@Import(AsyncConfigurationSelector.class)
public @interface EnableAsync {
 
    Class<? extends Annotation> annotation() default Annotation.class;
 
    boolean proxyTargetClass() default false;
 
    AdviceMode mode() default AdviceMode.PROXY;
 
    int order() default Ordered.LOWEST_PRECEDENCE;
}

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;
    }
}

public void setImportMetadata(AnnotationMetadata importMetadata) {
	this.enableAsync = AnnotationAttributes.fromMap(
			importMetadata.getAnnotationAttributes(EnableAsync.class.getName(), false));
	if (this.enableAsync == null) {
		throw new IllegalArgumentException(
				"@EnableAsync is not present on importing class " + 
           importMetadata.getClassName());
	}
}

@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;
}

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;
}

public AsyncAnnotationAdvisor(@Nullable Supplier<Executor> executor, 
    @Nullable Supplier<AsyncUncaughtExceptionHandler> exceptionHandler) {
 
    Set<Class<? extends Annotation>> asyncAnnotationTypes = new LinkedHashSet<>(2);
    asyncAnnotationTypes.add(Async.class);
    try {
        asyncAnnotationTypes.add((Class<? extends Annotation>)
        ClassUtils.forName("javax.ejb.Asynchronous", 
        AsyncAnnotationAdvisor.class.getClassLoader()));
    } catch (ClassNotFoundException ex) {
    // If EJB 3.1 API not present, simply ignore.
    }
    this.advice = buildAdvice(executor, exceptionHandler);
    this.pointcut = buildPointcut(asyncAnnotationTypes);
}

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

protected Pointcut buildPointcut(Set<Class<? extends Annotation>> asyncAnnotationTypes) {
    ComposablePointcut result = null;
    // asyncAnnotationTypes默認(rèn)只要Async類型
    for (Class<? extends Annotation> asyncAnnotationType : asyncAnnotationTypes) {
        Pointcut cpc = new AnnotationMatchingPointcut(asyncAnnotationType, true);
        Pointcut mpc = new AnnotationMatchingPointcut(null, asyncAnnotationType, true);
        if (result == null) {
            // result肯定是null，先添加Class類型的切點(diǎn)匹配器
            result = new ComposablePointcut(cpc);
        } else {
            result.union(cpc);
        }
        // 再添加Method類型的切點(diǎn)攔截器
        result = result.union(mpc);
    }
    return (result != null ? result : Pointcut.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;
}

protected ProxyFactory prepareProxyFactory(Object bean, String beanName) {
    ProxyFactory proxyFactory = new ProxyFactory();
    proxyFactory.copyFrom(this);
    proxyFactory.setTarget(bean);
    return proxyFactory;
}

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 AsyncExecutionAspectSupport(@Nullable Executor defaultExecutor) {
	this.defaultExecutor = new SingletonSupplier<>(defaultExecutor, () -> getDefaultExecutor(this.beanFactory));
	this.exceptionHandler = SingletonSupplier.of(SimpleAsyncUncaughtExceptionHandler::new);
}

protected Executor getDefaultExecutor(@Nullable BeanFactory beanFactory) {
	if (beanFactory != null) {
		try {
			// Search for TaskExecutor bean... not plain Executor since that would
			// match with ScheduledExecutorService as well, which is unusable for
			// our purposes here. TaskExecutor is more clearly designed for it.
			return beanFactory.getBean(TaskExecutor.class);
		}
		catch (NoUniqueBeanDefinitionException ex) {
			logger.debug("Could not find unique TaskExecutor bean", ex);
			try {
				return beanFactory.getBean(DEFAULT_TASK_EXECUTOR_BEAN_NAME, Executor.class);
			}
			catch (NoSuchBeanDefinitionException ex2) {
				if (logger.isInfoEnabled()) {
					logger.info("More than one TaskExecutor bean found within the context, and none is named " +
							"'taskExecutor'. Mark one of them as primary or name it 'taskExecutor' (possibly " +
							"as an alias) in order to use it for async processing: " + ex.getBeanNamesFound());
				}
			}
		}
		catch (NoSuchBeanDefinitionException ex) {
			logger.debug("Could not find default TaskExecutor bean", ex);
			try {
				return beanFactory.getBean(DEFAULT_TASK_EXECUTOR_BEAN_NAME, Executor.class);
			}
			catch (NoSuchBeanDefinitionException ex2) {
				logger.info("No task executor bean found for async processing: " +
						"no bean of type TaskExecutor and no bean named 'taskExecutor' either");
			}
			// Giving up -> either using local default executor or none at all...
		}
	}
	return null;
}

