@Target(ElementType.TYPE)
@Retention(RetentionPolicy.RUNTIME)
@Documented
@Import(AsyncConfigurationSelector.class)
public @interface EnableAsync {
    /**
     * Indicate the 'async' annotation type to be detected at either class
     * or method level.
     * <p>By default, both Spring's @{@link Async} annotation and the EJB 3.1
     * {@code @javax.ejb.Asynchronous} annotation will be detected.
     * <p>This attribute exists so that developers can provide their own
     * custom annotation type to indicate that a method (or all methods of
     * a given class) should be invoked asynchronously.
     */
    Class<? extends Annotation> annotation() default Annotation.class;
    /**
     * Indicate whether subclass-based (CGLIB) proxies are to be created as opposed
     * to standard Java interface-based proxies.
     * <p><strong>Applicable only if the {@link #mode} is set to {@link AdviceMode#PROXY}</strong>.
     * <p>The default is {@code false}.
     * <p>Note that setting this attribute to {@code true} will affect <em>all</em>
     * Spring-managed beans requiring proxying, not just those marked with {@code @Async}.
     * For example, other beans marked with Spring's {@code @Transactional} annotation
     * will be upgraded to subclass proxying at the same time. This approach has no
     * negative impact in practice unless one is explicitly expecting one type of proxy
     * vs. another &mdash; for example, in tests.
     */
    boolean proxyTargetClass() default false;
    /**
     * Indicate how async advice should be applied.
     * <p><b>The default is {@link AdviceMode#PROXY}.</b>
     * Please note that proxy mode allows for interception of calls through the proxy
     * only. Local calls within the same class cannot get intercepted that way; an
     * {@link Async} annotation on such a method within a local call will be ignored
     * since Spring's interceptor does not even kick in for such a runtime scenario.
     * For a more advanced mode of interception, consider switching this to
     * {@link AdviceMode#ASPECTJ}.
     */
    AdviceMode mode() default AdviceMode.PROXY;
    /**
     * Indicate the order in which the {@link AsyncAnnotationBeanPostProcessor}
     * should be applied.
     * <p>The default is {@link Ordered#LOWEST_PRECEDENCE} in order to run
     * after all other post-processors, so that it can add an advisor to
     * existing proxies rather than double-proxy.
     */
    int order() default Ordered.LOWEST_PRECEDENCE;
}

@Override
@Nullable
public String[] selectImports(AdviceMode adviceMode) {
    switch (adviceMode) {
        case PROXY:
            return new String[] {ProxyAsyncConfiguration.class.getName()};
        case ASPECTJ:
            return new String[] {ASYNC_EXECUTION_ASPECT_CONFIGURATION_CLASS_NAME};
        default:
            return null;
    }
}

@Configuration
@Role(BeanDefinition.ROLE_INFRASTRUCTURE)
public class ProxyAsyncConfiguration extends AbstractAsyncConfiguration {
    @Bean(name = TaskManagementConfigUtils.ASYNC_ANNOTATION_PROCESSOR_BEAN_NAME)
    @Role(BeanDefinition.ROLE_INFRASTRUCTURE)
    public AsyncAnnotationBeanPostProcessor asyncAdvisor() {
        Assert.notNull(this.enableAsync, "@EnableAsync annotation metadata was not injected");
        AsyncAnnotationBeanPostProcessor bpp = new AsyncAnnotationBeanPostProcessor();
        bpp.configure(this.executor, this.exceptionHandler);
        Class<? extends Annotation> customAsyncAnnotation = this.enableAsync.getClass("annotation");
        if (customAsyncAnnotation != AnnotationUtils.getDefaultValue(EnableAsync.class, "annotation")) {
            bpp.setAsyncAnnotationType(customAsyncAnnotation);
        }
        bpp.setProxyTargetClass(this.enableAsync.getBoolean("proxyTargetClass"));
        bpp.setOrder(this.enableAsync.<Integer>getNumber("order"));
        return bpp;
    }
}

@Configuration
public abstract class AbstractAsyncConfiguration implements ImportAware {
    .....
    
    /**
     * Collect any {@link AsyncConfigurer} beans through autowiring.
     */
    @Autowired(required = false)
    void setConfigurers(Collection<AsyncConfigurer> configurers) {
        if (CollectionUtils.isEmpty(configurers)) {
            return;
        }
        if (configurers.size() > 1) {
            throw new IllegalStateException("Only one AsyncConfigurer may exist");
        }
        AsyncConfigurer configurer = configurers.iterator().next();
        this.executor = configurer::getAsyncExecutor;
        this.exceptionHandler = configurer::getAsyncUncaughtExceptionHandler;
    }
}

