[[aop-at-aspectj]]
= Declaring an Aspect

With @AspectJ support enabled, any bean defined in your application context with a
class that is an @AspectJ aspect (has the `@Aspect` annotation) is automatically
detected by Spring and used to configure Spring AOP. The next two examples show the
minimal steps required for a not-very-useful aspect.

The first of the two examples shows a regular bean definition in the application context
that points to a bean class that is annotated with `@Aspect`:

include-code::./ApplicationConfiguration[tag=snippet,indent=0]

The second of the two examples shows the `NotVeryUsefulAspect` class definition, which is
annotated with `@Aspect`:

include-code::./NotVeryUsefulAspect[tag=snippet,indent=0]

Aspects (classes annotated with `@Aspect`) can have methods and fields, the same as any
other class. They can also contain pointcut, advice, and introduction (inter-type)
declarations.

.Autodetecting aspects through component scanning
NOTE: You can register aspect classes as regular beans in your Spring XML configuration,
via `@Bean` methods in `@Configuration` classes, or have Spring autodetect them through
classpath scanning -- the same as any other Spring-managed bean. However, note that the
`@Aspect` annotation is not sufficient for autodetection in the classpath. For that
purpose, you need to add a separate `@Component` annotation (or, alternatively, a custom
stereotype annotation that qualifies, as per the rules of Spring's component scanner).

.Advising aspects with other aspects?
NOTE: In Spring AOP, aspects themselves cannot be the targets of advice from other
aspects. The `@Aspect` annotation on a class marks it as an aspect and, hence, excludes
it from auto-proxying.
