怎样给不同的柱子上添加不同的标准误差线(怎么给柱形图加误差线)
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2022-05-30
2: 扫描容器中的切面,创建 PointcutAdvisor对象
在spring ioc流程加载的过程中,会触发 beanPostProcessor 扩展接口,
而AnnotationAwareAspectJAutoProxyCreator又是SmartInstantiationAwareBeanPostProcessor的子类,所以该扩展接口正是 aop 实现的入口。
该接口的触发在实例化 bean 之后,初始化 bean之前,具体来看:
@Override
public Object postProcessBeforeInstantiation(Class> beanClass, String beanName) throws BeansException {
Object cacheKey = getCacheKey(beanClass, beanName);
if (!StringUtils.hasLength(beanName) || !this.targetSourcedBeans.contains(beanName)) {
//advisedBeans用于存储不可代理的bean,如果包含直接返回
if (this.advisedBeans.containsKey(cacheKey)) {
return null;
}
//判断当前bean是否可以被代理,然后存入advisedBeans
if (isInfrastructureClass(beanClass) || shouldSkip(beanClass, beanName)) {
this.advisedBeans.put(cacheKey, Boolean.FALSE);
return null;
}
}
// Create proxy here if we have a custom TargetSource.
// Suppresses unnecessary default instantiation of the target bean:
// The TargetSource will handle target instances in a custom fashion.
//到这里说明该bean可以被代理,所以去获取自定义目标类,如果没有定义,则跳过。
TargetSource targetSource = getCustomTargetSource(beanClass, beanName);
if (targetSource != null) {
if (StringUtils.hasLength(beanName)) {
this.targetSourcedBeans.add(beanName);
}
Object[] specificInterceptors = getAdvicesAndAdvisorsForBean(beanClass, beanName, targetSource);
Object proxy = createProxy(beanClass, beanName, specificInterceptors, targetSource);
this.proxyTypes.put(cacheKey, proxy.getClass());
//如果最终可以获得代理类,则返回代理类,直接执行实例化后置通知方法
return proxy;
}
return null;
}
来看一下判定 bean 是否被代理的方法依据:
@Override
protected boolean isInfrastructureClass(Class> beanClass) {
return (super.isInfrastructureClass(beanClass) ||
(this.aspectJAdvisorFactory != null && this.aspectJAdvisorFactory.isAspect(beanClass)));
}
private boolean hasAspectAnnotation(Class> clazz) {
//判定当前类是否有 Aspect 注解,如果有,则不能被代理
return (AnnotationUtils.findAnnotation(clazz, Aspect.class) != null);
}
protected boolean isInfrastructureClass(Class> beanClass) {
//判定当前bean是否是 Advice、Pointcut、Advisor、AopInfrastructureBean等子类或实现类,如果是,则不能被代理
boolean retVal = Advice.class.isAssignableFrom(beanClass) ||
Pointcut.class.isAssignableFrom(beanClass) ||
Advisor.class.isAssignableFrom(beanClass) ||
AopInfrastructureBean.class.isAssignableFrom(beanClass);
if (retVal && logger.isTraceEnabled()) {
logger.trace("Did not attempt to auto-proxy infrastructure class [" + beanClass.getName() + "]");
}
return retVal;
}
重点来看 shouldSkip方法:
@Override
protected boolean shouldSkip(Class> beanClass, String beanName) {
// TODO: Consider optimization by caching the list of the aspect names
//获取所有的候选顾问类 Advisor
List
for (Advisor advisor : candidateAdvisors) {
if (advisor instanceof AspectJPointcutAdvisor &&
((AspectJPointcutAdvisor) advisor).getAspectName().equals(beanName)) {
return true;
}
}
return super.shouldSkip(beanClass, beanName);
}
上述代码通过findCandidateAdvisors()方法来获取所有的候选 advisor:
@Override
protected List
// Add all the Spring advisors found according to superclass rules.
//获得 Advisor 实现类
List
// Build Advisors for all AspectJ aspects in the bean factory.