public class AsyncAnnotationBeanPostProcessor extends AbstractBeanFactoryAwareAdvisingPostProcessor {
    ....
    @Override
    public void setBeanFactory(BeanFactory beanFactory) {
        super.setBeanFactory(beanFactory);
        AsyncAnnotationAdvisor advisor = new AsyncAnnotationAdvisor(this.executor, this.exceptionHandler);
        if (this.asyncAnnotationType != null) {
            advisor.setAsyncAnnotationType(this.asyncAnnotationType);
        }
        advisor.setBeanFactory(beanFactory);
        this.advisor = advisor;
    }
}

protected Advice buildAdvice(
        @Nullable Supplier<Executor> executor, @Nullable Supplier<AsyncUncaughtExceptionHandler> exceptionHandler) {
    AnnotationAsyncExecutionInterceptor interceptor = new AnnotationAsyncExecutionInterceptor(null);
    interceptor.configure(executor, exceptionHandler);
    return interceptor;
}

public Object invoke(final MethodInvocation invocation) throws Throwable {
    Class<?> targetClass = (invocation.getThis() != null ? AopUtils.getTargetClass(invocation.getThis()) : null);
    Method specificMethod = ClassUtils.getMostSpecificMethod(invocation.getMethod(), targetClass);
    final Method userDeclaredMethod = BridgeMethodResolver.findBridgedMethod(specificMethod);
    AsyncTaskExecutor executor = determineAsyncExecutor(userDeclaredMethod);
    if (executor == null) {
        throw new IllegalStateException(
                "No executor specified and no default executor set on AsyncExecutionInterceptor either");
    }
    Callable<Object> task = () -> {
        try {
            Object result = invocation.proceed();
            if (result instanceof Future) {
                return ((Future<?>) result).get();
            }
        }
        catch (ExecutionException ex) {
            handleError(ex.getCause(), userDeclaredMethod, invocation.getArguments());
        }
        catch (Throwable ex) {
            handleError(ex, userDeclaredMethod, invocation.getArguments());
        }
        return null;
    };
    return doSubmit(task, executor, invocation.getMethod().getReturnType());
}

public interface Pointcut {
    /**
     * Return the ClassFilter for this pointcut.
     * @return the ClassFilter (never {@code null})
     */
    ClassFilter getClassFilter();
    /**
     * Return the MethodMatcher for this pointcut.
     * @return the MethodMatcher (never {@code null})
     */
    MethodMatcher getMethodMatcher();
    /**
     * Canonical Pointcut instance that always matches.
     */
    Pointcut TRUE = TruePointcut.INSTANCE;
}
public interface Pointcut {
    /**
     * Return the ClassFilter for this pointcut.
     * @return the ClassFilter (never {@code null})
     */
    ClassFilter getClassFilter();
    /**
     * Return the MethodMatcher for this pointcut.
     * @return the MethodMatcher (never {@code null})
     */
    MethodMatcher getMethodMatcher();
    /**
     * Canonical Pointcut instance that always matches.
     */
    Pointcut TRUE = TruePointcut.INSTANCE;
}

@Override
protected ProxyFactory prepareProxyFactory(Object bean, String beanName) {
    if (this.beanFactory != null) {
        AutoProxyUtils.exposeTargetClass(this.beanFactory, beanName, bean.getClass());
    }
    ProxyFactory proxyFactory = super.prepareProxyFactory(bean, beanName);
    if (!proxyFactory.isProxyTargetClass() && this.beanFactory != null &&
            AutoProxyUtils.shouldProxyTargetClass(this.beanFactory, beanName)) {
        proxyFactory.setProxyTargetClass(true);
    }
    return proxyFactory;
}

@Override
protected boolean isEligible(Object bean, String beanName) {
    return (!AutoProxyUtils.isOriginalInstance(beanName, bean.getClass()) &&
            super.isEligible(bean, beanName));
}

AbstractAdvisingBeanPostProcessor.java
protected boolean isEligible(Class<?> targetClass) {
    Boolean eligible = this.eligibleBeans.get(targetClass);
    if (eligible != null) {
        return eligible;
    }
    if (this.advisor == null) {
        return false;
    }
    eligible = AopUtils.canApply(this.advisor, targetClass);
    this.eligibleBeans.put(targetClass, eligible);
    return eligible;
}

