Spring AOP 学习记录2
2021-02-20 15:18
                         标签:targe   步骤   code   问题   epo   tar   ESS   static   put    补充学习一下一些关于Spring AOP的理解     在当前Bean被AnnotationAwareAspectJAutoProxyCreator的postProcessAfterInitialization方法处理的过程中     会需要找到当前Bean可以被应用到的所有advisor.        看代码也知道大致的步骤: 1.findCandidateAdvisors 找到所有的advisor 2.findAdvisorsThatCanApply 过滤出可以使用的advisor   如何找到所有advisor? Creates a Spring Advisor for each AspectJ advice method.
 BF中取到所有的BeanName,并遍历.对于每个BeanName,找到对应的Type(Class).再去找它这个类是否有Aspect.class的注解      从中我们可以看出我们如果要使用AOP有什么样的条件: 1.这个Aspect的类应该要被当做Bean.不然BF中里没有这个Bean的定义.不管是在XML里直接定义BeanDifination还是@Component都OK. 2.这个类应该要有@Aspect.不然怎么知道这个是一个aspect呢.(其实还有一种是compiledByAjc(clazz)..没用过.不清楚怎么用)   找到了Aspect的类以后只要提取其中的advisor即可. List classAdvisors = this.advisorFactory.getAdvisors(factory); 大致核心如下: 对于类的每个没有标记@PointCut的方法   找到这个方法上的Aspect注解(@before..@after...@around...).从中提取出pointcut的表达式即可. Advisor = advise(你的asperct类里的方法) + pointcut(表达式) 最后封装成InstantiationModelAwarePointcutAdvisorImpl并返回.   这里没有太多神奇的操作. 找到所有的advisor以后就是判断每个advisor能不能作用到当前的类上. 怎么判断的? 之前是提出了pointcut的expression.那这里使用这个expr去和类比较一下即可. Advisor委托MethodMatcher去做对应的match. 具体调用比较复杂..我也没有仔细去看...   这个问题可能经常会遇到.我相信80%出现的情况是一个操作数据库的service上的方法a上有@Transaction, 然后方法b是个很一般的方法.b会调用a.然后发现事务没生效.   Spring AOP 学习记录2 标签:targe   步骤   code   问题   epo   tar   ESS   static   put    原文地址:https://www.cnblogs.com/abcwt112/p/12681799.html主题
怎么找到当前Bean可以哪些advisor应用



findCandidateAdvisors
 1 /**
 2      * Look for AspectJ-annotated aspect beans in the current bean factory,
 3      * and return to a list of Spring AOP Advisors representing them.
 4      * 

1         for (Method method : getAdvisorMethods(aspectClass)) {
2             Advisor advisor = getAdvisor(method, lazySingletonAspectInstanceFactory, advisors.size(), aspectName);
3             if (advisor != null) {
4                 advisors.add(advisor);
5             }
6         }
 1     private List
 1     @Override
 2     @Nullable
 3     public Advisor getAdvisor(Method candidateAdviceMethod, MetadataAwareAspectInstanceFactory aspectInstanceFactory,
 4             int declarationOrderInAspect, String aspectName) {
 5 
 6         validate(aspectInstanceFactory.getAspectMetadata().getAspectClass());
 7 
 8         AspectJExpressionPointcut expressionPointcut = getPointcut(
 9                 candidateAdviceMethod, aspectInstanceFactory.getAspectMetadata().getAspectClass());
10         if (expressionPointcut == null) {
11             return null;
12         }
13 
14         return new InstantiationModelAwarePointcutAdvisorImpl(expressionPointcut, candidateAdviceMethod,
15                 this, aspectInstanceFactory, declarationOrderInAspect, aspectName);
16     }
 1     @Nullable
 2     private AspectJExpressionPointcut getPointcut(Method candidateAdviceMethod, Class> candidateAspectClass) {
 3         AspectJAnnotation> aspectJAnnotation =
 4                 AbstractAspectJAdvisorFactory.findAspectJAnnotationOnMethod(candidateAdviceMethod);
 5         if (aspectJAnnotation == null) {
 6             return null;
 7         }
 8 
 9         AspectJExpressionPointcut ajexp =
10                 new AspectJExpressionPointcut(candidateAspectClass, new String[0], new Class>[0]);
11         ajexp.setExpression(aspectJAnnotation.getPointcutExpression());
12         if (this.beanFactory != null) {
13             ajexp.setBeanFactory(this.beanFactory);
14         }
15         return ajexp;
16     }
 1     /**
 2      * Find and return the first AspectJ annotation on the given method
 3      * (there should only be one anyway...).
 4      */
 5     @SuppressWarnings("unchecked")
 6     @Nullable
 7     protected static AspectJAnnotation> findAspectJAnnotationOnMethod(Method method) {
 8         for (Class> clazz : ASPECTJ_ANNOTATION_CLASSES) {
 9             AspectJAnnotation> foundAnnotation = findAnnotation(method, (Class) clazz);
10             if (foundAnnotation != null) {
11                 return foundAnnotation;
12             }
13         }
14         return null;
15     }
1     private static final Class>[] ASPECTJ_ANNOTATION_CLASSES = new Class>[] {
2             Pointcut.class, Around.class, Before.class, After.class, AfterReturning.class, AfterThrowing.class};
findAdvisorsThatCanApply
 1     public static boolean canApply(Advisor advisor, Class> targetClass, boolean hasIntroductions) {
 2         if (advisor instanceof IntroductionAdvisor) {
 3             return ((IntroductionAdvisor) advisor).getClassFilter().matches(targetClass);
 4         }
 5         else if (advisor instanceof PointcutAdvisor) {
 6             PointcutAdvisor pca = (PointcutAdvisor) advisor;
 7             return canApply(pca.getPointcut(), targetClass, hasIntroductions);
 8         }
 9         else {
10             // It doesn‘t have a pointcut so we assume it applies.
11             return true;
12         }
13     }
AOP本类方法掉用本类方法不生效咋办