源码分析如何注解使用AOP

た入场券 2022-02-26 21:26 214阅读 0赞

# 如何注解使用AOP #

## 定义注解 ##

/**
     * 在函数上面注解，打印函数调用前后，异常等日志信息
     *
     * <p>用法：@LoggerManage（description="方法描述"）
     *
     * <p>在{@link LoggerAdvice}类中处理
     *
     * @author lishaofeng  396191970@qq.com
     * @date 2018年11月13日 下午2:39:10
     */
    @Target(ElementType.METHOD)
    @Retention(RetentionPolicy.RUNTIME)
    @Documented
    public @interface LoggerManage {
    
        /**
         * 方法描述信息
         * @return
         */
        String description();
    }

## AOP增强处理 ##

/**
     * 通过注解{@link LoggerManage}来打印日志
     * @author lishaofeng  396191970@qq.com
     * @date 2018年11月13日 下午2:39:06
     */
    @Aspect
    @Component
    @Slf4j
    public class LoggerAdvice {
    
    	@Around(value= "within(com.jlpay..*) && @annotation(loggerManage)")
    	public Object addAroundLogger(ProceedingJoinPoint joinPoint, LoggerManage loggerManage)
    	{
    		log.info("执行【{}】开始,函数名【{}】,传入参数【{}】", loggerManage.description(),joinPoint.getSignature().getName(),JSON.toJSONString(joinPoint.getArgs()));
    
    		Object oj = null;
    		try {
    			oj = joinPoint.proceed();
    			log.info("执行【{}】结束,函数名【{}】,返回数据【{}】" , loggerManage.description(),joinPoint.getSignature().getName(),JSON.toJSONString(oj));
    
    		} catch ( Throwable e) {
    			e.printStackTrace();
    			log.error("执行【{}】,函数名【{}】,异常【{}】" ,loggerManage.description(),joinPoint.getSignature().getName(),e.getMessage());
    		}
    		return oj;
    
    	}
    
    
    }

## 配置 ##

/**
     *自动配置类，注入{@link LoggerAdvice}类到容器
     * @author 39619
     */
    @Configuration
    @EnableAspectJAutoProxy
    @Import(LoggerAdvice.class)
    public class LoggerConfig {
    }

**以上就是注解AOP的使用方法。**

知其然不知其所以然可不行，究竟是如何将自定义注解注入到函数方法中的参数？

## 如何将注解注入到函数方法中的参数？ ##

通过断点到LoggerAdvice.addAroundLogger（），堆栈信息如下：

addAroundLogger:24, LoggerAdvice (com.jlpay.common.log)
    invoke0:-1, NativeMethodAccessorImpl (sun.reflect)
    invoke:62, NativeMethodAccessorImpl (sun.reflect)
    invoke:43, DelegatingMethodAccessorImpl (sun.reflect)
    invoke:498, Method (java.lang.reflect)
    invokeAdviceMethodWithGivenArgs:644, AbstractAspectJAdvice (org.springframework.aop.aspectj)
    invokeAdviceMethod:633, AbstractAspectJAdvice (org.springframework.aop.aspectj)
    invoke:70, AspectJAroundAdvice (org.springframework.aop.aspectj)
    proceed:174, ReflectiveMethodInvocation (org.springframework.aop.framework)
    invoke:92, ExposeInvocationInterceptor (org.springframework.aop.interceptor)
    proceed:185, ReflectiveMethodInvocation (org.springframework.aop.framework)
    intercept:688, CglibAopProxy$DynamicAdvisedInterceptor (org.springframework.aop.framework)
    gateway:-1, ApiTransController$$EnhancerBySpringCGLIB$$39469408 (com.jlpay.quickpass.api.trans.controller)
    ...

## AbstractAspectJAdvice ##

发现是在 invokeAdviceMethod:633, AbstractAspectJAdvice (org.springframework.aop.aspectj）中注入方法参数的

// As above, but in this case we are given the join point.
    	protected Object invokeAdviceMethod(JoinPoint jp, @Nullable JoinPointMatch jpMatch,
    			@Nullable Object returnValue, @Nullable Throwable t) throws Throwable {
    
    		return invokeAdviceMethodWithGivenArgs(argBinding(jp, jpMatch, returnValue, t));
    	}

/**
    	 * Take the arguments at the method execution join point and output a set of arguments
    	 * to the advice method
    	 * @param jp the current JoinPoint
    	 * @param jpMatch the join point match that matched this execution join point
    	 * @param returnValue the return value from the method execution (may be null)
    	 * @param ex the exception thrown by the method execution (may be null)
    	 * @return the empty array if there are no arguments
    	 */
    	protected Object[] argBinding(JoinPoint jp, @Nullable JoinPointMatch jpMatch,
    			@Nullable Object returnValue, @Nullable Throwable ex) {
    
    		calculateArgumentBindings();
    
