Implement reliable invocation order for advice within an @Aspect #25186
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type: enhancement
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sbrannen
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Prior to this commit we did not have tests in place to verify the status quo for the invocation order of all advice types when declared within a single aspect, either via the <aop:aspect> XML namespace or AspectJ auto-proxy support. This commit introduces such tests that demonstrate where such ordering is broken or suboptimal. The only test for which the advice invocation order is correct or at least as expected is the afterAdviceTypes() test method in ReflectiveAspectJAdvisorFactoryTests, where an AOP proxy is hand crafted using ReflectiveAspectJAdvisorFactory without the use of Spring's AspectJPrecedenceComparator. See gh-25186
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FelixFly
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FelixFly
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FelixFly
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Prior to this commit we did not have tests in place to verify the status quo for the invocation order of all advice types when declared within a single aspect, either via the <aop:aspect> XML namespace or AspectJ auto-proxy support. This commit introduces such tests that demonstrate where such ordering is broken or suboptimal. The only test for which the advice invocation order is correct or at least as expected is the afterAdviceTypes() test method in ReflectiveAspectJAdvisorFactoryTests, where an AOP proxy is hand crafted using ReflectiveAspectJAdvisorFactory without the use of Spring's AspectJPrecedenceComparator. See spring-projectsgh-25186
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The AspectJPrecedenceComparator was designed to mimic the precedence order enforced by the AspectJ compiler with regard to multiple 'after' methods defined within the same aspect whose pointcuts match the same joinpoint. Specifically, if an aspect declares multiple @after, @AfterReturning, or @AfterThrowing advice methods whose pointcuts match the same joinpoint, such 'after' advice methods should be invoked in the reverse order in which they are declared in the source code. When the AspectJPrecedenceComparator was introduced in Spring Framework 2.0, it achieved its goal of mimicking the AspectJ compiler since the JDK at that time (i.e., Java 5) ensured that an invocation of Class#geDeclaredMethods() returned an array of methods that matched the order of declaration in the source code. However, Java 7 removed this guarantee. Consequently, in Java 7 or higher, AspectJPrecedenceComparator no longer works as it is documented or as it was designed when sorting advice methods in a single @aspect class. Note, however, that AspectJPrecedenceComparator continues to work as documented and designed when sorting advice configured via the <aop:aspect> XML namespace element. PR spring-projectsgh-24673 highlights a use case where AspectJPrecedenceComparator fails to assign the highest precedence to an @after advice method declared last in the source code. Note that an @after advice method with a precedence higher than @AfterReturning and @AfterThrowing advice methods in the same aspect will effectively be invoked last due to the try-finally implementation in AspectJAfterAdvice.invoke() which invokes proceed() in the try-block and invokeAdviceMethod() in the finally-block. Since Spring cannot reliably determine the source code declaration order of annotated advice methods without using ASM to analyze the byte code, this commit introduces reliable invocation order for advice methods declared within a single @aspect. Specifically, the getAdvisors(...) method in ReflectiveAspectJAdvisorFactory now hard codes the declarationOrderInAspect to `0` instead of using the index of the current advice method. This is necessary since the index no longer has any correlation to the method declaration order in the source code. The result is that all advice methods discovered via reflection will now be sorted only according to the precedence rules defined in the ReflectiveAspectJAdvisorFactory.METHOD_COMPARATOR. Specifically, advice methods within a single @aspect will be sorted in the following order (with @after advice methods effectively invoked after @AfterReturning and @AfterThrowing advice methods): @around, @before, @after, @AfterReturning, @AfterThrowing. The modified assertions in AspectJAutoProxyAdviceOrderIntegrationTests demonstrate the concrete effects of this change. Closes spring-projectsgh-25186
FelixFly
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This commit documents the precedence for advice declared within the same @aspect class or within the same <aop:aspect> element. See spring-projectsgh-25186
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Overview
The
AspectJPrecedenceComparatorwas designed to mimic the precedence order enforced by the AspectJ compiler with regard to multiple 'after' methods defined within the same aspect whose pointcuts match the same joinpoint. Specifically, if an aspect declares multiple@After,@AfterReturning, or@AfterThrowingadvice methods whose pointcuts match the same joinpoint, such 'after' advice methods should be invoked in the reverse order in which they are declared in the source code.When the
AspectJPrecedenceComparatorwas introduced in Spring Framework 2.0, it achieved its goal of mimicking the AspectJ compiler since the JDK at that time (i.e., Java 5) ensured that invocations ofClass#geDeclaredMethods()returned an array of methods that matched the order of declaration in the source code. However, Java 7 removed this guarantee. Consequently, in Java 7 or higher,AspectJPrecedenceComparatorno longer works as it is documented or as it was designed.PR #24673 highlights a use case where
AspectJPrecedenceComparatorfails to assign the highest precedence to an@Afteradvice method (declared last in the source code). Note that an@Afteradvice method with a precedence higher than@AfterReturningand@AfterThrowingadvice methods in the same aspect will effectively be invoked last due to the try-finally implementation inAspectJAfterAdvice.invoke(MethodInvocation)which invokesproceed()in the try-block andinvokeAdviceMethod()in the finally-block.Proposal
Since Spring cannot reliably determine the source code declaration order of such advice methods without using ASM to analyze the byte code, we have decided to implement reliable invocation order for 'after' advice methods declared within a single
@Aspect.Related Issues
Deliverables
@After,@AfterReturning, and@AfterThrowingadvice methods within a single@Aspectclass, by ensuring that@AfterReturningand@AfterThrowingmethods are always invoked before any@Aftermethods within the same@Aspectclass.The text was updated successfully, but these errors were encountered: