for AOSD processes

– Adaptation of existing processes to

incorporate AOSD

• Need for more empirical studies

• Need for an

Aspect-Oriented Software

Engineering