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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