//将@Aspect注解类, 解析成Advisor
if (this.aspectJAdvisorsBuilder != null) {
advisors.addAll(this.aspectJAdvisorsBuilder.buildAspectJAdvisors());
}
return advisors;
}
继续跟进buildAspectJAdvisors方法,会触发
ReflectiveAspectJAdvisorFactory中的getAdvisors方法:
@Override
public List
//从 aspectMetadata 中获取 Aspect()标注的类 class对象
Class> aspectClass = aspectInstanceFactory.getAspectMetadata().getAspectClass();
//获取Aspect()标注的类名
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
//遍历该类所有方法,根据方法判断是否能获取到对应 pointCut,如果有,则生成 advisor 对象
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.
//获取 @DeclareParents 注解修饰的属性(并不常用)
for (Field field : aspectClass.getDeclaredFields()) {
Advisor advisor = getDeclareParentsAdvisor(field);
if (advisor != null) {
advisors.add(advisor);
}
}
return advisors;
}
继续来看getAdvisor方法:
@Override
@Nullable
public Advisor getAdvisor(Method candidateAdviceMethod, MetadataAwareAspectInstanceFactory aspectInstanceFactory,
int declarationOrderInAspect, String aspectName) {
validate(aspectInstanceFactory.getAspectMetadata().getAspectClass());
//根据候选方法名,来获取对应的 pointCut
AspectJExpressionPointcut expressionPointcut = getPointcut(
candidateAdviceMethod, aspectInstanceFactory.getAspectMetadata().getAspectClass());
if (expressionPointcut == null) {
return null;
}
//如果能获取到 pointCut,则将切点表达式 expressionPointcut、当前
对象ReflectiveAspectJAdvisorFactory、 方法名等包装成 advisor 对象
return new InstantiationModelAwarePointcutAdvisorImpl(expressionPointcut, candidateAdviceMethod,
this, aspectInstanceFactory, declarationOrderInAspect, aspectName);
}
可以看到方法将切面相关的类,封装成InstantiationModelAwarePointcutAdvisorImpl对象,也就是Advisor 对象。
来看下上面获取切面的方法,规则就是遍历方法,根据注解判断:
protected static AspectJAnnotation> findAspectJAnnotationOnMethod(Method method) {
//定义class对象数组,如果方法中有以下注解中任何一种,则返回该注解
Class>[] classesToLookFor = new Class>[] {
Before.class, Around.class, After.class, AfterReturning.class, AfterThrowing.class, Pointcut.class};
for (Class> c : classesToLookFor) {
AspectJAnnotation> foundAnnotation = findAnnotation(method, (Class
if (foundAnnotation != null) {
return foundAnnotation;
}
}
return null;
}
我们继续来看 Advisor 对象的构造方法。
InstantiationModelAwarePointcutAdvisorImpl的构造方法会触发构造通知对象:
public Advice getAdvice(Method candidateAdviceMethod, AspectJExpressionPointcut expressionPointcut,
MetadataAwareAspectInstanceFactory aspectInstanceFactory, int declarationOrder, String aspectName) {
//......
//根据注解类型,匹配对应的通知类型
switch (aspectJAnnotation.getAnnotationType()) {
//前置通知
case AtBefore:
springAdvice = new AspectJMethodBeforeAdvice(
candidateAdviceMethod, expressionPointcut, aspectInstanceFactory);
break;
//最终通知
case AtAfter:
springAdvice = new AspectJAfterAdvice(
candidateAdviceMethod, expressionPointcut, aspectInstanceFactory);
break;
//后置通知
case AtAfterReturning:
springAdvice = new AspectJAfterReturningAdvice(
candidateAdviceMethod, expressionPointcut, aspectInstanceFactory);
AfterReturning afterReturningAnnotation = (AfterReturning) aspectJAnnotation.getAnnotation();
if (StringUtils.hasText(afterReturningAnnotation.returning())) {
springAdvice.setReturningName(afterReturningAnnotation.returning());
}
break;
//异常通知
case AtAfterThrowing:
springAdvice = new AspectJAfterThrowingAdvice(
candidateAdviceMethod, expressionPointcut, aspectInstanceFactory);
AfterThrowing afterThrowingAnnotation = (AfterThrowing) aspectJAnnotation.getAnnotation();
if (StringUtils.hasText(afterThrowingAnnotation.throwing())) {
springAdvice.setThrowingName(afterThrowingAnnotation.throwing());
}
break;
//环绕通知
case AtAround:
springAdvice = new AspectJAroundAdvice(
candidateAdviceMethod, expressionPointcut, aspectInstanceFactory);
break;
//切面
case AtPointcut:
if (logger.isDebugEnabled()) {
logger.debug("Processing pointcut '" + candidateAdviceMethod.getName() + "'");
}
return null;
default:
throw new UnsupportedOperationException(
"Unsupported advice type on method: " + candidateAdviceMethod);
}
//......