    		// AMC start
    		Object[] adviceInvocationArgs = new Object[this.parameterTypes.length];
    		int numBound = 0;
    
    		if (this.joinPointArgumentIndex != -1) {
    			adviceInvocationArgs[this.joinPointArgumentIndex] = jp;
    			numBound++;
    		}
    		else if (this.joinPointStaticPartArgumentIndex != -1) {
    			adviceInvocationArgs[this.joinPointStaticPartArgumentIndex] = jp.getStaticPart();
    			numBound++;
    		}
    
    		if (!CollectionUtils.isEmpty(this.argumentBindings)) {
    			// binding from pointcut match
    			if (jpMatch != null) {
    				PointcutParameter[] parameterBindings = jpMatch.getParameterBindings();
    				for (PointcutParameter parameter : parameterBindings) {
    					String name = parameter.getName();
    					Integer index = this.argumentBindings.get(name);
    					adviceInvocationArgs[index] = parameter.getBinding();
    					numBound++;
    				}
    			}
    			// binding from returning clause
    			if (this.returningName != null) {
    				Integer index = this.argumentBindings.get(this.returningName);
    				adviceInvocationArgs[index] = returnValue;
    				numBound++;
    			}
    			// binding from thrown exception
    			if (this.throwingName != null) {
    				Integer index = this.argumentBindings.get(this.throwingName);
    				adviceInvocationArgs[index] = ex;
    				numBound++;
    			}
    		}
    
    		if (numBound != this.parameterTypes.length) {
    			throw new IllegalStateException("Required to bind " + this.parameterTypes.length +
    					" arguments, but only bound " + numBound + " (JoinPointMatch " +
    					(jpMatch == null ? "was NOT" : "WAS") + " bound in invocation)");
    		}
    
    		return adviceInvocationArgs;
    	}

这里通过JoinPointMatch对象，获取绑定的 @LoggerManage（description=“方法描述”） 注解 ，然后根据顺序一个个给参数数组Object\[\] adviceInvocationArgs 赋值。就这样我们的AOP增强方法就获取到了自定义注解![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzE1Mjg4MDIz_size_16_color_FFFFFF_t_70]  
注意：  
这里参数有顺序要求，  
\[JoinPoint\] \[StaticPart\] \[匹配的切入点绑定的（比如注解）\] \[返回对象\] \[异常对象\]

**以上就是是如何将自定义注解注入到函数方法中的参数**

## AbstractAspectJAdvice是什么时候注入的呢？ ##

断点到 AbstractAspectJAdvice，堆栈信息如下：

<clinit>:68, AbstractAspectJAdvice (org.springframework.aop.aspectj)
    getAdvice:274, ReflectiveAspectJAdvisorFactory (org.springframework.aop.aspectj.annotation)
    instantiateAdvice:167, InstantiationModelAwarePointcutAdvisorImpl (org.springframework.aop.aspectj.annotation)
    <init>:113, InstantiationModelAwarePointcutAdvisorImpl (org.springframework.aop.aspectj.annotation)
    getAdvisor:198, ReflectiveAspectJAdvisorFactory (org.springframework.aop.aspectj.annotation)
    getAdvisors:126, ReflectiveAspectJAdvisorFactory (org.springframework.aop.aspectj.annotation)
    buildAspectJAdvisors:110, BeanFactoryAspectJAdvisorsBuilder (org.springframework.aop.aspectj.annotation)
    findCandidateAdvisors:95, AnnotationAwareAspectJAutoProxyCreator (org.springframework.aop.aspectj.annotation)
    shouldSkip:101, AspectJAwareAdvisorAutoProxyCreator (org.springframework.aop.aspectj.autoproxy)
    postProcessBeforeInstantiation:254, AbstractAutoProxyCreator (org.springframework.aop.framework.autoproxy)
    applyBeanPostProcessorsBeforeInstantiation:1060, AbstractAutowireCapableBeanFactory (org.springframework.beans.factory.support)
    ...

