Editor’s Choice -AOP and IoC

AOP : New Programming Design Paradigm
Aspect Oriented programming (AOP) decomposes a system into concerns (i.e. term referring to the core elements required to focus on), instead of objects. It deals with “aspects” that cross-cuts across the code which could be difficult or impossible to modularize with OOP

Seperation of concerns (SoC)
AOP promotes separation of concerns within the systems where separation of concerns (SoC) is a process to break a computer program into distinct features that were previously overlapping in functionality, as little as possible. A concern is any piece of interest needed to focus on while developing a program. Typically, concerns are synonymous with features or behaviors, lets talk of a credit card processing system, the related core concern of the system deals with processing the monetary transactions, while its application-level concerns handles logging, transaction integrity, authentication, security, performance, and so on. Many such concerns are known as crosscutting concerns. Lets talk of Logging, it offers one example of a crosscutting concern. A logging strategy necessarily affects every single logged part of the system. Logging thereby crosscuts all the logged classes and methods.

Such crosscutting concerns affect the multiple implementation modules. With the current programming methodologies, crosscutting concerns span over multiple modules causing a system to be complex to design, understand, implement, evolve and even maintain with time.

Lets quickly give a glance to the OOPs concept. OOPs programming model creates programs around the real world entities. Here the programs are developed around the objects and data rather than actions and logics. In OOPs, every real life object has properties and behavior. This feature is achievable with different languages like C++, Java, C# etc. However in the current scenario, object-oriented programming (OOP) seems to be no more an extra-ordinary programming model where real world problems are decomposed into objects


encapsulating behavior and data in a single unit. Although the developers have met great success in the past in modeling and implementing complex software systems, However they faces crucial problems in maintaining the code while working with large projects. Most of the time, to make a minor change to a program may require maintaining several updates to a large number of unrelated modules. Now with the advent of AOP, such problems are easily rectified, as it allows the developers to solve the complex problems involved with software development that couldn’t be resolved easily with the object-oriented programming techniques.

However, AOP being a new programming technique, allows programmers to modularize crosscutting concerns. It allows the programmers to dynamically modify the static OO model to create a system that cangrow to meet new requirements. It allows separating the crosscutting concerns into the single units called aspects.

It is a modular unit of crosscutting implementation, which encapsulates behaviors that affect multiple classes into reusable modules. AOP is not bound to a specific programming language. It is a concept that can be implemented with different languages (for example C++, Smalltalk, Java etc.). 

Aspect-Oriented Software Development (AOSD) Aspect-Oriented Software Development (AOSD) attempts to aid programmers in the separation of concerns, specifically cross-cutting concerns, as an advance to the modularization. AOP does so using primarily language changes, while AOSD uses a combination of language, environment, and method. 

The core construct of AOP is the aspect, which
encapsulates behaviors affecting multiple classes
into reusable modules. Systems are composed
of several components each responsible for a
specific piece of functionality. Irrespective of the
core functionality of a program, the system
services like logging, transaction management,
security etc., must be included in the program.
These system services are commonly referred
to as ‘cross-cutting concerns’ as they tend to

Nov 2007 | Java Jazz Up | 5
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