}
可以看到,根据@Aspect类中方法的注解类型,生成对应的advice,并通过通知的构造方法,将通知增强方法,切面表达式传入到通知当中。
InstantiationModelAwarePointcutAdvisorImpl对象到这里构造完毕。
3: 生成代理类
上面创建advisor的逻辑发生在扩展接口中的postProcessBeforeInstantiation,实例化之前执行,如果有自定义的TargetSource指定类,则则直接生成代理类,并直接执行初始化之后的方法postProcessAfterInitialization。这种情况使用不多,常规代理类还是在postProcessAfterInitialization中创建,也就是 IOC 最后一个扩展方法。
@Override
public Object postProcessAfterInitialization(@Nullable Object bean, String beanName) throws BeansException {
if (bean != null) {
Object cacheKey = getCacheKey(bean.getClass(), beanName);
//处理循环依赖的判断
if (!this.earlyProxyReferences.contains(cacheKey)) {
return wrapIfNecessary(bean, beanName, cacheKey);
}
}
return bean;
}
protected Object wrapIfNecessary(Object bean, String beanName, Object cacheKey) {
if (StringUtils.hasLength(beanName) && this.targetSourcedBeans.contains(beanName)) {
return bean;
}
if (Boolean.FALSE.equals(this.advisedBeans.get(cacheKey))) {
return bean;
}
if (isInfrastructureClass(bean.getClass()) || shouldSkip(bean.getClass(), beanName)) {
this.advisedBeans.put(cacheKey, Boolean.FALSE);
return bean;
}
// Create proxy if we have advice.
//获取到合适的advisor,如果为空。如果不为空,则生成代理类。
Object[] specificInterceptors = getAdvicesAndAdvisorsForBean(bean.getClass(), beanName, null);
if (specificInterceptors != DO_NOT_PROXY) {
this.advisedBeans.put(cacheKey, Boolean.TRUE);
Object proxy = createProxy(
bean.getClass(), beanName, specificInterceptors, new SingletonTargetSource(bean));
this.proxyTypes.put(cacheKey, proxy.getClass());
return proxy;
}
this.advisedBeans.put(cacheKey, Boolean.FALSE);
return bean;
}
上述方法通过调用getAdvicesAndAdvisorsForBean()方法来获取advisor,该方法最终会调用findEligibleAdvisors(),Eligible意为有资格的,合适的。具体来看下:
protected List
List
//这里会对获取的advisor进行筛选
List
//添加一个默认的advisor,执行时用到。
extendAdvisors(eligibleAdvisors);
if (!eligibleAdvisors.isEmpty()) {
eligibleAdvisors = sortAdvisors(eligibleAdvisors);
}
return eligibleAdvisors;
}
最终的筛选规则在AopUtils中:
public static List
//......
for (Advisor candidate : candidateAdvisors) {
if (candidate instanceof IntroductionAdvisor) {
// already processed
continue;
}
//调用 canApply 方法,遍历所有的方法进行匹配
if (canApply(candidate, clazz, hasIntroductions)) {
eligibleAdvisors.add(candidate);
}
}
//......
