Structuring Adaptive Applications using AspectJ and AOM

Structuring Adaptive Applications using

AspectJ and AOM

Ayla Dantas and Paulo Borba{add, phmb}@cin.ufpe.br

Centro de Informática - UFPE

Centro de Informática - UFPE 2

Motivation“A program is called adaptive if it

changes its behavior automatically according to its context.” WAAS’95

“The shift toward ubiquitous computing poses multiple novel technical, social, and organizational challenges, which

include analyzing new families of nonfunctional requirements (such as

configurability and adaptability).” CACM Dec 02


Problems…Adaptability may involve many system Adaptability may involve many system elements…elements…

… … and several aspectsand several aspects


Dictionary ExampleBasic FunctionalitiesBasic Functionalities


Adaptability use cases


Code scattering and tangling

…


How?How can we How can we

structure adaptive structure adaptive applications applications

separating concerns separating concerns and with a high and with a high

degree of flexibility? degree of flexibility?

Using AOP and AOM


Using AOP AOP is a technology intended to provide clear

separation of concerns Particular execution points (join points) can be

identified using AOP Actions can be taken at those points, and may be

defined in a modular unit of crosscutting implementation (aspect)


AspectJ Language

pointcut showingScreen(): execution (public void showScreen(byte)) ;

before(): showingScreen(){ System.out.println( "A screen will be shown");

}

public static final byte A. REGISTRATION_SCREEN=-3;

Pointcut

Advice

Inter-type declarations


Adaptive behavior with AspectJ


Customizing using Aspects


And for the dynamic adaptations…Use Adaptive Object ModelsUse Adaptive Object Models


AOM Use

Application Metadata

Application behavior or characteristic represented as instances of EntityTypes,

Entities, PropertyTypes, Properties and StrategyObject


Providing Dynamic Adaptability

Prepare metadata (e.g. XML)

representing dynamic

application behavior

Make this information

available

Obtain AOM information,

interpret it into application new

behavior and change the

application using Aspects


AdapPE Pattern OverviewCore

Application functionalitie

s

Monitors the

context

Provides data for dynamic

adaptations

Crosscut the

application changing

its behavior

Adaptability implementation to be plugged

to the application


AdapPE Dynamics: Scenario I


Scenario II


AdapPE Example: J2ME J2ME DictionaryDictionary


Adaptability Aspects

Customization Screens Internationalization Resources Monitoring


Interaction Between Pattern Elements


And what about AOM and patterns? Most AspectJ actions can be replaced by the

Decorator(Wrapper) or the Adapter patterns Sometimes, a lot of refactoring is necessary in

order to compose concerns A pure OO solution can lead to redudancy if we

want flexibility As the number of adaptive concerns increase, in

order to combine concerns, the system complexity will increase

The code size (LOC) is bigger than for an AspectJ solution


However…

The use of AOP requires learning a new language, but in the case of AspectJ, just some new constructions as it is an extension for Java.

In our experiment, the solution using aspects generates an executable file which is 16% bigger than a pure OO solution using GoF patterns.

The execution time is sometimes bigger too (12.53% for the most used method)


Conclusions We have good modularization with AspectJ Pure OO solutions generally require more

changes, and can lead to complex systems AspectJ increases the bytecode size, but it is

an acceptable increase Flexibility x Code Size The use of auxiliary classes is important


Conclusions

The necessity of refactoring still exists Aspects reuse can be explored AOM helps in providing dynamic adaptations J2ME and AspectJ Applicability for other platforms

Structuring Adaptive Applications using

AspectJ and AOM

Ayla Dantas and Paulo Borba{add, phmb}@cin.ufpe.br

Centro de Informática - UFPE

Structuring Adaptive Applications using AspectJ and AOM

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