@arjan Your example is base on ManagedExecutorService from the Java EE
Concurrency spec. That's one topic we've been wondering about : should the
@Asynchronous interceptor go to the Java EE Concurrency spec or not ? But
it looks like the spec might not be updated.
Antonio
On Sat, Jan 17, 2015 at 12:32 AM, arjan tijms <arjan.tijms(a)gmail.com> wrote:
Hi,
On Fri, Jan 16, 2015 at 10:41 PM, Jozef Hartinger <jharting(a)redhat.com>
wrote:
> Hi Arjan,
>
> I did some changes recently in Weld interceptors and this usecase now
> works smoothly. The code is not part of a release yet. See this test for a
> simple implementation of an @Async interceptor (basically the same as your
> initial attempt). Note that the chain is repeatable but at the same time it
> is not reset after dispatch to a different thread so you no longer need the
> ThreadLocal nor any other workaround.
>
That's quite a coincidence, it's indeed rather similar ;)
I wonder how it now works though, as the InvocationContext "ctx" does not
seem to be made aware that it's been dispatched to a different thread from
within the code. Does it use an internal thread local to keep state or so?
I'll also try to see what this does on OWB. Do you think this is something
that should work, or just something that Weld happens to support regardless
of the spec?
Kind regards,
Arjan
>
>
>
https://github.com/weld/core/blob/master/tests-arquillian/src/test/java/o...
>
> Jozef
>
>
> On 01/16/2015 06:17 PM, arjan tijms wrote:
>
> Hi,
>
> I'm attempting to emulate EJB's @Asynchronous in CDI using interceptors.
>
> Originally I had defined my interceptor as follows;
>
> @Interceptor
> @Asynchronous
> @Priority(APPLICATION)
> public class AsynchronousInterceptor implements Serializable {
>
> private static final long serialVersionUID = 1L;
>
> @Resource
> private ManagedExecutorService managedExecutorService;
>
> @AroundInvoke
> public Object submitAsync(InvocationContext ctx) throws Exception {
> return new FutureDelegator(managedExecutorService.submit( ()-> {
> return ctx.proceed(); } ));
> }
>
> }
>
> With FutureDelegator as follows:
>
> public class FutureDelegator implements Future<Object> {
>
> private Future<?> future;
>
> public FutureDelegator(Future<?> future) {
> this.future = future;
> }
>
> @Override
> public Object get() throws InterruptedException, ExecutionException {
> AsyncResult<?> asyncResult = (AsyncResult<?>) future.get();
> if (asyncResult == null) {
> return null;
> }
>
> return asyncResult.get();
> }
>
> @Override
> public Object get(long timeout, TimeUnit unit) throws
> InterruptedException, ExecutionException, TimeoutException {
> AsyncResult<?> asyncResult = (AsyncResult<?>)
future.get(timeout,
> unit);
> if (asyncResult == null) {
> return null;
> }
>
> return asyncResult.get();
> }
>
> @Override
> public boolean cancel(boolean mayInterruptIfRunning) {
> return future.cancel(mayInterruptIfRunning);
> }
>
> @Override
> public boolean isCancelled() {
> return future.isCancelled();
> }
> @Override
> public boolean isDone() {
> return future.isDone();
> }
>
> }
>
> This of course didn't quite work, as the InvocationContext will be
> reset after the @AroundInvoke method returns, and an infinite intercept
> loop results (on Weld).
>
> I got it to work though on Weld by using a thread local check to break
> that loop:
>
> @Interceptor
> @Asynchronous
> @Priority(PLATFORM_BEFORE)
> public class AsynchronousInterceptor implements Serializable {
>
> private static final long serialVersionUID = 1L;
>
> @Resource
> private ManagedExecutorService managedExecutorService;
>
> private static final ThreadLocal<Boolean> asyncInvocation = new
> ThreadLocal<Boolean>();
>
> @AroundInvoke
> public synchronized Object submitAsync(InvocationContext ctx) throws
> Exception {
>
> if (TRUE.equals(asyncInvocation.get())) {
> return ctx.proceed();
> }
>
> return new FutureDelegator(managedExecutorService.submit( ()-> {
> try {
> asyncInvocation.set(TRUE);
> return ctx.proceed();
> } finally {
> asyncInvocation.remove();
> }
> }));
> }
>
> }
>
> But I've got a feeling this works just by chance and not because the
> workaround is so clever.
>
> What do you guys think, what would be the best way to support this with
> the current CDI version? Or would CDI/Interceptors need something like
> Servlet's async support, where the InvocationContext is put into async mode
> whereafter it "simply" allows an other thread to continue processing on
it?
>
> Kind regards,
> Arjan Tijms
>
>
>
>
>
>
>
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--
Antonio Goncalves
Software architect, Java Champion and Pluralsight author
Web site <