}
调用canApply方法,遍历被代理类的所有的方法,跟进切面表达式进行匹配,如果有一个方法匹配到,也就意味着该类会被代理。
匹配方法是借助org.aspectj.weaver.internal.tools实现,也就是AspectJ框架中的工具类,有兴趣的可以自行查看。
重点来看一下代理生成方式:
public AopProxy createAopProxy(AdvisedSupport config) throws AopConfigException {
if (config.isOptimize() || config.isProxyTargetClass() || hasNoUserSuppliedProxyInterfaces(config)) {
Class> targetClass = config.getTargetClass();
if (targetClass == null) {
throw new AopConfigException("TargetSource cannot determine target class: " +
"Either an interface or a target is required for proxy creation.");
}
//如果代理目标是接口或者Proxy类型,则走jdk类型
if (targetClass.isInterface() || Proxy.isProxyClass(targetClass)) {
return new JdkDynamicAopProxy(config);
}
return new ObjenesisCglibAopProxy(config);
}
else {
return new JdkDynamicAopProxy(config);
}
}
上述方法通过三个变量来进行筛选代理方法:
· optimize:官方文档翻译为设置代理是否应执行积极的优化,默认为false。
· proxyTargetClass:这个在上面已经提到了,AopAutoConfiguration中指定,默认为true,也就是选择使用 cglib 代理。可以看到该变量和optimize意义一样,之所以这么做,个人理解是为了可以在不同的场景中使用。
· hasNoUserSuppliedProxyInterfaces:是否指定了实现接口。什么意思呢?
hasNoUserSuppliedProxyInterfaces方法如下:
private boolean hasNoUserSuppliedProxyInterfaces(AdvisedSupport config) {
Class>[] ifcs = config.getProxiedInterfaces();
return (ifcs.length == 0 || (ifcs.length == 1 && SpringProxy.class.isAssignableFrom(ifcs[0])));
}
主要就是判断AdvisedSupport中interfaces变量中是否设置了接口,
意思是如果一个类实现了接口,把接口设置到该方法的变量中,但是不是一定会设置到该变量中,具体设置接口的代码如下:
protected Object createProxy(
Class> beanClass, String beanName, Object[] specificInterceptors, TargetSource targetSource) {
//......
if (!proxyFactory.isProxyTargetClass()) {
if (shouldProxyTargetClass(beanClass, beanName)) {
proxyFactory.setProxyTargetClass(true);
}
else {
evaluateProxyInterfaces(beanClass, proxyFactory);
}
}
//......
}
可以看到如果proxyTargetClass为 true,上述方法将不再执行,也就意味着interfaces变量不再赋值。同时,只要为类代理,默认会走 CGLIB 方式。
三:Spring Boot 1.x 版本和 2.x 版本中 AOP配置变动
配置类AopAutoConfiguration:
1.5x版本:
@Configuration
@EnableAspectJAutoProxy(proxyTargetClass = true)
@ConditionalOnProperty(prefix = "spring.aop", name = "proxy-target-class", havingValue = "true", matchIfMissing = false)
public static class CglibAutoProxyConfiguration {
}
2.x版本:
@Configuration
@EnableAspectJAutoProxy(proxyTargetClass = true)
@ConditionalOnProperty(prefix = "spring.aop", name = "proxy-target-class", havingValue = "true", matchIfMissing = true)
public static class CglibAutoProxyConfiguration {
}
在SpringBoot2.x中最主要的变化就是proxy-target-class默认为true,意味着类代理的时候全部走cglib代理方式,只有为接口代理时才走jdk代理(注意:这里为接口代理,不是指代理目标类是否实现了接口)。所以,在使用springboot2.x的版本中,除了代理目标类是接口外,其余的代理方式全部采用cglib类型。
总结
Springboot通过自动装配AopAutoConfiguration配置类,默认自动开启 AOP 功能。通过注册AnnotationAwareAspectJAutoProxyCreator类,来扫描创建所有的Advisor,再通过 Advisor在 Spring IOC的扩展接口中,通过各种设置的匹配规则,来判断是否设置代理,最终生成代理类,注入容器 Spring中
具体代理类如何调用执行呢?后面会详细介绍。
AOP Spring
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