AopUtils.java
public static boolean canApply(Advisor advisor, Class<?> targetClass, boolean hasIntroductions) {
    if (advisor instanceof IntroductionAdvisor) {
        return ((IntroductionAdvisor) advisor).getClassFilter().matches(targetClass);
    }
    else if (advisor instanceof PointcutAdvisor) {
        PointcutAdvisor pca = (PointcutAdvisor) advisor;
        return canApply(pca.getPointcut(), targetClass, hasIntroductions);
    }
    else {
        // It doesn't have a pointcut so we assume it applies.
        return true;
    }
}

public Object postProcessAfterInitialization(Object bean, String beanName) {
    if (this.advisor == null || bean instanceof AopInfrastructureBean) {
        // Ignore AOP infrastructure such as scoped proxies.
        return bean;
    }
    if (bean instanceof Advised) {
        Advised advised = (Advised) bean;
        if (!advised.isFrozen() && isEligible(AopUtils.getTargetClass(bean))) {
            // Add our local Advisor to the existing proxy's Advisor chain...
            if (this.beforeExistingAdvisors) {
                advised.addAdvisor(0, this.advisor);
            }
            else {
                advised.addAdvisor(this.advisor);
            }
            return bean;
        }
    }
    if (isEligible(bean, beanName)) {
        ProxyFactory proxyFactory = prepareProxyFactory(bean, beanName);
        if (!proxyFactory.isProxyTargetClass()) {
            evaluateProxyInterfaces(bean.getClass(), proxyFactory);
        }
        proxyFactory.addAdvisor(this.advisor);
        customizeProxyFactory(proxyFactory);
        return proxyFactory.getProxy(getProxyClassLoader());
    }
    // No proxy needed.
    return bean;
}

@Configuration
public class MyAsyncConfigurer extends AsyncConfigurerSupport {
    private static Logger LOGGER = LoggerFactory.getLogger(MyAsyncConfigurer.class);
    @Override
    public Executor getAsyncExecutor() {
        ThreadPoolTaskExecutor taskExecutor = new ThreadPoolTaskExecutor();
        taskExecutor.setCorePoolSize(2);
        taskExecutor.setMaxPoolSize(4);
        taskExecutor.setQueueCapacity(10);
        taskExecutor.setRejectedExecutionHandler((runnable, executor) -> LOGGER.error("异步线程池拒绝任务..." + runnable));
        taskExecutor.setThreadFactory(new MyAsyncThreadFactory());
        taskExecutor.initialize();
        return taskExecutor;
    }
    static class MyAsyncThreadFactory implements ThreadFactory {
        private static final AtomicInteger poolNumber = new AtomicInteger(1);
        private final ThreadGroup group;
        private final AtomicInteger threadNumber = new AtomicInteger(1);
        private final String namePrefix;
        MyAsyncThreadFactory() {
            SecurityManager s = System.getSecurityManager();
            group = (s != null) ? s.getThreadGroup() :
                    Thread.currentThread().getThreadGroup();
            namePrefix = "myasync-pool-" +
                    poolNumber.getAndIncrement() +
                    "-thread-";
        }
        @Override
        public Thread newThread(Runnable r) {
            Thread t = new Thread(group, r,
                    namePrefix + threadNumber.getAndIncrement(),
                    0);
            if (t.isDaemon())
                t.setDaemon(false);
            if (t.getPriority() != Thread.NORM_PRIORITY)
                t.setPriority(Thread.NORM_PRIORITY);
            return t;
        }
    }
}

@Component
public class MyAsyncTask {
    private static Logger LOGGER = LoggerFactory.getLogger(MyAsyncConfigurer.class);
    /**
     * Lazy 功能
     *
     * @see DefaultListableBeanFactory#resolveDependency(DependencyDescriptor, String, Set, TypeConverter)
     * <p>
     * Spring Bean创建-解决依赖 参考链接：https://blog.csdn.net/finalcola/article/details/81537380
     */
    @Lazy
    @Autowired
    private MyInnerAsyncTask myInnerAsyncTask;
    @Autowired
    private AsyncWrapped asyncWrapped;
    @Async
    public void async() {
        LOGGER.error("async");
    }
    public void asyncInner() {
        myInnerAsyncTask.async();
    }
    public void asyncWrapped() {
        asyncWrapped.asyncProcess(() -> LOGGER.error("async wrapped"), null, null);
    }
    public void asyncWrappedWithRetry() {
        Retry retry = new Retry(2, 1000);
        asyncWrapped.asyncProcess(() -> {
            throw new RuntimeException("async wrapped with retry");
        }, null, retry);
    }
    public void asyncWrappedWithRetry2() {
        try {
            asyncWrapped.asyncProcess(() -> {
                throw new RuntimeException("async wrapped with retry2");
            });
        } catch (Exception e) {
            LOGGER.error("异步调用异常...", e);
        }
    }
    private class MyInnerAsyncTask {
        @Async
        public void async() {
            LOGGER.error("async inner");
        }
    }
    @Configuration
    public static class MyAsyncTaskConfiguration {
        @Bean
        public MyInnerAsyncTask myInnerAsyncTask(MyAsyncTask myAsyncTask) {
            return myAsyncTask.new MyInnerAsyncTask();
        }
    }
}

