Insight spring @Async 工作机制

疑问：@Async 是怎样解析的，spring如何实现注解方法的异步调用？

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0、@Async 的应用： Creating Asynchronous Methods

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1、@Async 的作用

按照惯例，annotation 是bean-post-processor处理的。处理@Async 的processor 就是在解析task:annotation-driven 配置过程中注册的，参考Insight task:annotation-driven 解析。

看看注册的AsyncAnnotationBeanPostProcessor 做了什么：

a.processor 指定属性advisor默认为AsyncAnnotationAdvisor，至此可以知道spring 异步方法支持是通过AOP 实现的!

b.哪些类会创建proxy，判断bean class是否有@Async 或者method 有@Async(see AsyncAnnotationAdvisor.pointcut)。

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2、异步方法实现：

AsyncAnnotationAdvisor.advice = new AnnotationAsyncExecutionInterceptor(executor)。

直接上AnnotationAsyncExecutionInterceptor源码：

/**
 * Intercept the given method invocation, 
 * submit the actual calling of the method to the correct task executor and return immediately to the caller.
 */
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);
    specificMethod = BridgeMethodResolver.findBridgedMethod(specificMethod);
    
    AsyncTaskExecutor executor = determineAsyncExecutor(specificMethod);
    if (executor == null) {
	    throw new IllegalStateException("No executor specified and no default executor set on AsyncExecutionInterceptor either");
    }
    // 熟悉的Executor、Future
    Future
   
    result = executor.submit(
        	new Callable