1. Structuring Adaptive Applications using AspectJ and AOM
Ayla Dantas and Paulo Borba
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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
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3. Centro de Informática - UFPE
Problems…
Adaptability may involve many system elements…
… and several aspects
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4. Centro de Informática - UFPE
Dictionary Example
Basic Functionalities
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5. Adaptability use cases
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6. Code scattering and tangling…
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7. Centro de Informática - UFPE
How?
How can we structure adaptive applications separating concerns and with a high degree of flexibility?
Using AOP and AOM
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8. Centro de Informática - UFPE
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)
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9. 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;
Advice
Inter-type declarations
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10. Adaptive behavior with AspectJ
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11. Customizing using Aspects
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12. And for the dynamic adaptations…
Use Adaptive Object Models
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13. Centro de Informática - UFPE
AOM Use
Application Metadata
Application behavior or characteristic represented as instances of EntityTypes, Entities, PropertyTypes, Properties and StrategyObject
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14. Providing Dynamic Adaptability
Obtain AOM information, interpret it into application new behavior and change the application using Aspects
Prepare metadata (e.g. XML)
representing dynamic application behavior
Make this information available
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15. AdapPE Pattern Overview
Core Application functionalities
Crosscut the application changing its behavior
Monitors the context
Adaptability implementation to be plugged to the application
Provides data for dynamic adaptations
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16. AdapPE Dynamics: Scenario I
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17. Centro de Informática - UFPE
Scenario II
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18. AdapPE Example: J2ME Dictionary
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19. Centro de Informática - UFPE
Adaptability Aspects
Customization
Screens
Internationalization
Resources Monitoring
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20. Interaction Between Pattern Elements
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21. 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
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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)
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23. Centro de Informática - UFPE
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
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24. Centro de Informática - UFPE
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
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25. Structuring Adaptive Applications using AspectJ and AOM
Ayla Dantas and Paulo Borba
{add,
Centro de Informática - UFPE