Aspect-based programming

Aspect-oriented programming is a software development style that emerged in the second half of the 1990s. It is part of a line of programming styles that have been proposed, over the course of the evolution of computing, to improve the structuring of programs. The underlying idea is that the better a computer language can structure programs, the easier it will be to design, write, understand, maintain and evolve them. Predecessors of the aspect-oriented programming style include functional programming, procedural programming, modular programming, object-oriented programming and reflective programming. Each of these styles has contributed concepts that make the structure of a program clearer and more readable. Likewise, aspect-oriented programming capitalizes on the experience gained with these programming styles, enabling us to make further progress in structuring computer programs. Aspect-oriented programming does not call into question the programming styles that preceded it. On the contrary, aspect-oriented programming languages continue to build on existing styles, especially object-oriented programming. It complements them by enhancing their ability to write more modular, better-structured programs.

Aspect-oriented programming was born out of the realization that, in many computer programs, the writing of certain functionalities is poorly articulated with the rest of the program, leading to code that is difficult to read, poorly structured and difficult to maintain. These functions are then said to be transversal to the rest of the program. Aspect-oriented programming is based on this observation and introduces the notion of aspect, a new element in the structuring of computer programs that enables cross-functional functions to be written in a clearer, better-structured way, making the program easier to maintain.

Given the lack of concepts for taking cross-functional features into account, aspect-oriented programming tackles the problem of what are the right programming artifacts for transcribing cross-functional features and, above all, how these can be integrated with the rest of the program. To this end, aspect-oriented programming defines the concept of aspect as a set of cuts and plug-ins. Cuts define the aspect's cross-functionality and enable its integration with the rest of the program, while plug-ins define the aspect's behavior.

In this article, we present the basic concepts of aspect programming and illustrate them with the two approaches most commonly used by the aspect programming developer community: the AspectJ language and the Spring AOP framework.