如题，不知道这个注解里的参数是干什么用的
public @interface Async {
/**
* A qualifier value for the specified asynchronous operation(s).
* <p>May be used to determine the target executor to be used when executing this
* method, matching the qualifier value (or the bean name) of a specific
* {@link java.util.concurrent.Executor Executor} or
* {@link org.springframework.core.task.TaskExecutor TaskExecutor}
* bean definition.
* <p>When specified on a class level {@code @Async} annotation, indicates that the
* given executor should be used for all methods within the class. Method level use
* of {@code Async#value} always overrides any value set at the class level.
* @since 3.1.2
*/
String value() default "";
}