protected AsyncTaskExecutor determineAsyncExecutor(Method method) {
    AsyncTaskExecutor executor = this.executors.get(method);
    if (executor == null) {
        Executor targetExecutor;
        String qualifier = getExecutorQualifier(method);
        if (StringUtils.hasLength(qualifier)) {
            targetExecutor = findQualifiedExecutor(this.beanFactory, qualifier);
        } else {
            targetExecutor = this.defaultExecutor.get();
        }
        if (targetExecutor == null) {
            return null;
        }
        executor = (targetExecutor instanceof AsyncListenableTaskExecutor ?
            (AsyncListenableTaskExecutor) targetExecutor : new 
                 TaskExecutorAdapter(targetExecutor));
        this.executors.put(method, executor);
    }
    return executor;
}

protected String getExecutorQualifier(Method method) {
    // Maintainer's note: changes made here should also be made in
    // AnnotationAsyncExecutionAspect#getExecutorQualifier
    Async async = AnnotatedElementUtils.findMergedAnnotation(method, Async.class);
    if (async == null) {
        async = AnnotatedElementUtils.findMergedAnnotation(method.getDeclaringClass(), Async.class);
    }
    return (async != null ? async.value() : null);
}

protected Executor findQualifiedExecutor(@Nullable BeanFactory beanFactory, String qualifier) {
    if (beanFactory == null) {
        throw new IllegalStateException("BeanFactory must be set on " + getClass().getSimpleName() +
					" to access qualified executor '" + qualifier + "'");
    }
    return BeanFactoryAnnotationUtils.qualifiedBeanOfType(beanFactory, Executor.class, qualifier);
}

protected Object doSubmit(Callable<Object> task, AsyncTaskExecutor executor, 
    Class<?> returnType) {
    
    if (completableFuturePresent) {
        Future<Object> result = AsyncExecutionAspectSupport.CompletableFutureDelegate
        .processCompletableFuture(returnType, task, executor);
        if (result != null) {
            return result;
        }
    }
 
    if (ListenableFuture.class.isAssignableFrom(returnType)) {
        return ((AsyncListenableTaskExecutor)executor).submitListenable(task);
    } else if (Future.class.isAssignableFrom(returnType)) {
        return executor.submit(task);
    } else {
        executor.submit(task);
        return null;
    }
}

@Override
public <T> Future<T> submit(Callable<T> task) {
    FutureTask<T> future = new FutureTask<>(task);
    execute(future, TIMEOUT_INDEFINITE);
    return future;
}

@Override
public void execute(Runnable task, long startTimeout) {
    Assert.notNull(task, "Runnable must not be null");
    Runnable taskToUse = (this.taskDecorator != null ? this.taskDecorator.decorate(task) : task);
    if (isThrottleActive() && startTimeout > TIMEOUT_IMMEDIATE) {
        this.concurrencyThrottle.beforeAccess();
        doExecute(new ConcurrencyThrottlingRunnable(taskToUse));
    } else {
        doExecute(taskToUse);
    }
}

protected void doExecute(Runnable task) {
    Thread thread = (this.threadFactory != null ? this.threadFactory.newThread(task) 
        : createThread(task));
    thread.start();
}

public Thread createThread(Runnable runnable) {
    Thread thread = new Thread(getThreadGroup(), runnable, nextThreadName());
    thread.setPriority(getThreadPriority());
    thread.setDaemon(isDaemon());
    return thread;
}