@Component
public class AsyncWrapped {
    protected static Logger LOGGER = LoggerFactory.getLogger(AsyncWrapped.class);
    @Async
    public void asyncProcess(Runnable runnable, Callback callback, Retry retry) {
        try {
            if (retry == null) {
                retry = new Retry(1);
            }
            retry.execute(ctx -> {
                runnable.run();
                return null;
            }, ctx -> {
                if (callback != null) {
                    callback.call();
                }
                return null;
            });
        } catch (Exception e) {
            LOGGER.error("异步调用异常...", e);
        }
    }
    @Async
    @Retryable(value = Exception.class, maxAttempts = 3, backoff = @Backoff(delay = 2000, multiplier = 1.5))
    public void asyncProcess(Runnable runnable) throws Exception {
        System.out.println("重试中...");
        runnable.run();
    }
    @FunctionalInterface
    public interface Runnable {
        void run() throws Exception;
    }
    @FunctionalInterface
    public interface Callback {
        void call();
    }
}

@Override
public Object applyBeanPostProcessorsAfterInitialization(Object existingBean, String beanName)
        throws BeansException {
    Object result = existingBean;
    for (BeanPostProcessor processor : getBeanPostProcessors()) {
        Object current = processor.postProcessAfterInitialization(result, beanName);
        if (current == null) {
            return result;
        }
        result = current;
    }
    return result;
}

//如果是advised
if (bean instanceof Advised) {
    Advised advised = (Advised) bean;
    if (!advised.isFrozen() && isEligible(AopUtils.getTargetClass(bean))) {
        // Add our local Advisor to the existing proxy's Advisor chain...
        if (this.beforeExistingAdvisors) {
            advised.addAdvisor(0, this.advisor);
        }
        else {
            advised.addAdvisor(this.advisor);
        }
        return bean;
    }
}
//这里的逻辑不会执行了
if (isEligible(bean, beanName)) {
    ProxyFactory proxyFactory = prepareProxyFactory(bean, beanName);
    if (!proxyFactory.isProxyTargetClass()) {
        evaluateProxyInterfaces(bean.getClass(), proxyFactory);
    }
    proxyFactory.addAdvisor(this.advisor);
    customizeProxyFactory(proxyFactory);
    return proxyFactory.getProxy(getProxyClassLoader());
}

......
//设置需要代理的接口
enhancer.setInterfaces(AopProxyUtils.completeProxiedInterfaces(this.advised));
......
//获取callbacks
Callback[] callbacks = getCallbacks(rootClass);
......
//设置callback filter
enhancer.setCallbackFilter(new ProxyCallbackFilter(
        this.advised.getConfigurationOnlyCopy(), this.fixedInterceptorMap, this.fixedInterceptorOffset));
.....

......
if (addSpringProxy) {
    proxiedInterfaces[index] = SpringProxy.class;
    index++;
}
if (addAdvised) {
    proxiedInterfaces[index] = Advised.class;
    index++;
}
if (addDecoratingProxy) {
    proxiedInterfaces[index] = DecoratingProxy.class;
}
......

Callback[] mainCallbacks = new Callback[] {
            aopInterceptor,  // for normal advice
            targetInterceptor,  // invoke target without considering advice, if optimized
            new SerializableNoOp(),  // no override for methods mapped to this
            targetDispatcher, this.advisedDispatcher,
            new EqualsInterceptor(this.advised),
            new HashCodeInterceptor(this.advised)
    };

......
if (!this.advised.isOpaque() && method.getDeclaringClass().isInterface() &&
            method.getDeclaringClass().isAssignableFrom(Advised.class)) {
        if (logger.isTraceEnabled()) {
            logger.trace("Method is declared on Advised interface: " + method);
        }
        return DISPATCH_ADVISED;
    }
......

//Dispatcher for any methods declared on the Advised class.
private static class AdvisedDispatcher implements Dispatcher, Serializable {
    private final AdvisedSupport advised;
    public AdvisedDispatcher(AdvisedSupport advised) {
        this.advised = advised;
    }
    @Override
    public Object loadObject() throws Exception {
        return this.advised;
    }
}

AsyncAnnotationBeanPostProcessor#postProcessAfterInitialization（）
//如果是advised
if (bean instanceof Advised) {
    Advised advised = (Advised) bean;
    if (!advised.isFrozen() && isEligible(AopUtils.getTargetClass(bean))) {
        // Add our local Advisor to the existing proxy's Advisor chain...
        if (this.beforeExistingAdvisors) {
            advised.addAdvisor(0, this.advisor);
        }
        else {
            advised.addAdvisor(this.advisor);
        }
        return bean;
    }
}

//spring aop cglib代理对象
public class XXXX$$EnhancerBySpringCGLIB$$8f47b115 implements Advised {
    private org.springframework.cglib.proxy.Dispatcher advisedDispatcher;//AdvisedDispatcher实例
    ......
    @Override
    public void addAdvisor(int pos, Advisor advisor) throws AopConfigException() {
        advisedDispatcher.loadObject().addAdvisor(pos, advisor);
    }
    ......
}