Simple Introduction to AOP - Session 3

Another way of defining an Aspect is using @AspectJ annotaions - which is natively understood by Spring:

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package org.bk.inventory.aspect;   import org.aspectj.lang.ProceedingJoinPoint; import org.aspectj.lang.annotation.After; import org.aspectj.lang.annotation.Around; import org.aspectj.lang.annotation.Aspect; import org.aspectj.lang.annotation.Before; import org.aspectj.lang.annotation.Pointcut; import org.slf4j.Logger; import org.slf4j.LoggerFactory;   @Aspect public class AuditAspect {       private static Logger logger = LoggerFactory.getLogger(AuditAspect.class);       @Pointcut("execution(* org.bk.inventory.service.*.*(..))")     public void serviceMethods(){         //     }             @Before("serviceMethods()")     public void beforeMethod() {         logger.info("before method");     }       @Around("serviceMethods()")     public Object aroundMethod(ProceedingJoinPoint joinpoint) {         try {             long start = System.nanoTime();             Object result = joinpoint.proceed();             long end = System.nanoTime();             logger.info(String.format("%s took %d ns", joinpoint.getSignature(), (end - start)));             return result;         } catch (Throwable e) {             throw new RuntimeException(e);         }     }             @After("serviceMethods()")     public void afterMethod() {         logger.info("after method");     }    }

The @Aspect annotation on the class identifies it as an aspect definition. It starts by defining the pointcuts:

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1 2	@Pointcut("execution(* org.bk.inventory.service.*.*(..))")     public void serviceMethods(){}

The above basically identifies all the methods of all types in org.bk.inventory.service package, this pointcut is identified by the name of the method on which the annotation is placed - in this case "serviceMethods". Next, the advice is defined using the @Before(serviceMethods()), @After(serviceMethods()) and @Around(serviceMethods()) annotation and the specifics of what needs to happen is the body of the methods with those annotations. Spring AOP natively understands the @AspectJ annotations, if this Aspect is defined as a bean:

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1	<bean id="auditAspect" class="org.bk.inventory.aspect.AuditAspect" />

Spring would create a dynamic proxy to apply the advice on all the target beans identified as part of the pointcut notation.

Links to all sessions on AOP:
AOP Session 1 - Decorator Pattern using Java Dynamic Proxies
AOP Session 2 - Using Spring AOP - xml based configuration
AOP Session 3 - Using Spring AOP - @AspectJ based configuration - with/without compile time weaving
AOP Session 4 - Native AspectJ with compile time weaving
AOP Session 5 - Comprehensive Example