Update warning log messages for SimpleAsyncTaskManager to take into account virtual thread mode

[rstoyanchev]

Currently we log this in WebAsyncManager and similar warning exists in ReactiveTypeHandler too:

!!!
An Executor is required to handle java.util.concurrent.Callable return values.
Please, configure a TaskExecutor in the MVC config under "async support".
The SimpleAsyncTaskExecutor currently in use is not suitable under load.
-------------------------------
Request URI: '/'
!!!

This should not be logged if using virtual threads.

[wilkinsona]

Can a SimpleAsyncTaskExecutor with virtual threads enabled also be taken into account? It's what Boot auto-configures when virtual threads are enabled.

[quaff]

This should not be logged if the executor is VirtualThreadTaskExecutor.

VirtualThreadTaskExecutor is AsyncTaskExecutor, neither SimpleAsyncTaskExecutor nor SyncTaskExecutor.

spring-framework/spring-core/src/main/java/org/springframework/core/task/VirtualThreadTaskExecutor.java

Line 32 in 0d8a843

public class VirtualThreadTaskExecutor implements AsyncTaskExecutor {

spring-framework/spring-web/src/main/java/org/springframework/web/context/request/async/WebAsyncManager.java

Line 365 in 0d8a843

(executor instanceof SimpleAsyncTaskExecutor || executor instanceof SyncTaskExecutor)) {

[rstoyanchev]

Indeed, VirtualThreadTaskExecutor is not relevant here, and we're checking for SimpleAsyncTaskExecutor. There is similar check and warning in ReactiveTypeHandler too. I've updated the title and description to reflect that.