@AspectJ pointcut for all methods of a class with specific annotation

Question

I want to monitor all public methods of all Classes with specified annotation (say @Monitor) (note: Annotation is at class level). What could be a possible pointcut for this? Note: I am using @AspectJ style Spring AOP.

Solution 1

You should combine a type pointcut with a method pointcut.

These pointcuts will do the work to find all public methods inside a class marked with an @Monitor annotation:

@Pointcut("within(@org.rejeev.Monitor *)")
public void beanAnnotatedWithMonitor() {}

@Pointcut("execution(public * *(..))")
public void publicMethod() {}

@Pointcut("publicMethod() && beanAnnotatedWithMonitor()")
public void publicMethodInsideAClassMarkedWithAtMonitor() {}

Advice the last pointcut that combines the first two and you're done!

If you're interested, I have written a cheat sheet with @AspectJ style here with a corresponding example document here.

Solution 2

Using annotations, as described in the question.

Annotation: @Monitor

Annotation on class, app/PagesController.java:

package app;
@Controller
@Monitor
public class PagesController {
    @RequestMapping(value = "/", method = RequestMethod.GET)
    public @ResponseBody String home() {
        return "w00t!";
    }
}

Annotation on method, app/PagesController.java:

package app;
@Controller
public class PagesController {
    @Monitor
    @RequestMapping(value = "/", method = RequestMethod.GET)
    public @ResponseBody String home() {
        return "w00t!";
    }
}

Custom annotation, app/Monitor.java:

package app;
@Component
@Target(value = {ElementType.METHOD, ElementType.TYPE})
@Retention(value = RetentionPolicy.RUNTIME)
public @interface Monitor {
}

Aspect for annotation, app/MonitorAspect.java:

package app;
@Component
@Aspect
public class MonitorAspect {
    @Before(value = "@within(app.Monitor) || @annotation(app.Monitor)")
    public void before(JoinPoint joinPoint) throws Throwable {
        LogFactory.getLog(MonitorAspect.class).info("monitor.before, class: " + joinPoint.getSignature().getDeclaringType().getSimpleName() + ", method: " + joinPoint.getSignature().getName());
    }

    @After(value = "@within(app.Monitor) || @annotation(app.Monitor)")
    public void after(JoinPoint joinPoint) throws Throwable {
        LogFactory.getLog(MonitorAspect.class).info("monitor.after, class: " + joinPoint.getSignature().getDeclaringType().getSimpleName() + ", method: " + joinPoint.getSignature().getName());
    }
}

Enable AspectJ, servlet-context.xml:

<aop:aspectj-autoproxy />

Include AspectJ libraries, pom.xml:

<artifactId>spring-aop</artifactId>
<artifactId>aspectjrt</artifactId>
<artifactId>aspectjweaver</artifactId>
<artifactId>cglib</artifactId>

Solution 3

Something like that:

@Before("execution(* com.yourpackage..*.*(..))")
public void monitor(JoinPoint jp) {
    if (jp.getTarget().getClass().isAnnotationPresent(Monitor.class)) {
       // perform the monitoring actions
    }
}

Note that you must not have any other advice on the same class before this one, because the annotations will be lost after proxying.

Solution 4

Use

@Before("execution(* (@YourAnnotationAtClassLevel *).*(..))")
    public void beforeYourAnnotation(JoinPoint proceedingJoinPoint) throws Throwable {
}

Solution 5

it should be enough to mark your aspect method like this:

@After("@annotation(com.marcot.CommitTransaction)")
    public void after() {

have a look at this for a step by step guide on this.

View more solutions

Comments

[user1098001]

The below one works to an extend. @Pointcut("execution(* (@org.rejeev.Monitor *).*(..))") However now the advice is being executed twice. Any clue?

[user1098001]

Another point is that the @Monitor annotation is on an interface and there a class implements that. Does the presence of a interface and class will cause double execution of such advice?

[fool4jesus]

You should accept the excellent answer below. This gives him reputation. There are precious few people here on SO who can answer AspectJ questions.

[Alex]

that is not answering the original statement, with ElementType.Type

[Donatello]

yes, ElementType.TYPE will also allow to put annotation directly on classes, which I suppose, will result to handle any method in this class. Am i true ? Is it really working ?

[GregHNZ]

Thanks. The discussion of Annotation pointcuts on your Cheat Sheet is particularly useful.

[Priyadarshi Kunal]

How do I get reference to the class in the advice the way I do with normal pointcut advices is @Before("onObjectAction() && this(obj)")

[mwhs]

Nice example. One question: why does the Annotation Monitor have to be a Spring Component?

[Alex]

The Component annotation is used to tell the Spring container to apply include the class in the AspectJ weaver thing. By default, Spring only looks at Controller, Service, and other specific annotations, but not Aspect.

[mwhs]

Ok Thanks. But I was talking about the @Component annotation on the @interface not the Aspect. Why is that needed?

[Alex]

The @Component annotation makes it so Spring will compile it with the AspectJ IoC/DI aspect-oriented system. I don't know how to say it differently. docs.spring.io/spring/docs/3.2.x/spring-framework-reference/‌​…

[xmedeko]

Little simpler execution(public * @Monitor *.*(..)) works, too.

[Yadu Krishnan]

The Cheat Sheet was very helpful, even though it's been 5 years :)

[Lee Meador]

Does this do only "public" methods in the annotated classes or does it do all the methods (no matter what access level)?

[Alex]

I am pretty sure you can intercept private methods as well. What really happens is that AspectJ rewrites the class.

[HVT7]

Just a question here, if two methods that are in hierarchy and both fall under the pointcut and belong to same class, will this execute on both? If Yes, then see stackoverflow.com/questions/37583539/…, because this is not happening in my case.

[josephpconley]

The // perform actions after will never get called since we're returning the value in the line before.

[amstegraf]

I feel execution public is redundant because you can't have a pointcut on private methods