根据堆栈信息可以看到是通过 AbstractAutoProxyCreator.applyBeanPostProcessorsBeforeInstantiation（）bean初始化前置处理，调用子类AspectJAwareAdvisorAutoProxyCreator.shouldSkip（）方法来找全部匹配的Advisors再调用 BeanFactoryAspectJAdvisorsBuilder委托AspectJAdvisorFactory.getAdvisors(factory)获取全部的Advisors。

@Override
    	protected boolean shouldSkip(Class<?> beanClass, String beanName) {
    		// TODO: Consider optimization by caching the list of the aspect names
    		List<Advisor> candidateAdvisors = findCandidateAdvisors();
    		for (Advisor advisor : candidateAdvisors) {
    			if (advisor instanceof AspectJPointcutAdvisor &&
    					((AspectJPointcutAdvisor) advisor).getAspectName().equals(beanName)) {
    				return true;
    			}
    		}
    		return super.shouldSkip(beanClass, beanName);
    	}

@Override
    	protected List<Advisor> findCandidateAdvisors() {
    		// Add all the Spring advisors found according to superclass rules.
    		List<Advisor> advisors = super.findCandidateAdvisors();
    		// Build Advisors for all AspectJ aspects in the bean factory.
    		if (this.aspectJAdvisorsBuilder != null) {
    			advisors.addAll(this.aspectJAdvisorsBuilder.buildAspectJAdvisors());
    		}
    		return advisors;
    	}

这里会查找Spring容器里面的所有类，遍历判断有Aspect注解的类，才去生成Advisors

/**
    	 * Look for AspectJ-annotated aspect beans in the current bean factory,
    	 * and return to a list of Spring AOP Advisors representing them.
    	 * <p>Creates a Spring Advisor for each AspectJ advice method.
    	 * @return the list of {@link org.springframework.aop.Advisor} beans
    	 * @see #isEligibleBean
    	 */
    	public List<Advisor> buildAspectJAdvisors() {
    		List<String> aspectNames = this.aspectBeanNames;
    
    		if (aspectNames == null) {
    			synchronized (this) {
    				aspectNames = this.aspectBeanNames;
    				if (aspectNames == null) {
    					List<Advisor> advisors = new ArrayList<>();
    					aspectNames = new ArrayList<>();
    					String[] beanNames = BeanFactoryUtils.beanNamesForTypeIncludingAncestors(
    							this.beanFactory, Object.class, true, false);
    					for (String beanName : beanNames) {
    						if (!isEligibleBean(beanName)) {
    							continue;
    						}
    						// We must be careful not to instantiate beans eagerly as in this case they
    						// would be cached by the Spring container but would not have been weaved.
    						Class<?> beanType = this.beanFactory.getType(beanName);
    						if (beanType == null) {
    							continue;
    						}
    						if (this.advisorFactory.isAspect(beanType)) {
    							aspectNames.add(beanName);
    							AspectMetadata amd = new AspectMetadata(beanType, beanName);
    							if (amd.getAjType().getPerClause().getKind() == PerClauseKind.SINGLETON) {
    								MetadataAwareAspectInstanceFactory factory =
    										new BeanFactoryAspectInstanceFactory(this.beanFactory, beanName);
    								List<Advisor> classAdvisors = this.advisorFactory.getAdvisors(factory);
    								if (this.beanFactory.isSingleton(beanName)) {
    									this.advisorsCache.put(beanName, classAdvisors);
    								}
    								else {
    									this.aspectFactoryCache.put(beanName, factory);
    								}
    								advisors.addAll(classAdvisors);
    							}
    							else {
    								// Per target or per this.
    								if (this.beanFactory.isSingleton(beanName)) {
    									throw new IllegalArgumentException("Bean with name '" + beanName +
    											"' is a singleton, but aspect instantiation model is not singleton");
    								}
    								MetadataAwareAspectInstanceFactory factory =
    										new PrototypeAspectInstanceFactory(this.beanFactory, beanName);
    								this.aspectFactoryCache.put(beanName, factory);
    								advisors.addAll(this.advisorFactory.getAdvisors(factory));
    							}
    						}
    					}
    					this.aspectBeanNames = aspectNames;
    					return advisors;
    				}
    			}
    		}
    
    		if (aspectNames.isEmpty()) {
    			return Collections.emptyList();
    		}
    		List<Advisor> advisors = new ArrayList<>();
    		for (String aspectName : aspectNames) {
    			List<Advisor> cachedAdvisors = this.advisorsCache.get(aspectName);
    			if (cachedAdvisors != null) {
    				advisors.addAll(cachedAdvisors);
    			}
    			else {
    				MetadataAwareAspectInstanceFactory factory = this.aspectFactoryCache.get(aspectName);
    				advisors.addAll(this.advisorFactory.getAdvisors(factory));
    			}
    		}
    		return advisors;
    	}

