Async (Spring Framework 4.3.30.RELEASE API)

```
@Target({METHOD,TYPE})
@Retention(RUNTIME)
@Documented
public @interface Async
```
Annotation that marks a method as a candidate for asynchronous execution. Can also be used at the type level, in which case all of the type's methods are considered as asynchronous.
In terms of target method signatures, any parameter types are supported. However, the return type is constrained to either void or Future. In the latter case, you may declare the more specific ListenableFuture or CompletableFuture types which allow for richer interaction with the asynchronous task and for immediate composition with further processing steps.
A Future handle returned from the proxy will be an actual asynchronous Future that can be used to track the result of the asynchronous method execution. However, since the target method needs to implement the same signature, it will have to return a temporary Future handle that just passes a value through: e.g. Spring's AsyncResult, EJB 3.1's javax.ejb.AsyncResult, or CompletableFuture.completedFuture(Object).
Since:
3.0
Author:
Juergen Hoeller, Chris Beams
See Also:
AnnotationAsyncExecutionInterceptor, AsyncAnnotationAdvisor

- Optional Element Summary
  Optional Elements
  Modifier and Type Optional Element Description
  String value
  A qualifier value for the specified asynchronous operation(s).

- Element Detail
  - value
```
String value
```
    A qualifier value for the specified asynchronous operation(s).
    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 Executor or TaskExecutor bean definition.
    When specified on a class level @Async annotation, indicates that the given executor should be used for all methods within the class. Method level use of Async#value always overrides any value set at the class level.
    Since:
    3.1.2
    Default:
    ""