Editing Aspect-oriented programming (section)

{{Short description|Programming paradigm}}
{{Use dmy dates|date=June 2023}}

In [[computing]], '''aspect-oriented programming''' ('''AOP''') is a [[programming paradigm]] that aims to increase [[Modularity (programming)|modularity]] by allowing the [[separation of concerns|separation of]] [[cross-cutting concern]]s. It does so by adding behavior to existing code (an [[Advice (programming)|advice]]) ''without'' modifying the code, instead separately specifying which code is modified via a "[[pointcut]]" specification, such as "log all function calls when the function's name begins with 'set{{'"}}. This allows behaviors that are not central to the [[business logic]] (such as logging) to be added to a program without cluttering the code of core functions.

AOP includes programming methods 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 program logic into cohesive areas of functionality (so-called ''concerns''). Nearly all programming paradigms support some level of grouping and [[encapsulation (computer science)|encapsulation]] of concerns into separate, independent entities by providing abstractions (e.g., functions, procedures, modules, classes, methods) that can be used for implementing, abstracting, and composing these concerns. Some concerns "cut across" multiple abstractions in a program, and defy these forms of implementation. These concerns are called ''cross-cutting concerns'' or horizontal concerns.

[[Logging (computing)|Logging]] exemplifies a cross-cutting concern because a logging strategy must affect every logged part of the system. Logging thereby ''crosscuts'' all logged classes and methods.

All AOP implementations have some cross-cutting 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 express a limited form of cross-cutting, without much support for type-safety or debugging. [[AspectJ]] has a number of such expressions and encapsulates them in a special class, called an [[aspect (computer science)|aspect]]. For example, an aspect can alter the behavior of the base code (the non-aspect part of a program) by applying [[Advice in aspect-oriented programming|advice]] (additional behavior) at various [[join point]]s (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, such as adding members or parents.