@Override
    	public boolean isAspect(Class<?> clazz) {
    		return (hasAspectAnnotation(clazz) && !compiledByAjc(clazz));
    	}

private boolean hasAspectAnnotation(Class<?> clazz) {
    		return (AnnotationUtils.findAnnotation(clazz, Aspect.class) != null);
    	}

实际是通过AspectJAdvisorFactory的子类ReflectiveAspectJAdvisorFactory通过反射的形式获取。

@Override
    	public List<Advisor> getAdvisors(MetadataAwareAspectInstanceFactory aspectInstanceFactory) {
    		Class<?> aspectClass = aspectInstanceFactory.getAspectMetadata().getAspectClass();
    		String aspectName = aspectInstanceFactory.getAspectMetadata().getAspectName();
    		validate(aspectClass);
    
    		// We need to wrap the MetadataAwareAspectInstanceFactory with a decorator
    		// so that it will only instantiate once.
    		MetadataAwareAspectInstanceFactory lazySingletonAspectInstanceFactory =
    				new LazySingletonAspectInstanceFactoryDecorator(aspectInstanceFactory);
    
    		List<Advisor> advisors = new ArrayList<>();
    		for (Method method : getAdvisorMethods(aspectClass)) {
    			Advisor advisor = getAdvisor(method, lazySingletonAspectInstanceFactory, advisors.size(), aspectName);
    			if (advisor != null) {
    				advisors.add(advisor);
    			}
    		}
    
    		// If it's a per target aspect, emit the dummy instantiating aspect.
    		if (!advisors.isEmpty() && lazySingletonAspectInstanceFactory.getAspectMetadata().isLazilyInstantiated()) {
    			Advisor instantiationAdvisor = new SyntheticInstantiationAdvisor(lazySingletonAspectInstanceFactory);
    			advisors.add(0, instantiationAdvisor);
    		}
    
    		// Find introduction fields.
    		for (Field field : aspectClass.getDeclaredFields()) {
    			Advisor advisor = getDeclareParentsAdvisor(field);
    			if (advisor != null) {
    				advisors.add(advisor);
    			}
    		}
    
    		return advisors;
    	}

获取非Pointcut注解的函数

private List<Method> getAdvisorMethods(Class<?> aspectClass) {
    		final List<Method> methods = new ArrayList<>();
    		ReflectionUtils.doWithMethods(aspectClass, method -> {
    			// Exclude pointcuts
    			if (AnnotationUtils.getAnnotation(method, Pointcut.class) == null) {
    				methods.add(method);
    			}
    		});
    		methods.sort(METHOD_COMPARATOR);
    		return methods;
    	}

@Override
    	@Nullable
    	public Advisor getAdvisor(Method candidateAdviceMethod, MetadataAwareAspectInstanceFactory aspectInstanceFactory,
    			int declarationOrderInAspect, String aspectName) {
    
    		validate(aspectInstanceFactory.getAspectMetadata().getAspectClass());
    
    		AspectJExpressionPointcut expressionPointcut = getPointcut(
    				candidateAdviceMethod, aspectInstanceFactory.getAspectMetadata().getAspectClass());
    		if (expressionPointcut == null) {
    			return null;
    		}
    
    		return new InstantiationModelAwarePointcutAdvisorImpl(expressionPointcut, candidateAdviceMethod,
    				this, aspectInstanceFactory, declarationOrderInAspect, aspectName);
    	}

最终调用ReflectiveAspectJAdvisorFactory 判断 aspectJAnnotation.getAnnotationType() 来创建实际的Advice

@Override
    	@Nullable
    	public Advice getAdvice(Method candidateAdviceMethod, AspectJExpressionPointcut expressionPointcut,
    			MetadataAwareAspectInstanceFactory aspectInstanceFactory, int declarationOrder, String aspectName) {
    
    		Class<?> candidateAspectClass = aspectInstanceFactory.getAspectMetadata().getAspectClass();
    		validate(candidateAspectClass);
    
    		AspectJAnnotation<?> aspectJAnnotation =
    				AbstractAspectJAdvisorFactory.findAspectJAnnotationOnMethod(candidateAdviceMethod);
    		if (aspectJAnnotation == null) {
    			return null;
    		}
    
    		// If we get here, we know we have an AspectJ method.
    		// Check that it's an AspectJ-annotated class
    		if (!isAspect(candidateAspectClass)) {
    			throw new AopConfigException("Advice must be declared inside an aspect type: " +
    					"Offending method '" + candidateAdviceMethod + "' in class [" +
    					candidateAspectClass.getName() + "]");
    		}
    
    		if (logger.isDebugEnabled()) {
    			logger.debug("Found AspectJ method: " + candidateAdviceMethod);
    		}
    
