Object-oriented programming (OOP) has been presented as a technology that can fundamentally aid software engineering, because the underlying object model provides a better fit with real domain problems. However most software systems consist of several concerns that crosscut multiple modules. Object-oriented techniques for implementing such concerns result in systems that are invasive to implement, tough to understand, and difficult to evolve. This forces the implementation of those design decisions to be scattered throughout the code, resulting in €œtangled€ code that is excessively difficult to develop and maintain. The new aspect-oriented programming (AOP) methodology facilitates modularization of crosscutting concerns. Using AOP, you can create implementations that are easier to design, understand, and maintain. Further, AOP promises higher productivity, improved quality, and better ability to implement newer features.
Abstract:
In computing, aspect-oriented programming (AOP) is a programming paradigm in which secondary or supporting functions are isolated from the main programâ„¢s business logic. It aims to increasemodularity by allowing the separation of cross-cutting concerns, forming a basis for aspect-oriented software development.
AOP includes programming techniques and tools that support the modularization of concerns at the level of the source code, while aspect-oriented software development refers to a whole engineering discipline.
Aspect-oriented programming entails breaking down a program into distinct parts (so-called concerns, cohesive areas of functionality). All programming paradigms support some level of grouping and encapsulation of concerns into separate, independent entities by providing abstractions (e.g. procedures, modules, classes, methods) that can be used for implementing, abstracting and composing these concerns. But some concerns defy these forms of implementation and are called crosscutting concerns because they cut across multiple abstractions in a program.
Logging is a common example of a crosscutting concern because a logging strategy necessarily affects every single logged part of the system. Logging thereby crosscuts all logged classes and methods.
All AOP implementations have some crosscutting expressions that encapsulate each concern in one place. The difference between implementations lies in the power, safety, and usability of the constructs provided. For example, interceptors that specify the methods to intercept express a limited form of crosscutting, without much support for type-safety or debugging. AspectJ has a number of such expressions and encapsulates them in a special class, anaspect. For example, an aspect can alter the behavior of the base code (the non-aspect part of a program) by applying advice (additional behavior) at various join points (points in a program) specified in a quantification or query called a pointcut (that detects whether a given join point matches). An aspect can also make binary-compatible structural changes to other classes, like adding members or parent.