pointcuts

Pointcuts are a core concept in aspect-oriented programming. They define where advice should be applied by selecting a set of join points in a program’s execution.

Join points are well-defined moments during execution, such as method calls, method executions, field access, object construction, or exception handling. A pointcut is a predicate that matches a subset of these join points.

Pointcuts are expressed with designators that match patterns of join points. Common designators include execution and call for method execution and calls, get and set for field access, within and this for scoping, target for the object on which a join point operates, and args for the types of arguments. Annotations and wildcard patterns are also supported, such as execution(* com.example.service..*(..)) to match any method in a package, or @annotation(foo) to match points annotated with a specific annotation.

Pointcuts can be combined using logical operators (and, or, not) to form more precise predicates, for example combining patterns or excluding certain packages. In practice, pointcuts are linked to advice blocks that run before, after, or around a matched join point.

Weaving integrates the aspect code with the base code. This can occur at compile time, load time, or runtime, depending on the framework. The primary goal is to modularize cross-cutting concerns such as logging, security, transactions, and performance monitoring, without duplicating code across modules.

Pointcuts are central to frameworks like AspectJ and Spring AOP. They enable powerful separation of concerns but can increase complexity, so clear documentation and careful design are important.