    		AbstractAspectJAdvice springAdvice;
    
    		switch (aspectJAnnotation.getAnnotationType()) {
    			case AtBefore:
    				springAdvice = new AspectJMethodBeforeAdvice(
    						candidateAdviceMethod, expressionPointcut, aspectInstanceFactory);
    				break;
    			case AtAfter:
    				springAdvice = new AspectJAfterAdvice(
    						candidateAdviceMethod, expressionPointcut, aspectInstanceFactory);
    				break;
    			case AtAfterReturning:
    				springAdvice = new AspectJAfterReturningAdvice(
    						candidateAdviceMethod, expressionPointcut, aspectInstanceFactory);
    				AfterReturning afterReturningAnnotation = (AfterReturning) aspectJAnnotation.getAnnotation();
    				if (StringUtils.hasText(afterReturningAnnotation.returning())) {
    					springAdvice.setReturningName(afterReturningAnnotation.returning());
    				}
    				break;
    			case AtAfterThrowing:
    				springAdvice = new AspectJAfterThrowingAdvice(
    						candidateAdviceMethod, expressionPointcut, aspectInstanceFactory);
    				AfterThrowing afterThrowingAnnotation = (AfterThrowing) aspectJAnnotation.getAnnotation();
    				if (StringUtils.hasText(afterThrowingAnnotation.throwing())) {
    					springAdvice.setThrowingName(afterThrowingAnnotation.throwing());
    				}
    				break;
    			case AtAround:
    				springAdvice = new AspectJAroundAdvice(
    						candidateAdviceMethod, expressionPointcut, aspectInstanceFactory);
    				break;
    			case AtPointcut:
    				if (logger.isDebugEnabled()) {
    					logger.debug("Processing pointcut '" + candidateAdviceMethod.getName() + "'");
    				}
    				return null;
    			default:
    				throw new UnsupportedOperationException(
    						"Unsupported advice type on method: " + candidateAdviceMethod);
    		}
    
    		// Now to configure the advice...
    		springAdvice.setAspectName(aspectName);
    		springAdvice.setDeclarationOrder(declarationOrder);
    		String[] argNames = this.parameterNameDiscoverer.getParameterNames(candidateAdviceMethod);
    		if (argNames != null) {
    			springAdvice.setArgumentNamesFromStringArray(argNames);
    		}
    		springAdvice.calculateArgumentBindings();
    
    		return springAdvice;
    	}

**到这里 AbstractAspectJAdvice 就创建好了。**

## 上面提到的AspectJAwareAdvisorAutoProxyCreator是如何注入的？ ##

### @EnableAspectJAutoProxy ###

@Target(ElementType.TYPE)
    @Retention(RetentionPolicy.RUNTIME)
    @Documented
    @Import(AspectJAutoProxyRegistrar.class)
    public @interface EnableAspectJAutoProxy {

Spriing容器启动refresh方法，会调用处理器去注册bean，从而识别@EnableAspectJAutoProxy注解的@Import(AspectJAutoProxyRegistrar.class)注解去注册AspectJAutoProxyRegistrar类。  
AspectJAutoProxyRegistrar类会调用AopConfigUtils.registerAspectJAnnotationAutoProxyCreatorIfNecessary(registry);从而注册AnnotationAwareAspectJAutoProxyCreator类

@Nullable
    	public static BeanDefinition registerAspectJAnnotationAutoProxyCreatorIfNecessary(BeanDefinitionRegistry registry,
    			@Nullable Object source) {
    
    		return registerOrEscalateApcAsRequired(AnnotationAwareAspectJAutoProxyCreator.class, registry, source);
    	}

AnnotationAwareAspectJAutoProxyCreator 继承AspectJAwareAdvisorAutoProxyCreator  
**到此AspectJAwareAdvisorAutoProxyCreator注册成功**

public class AnnotationAwareAspectJAutoProxyCreator extends AspectJAwareAdvisorAutoProxyCreator {

# 总结 #

Spirng 容器启动时 通过@EnableAspectJAutoProxy 导入注册AspectJAutoProxyRegistrar，然后注册了AnnotationAwareAspectJAutoProxyCreator类。  
AnnotationAwareAspectJAutoProxyCreator 被调用bean初始化前置处理，为匹配切入表达式的方法，AOP增强处理（自动配备增强方法参数），注册增强后的对象注册到Spring容器中。从而实现AOP功能。

[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzE1Mjg4MDIz_size_16_color_FFFFFF_t_70]: /images/20220227/7ec7e88060d94837a62bd462f5357a58.png