Class not found when trying to return List from consumeEvent in Quarkus - vert.x

Question

When I try to return a Uni with a typed java.util.List in Quarkus in dev mode, i get a ClassNotFound exception. I have read about Quarkus using different class loaders in different profiles, but I don't see that I do anything fancy.
Here's the sender
#Query("offers")
public Uni<List<OfferResponse>> getOffers(#PathParam("category") Integer categoryId) {
OfferRequest event = new OfferRequest();
event.setCategoryId(categoryId);
Uni<List<OfferResponse>> offers = bus.<List<OfferResponse>>request(OfferRequest.ADDRESS, event).onItem().transform(Message::body);
return offers;
}
And here's the consumer
#ConsumeEvent(OfferRequest.ADDRESS)
public Uni<List<OfferResponse>> onOfferQuery(OfferRequest request) {
List<KelkooOffer> offers = getOffers(request.getCategoryId());
List<OfferResponse> responses = new ArrayList<OfferResponse>();
for (KelkooOffer offer : offers) {
responses.add(offer.getEventResponse());
}
return Uni.createFrom().item(responses);
}
The bean I'm trying to return is just a POJO
and the error message
2021-08-18 11:11:16,186 ERROR [io.qua.run.Application] (Quarkus Main Thread) Failed to start application (with profile dev): java.lang.ClassNotFoundException: java.util.List<se.bryderi.events.OfferResponse>
at java.base/jdk.internal.loader.BuiltinClassLoader.loadClass(BuiltinClassLoader.java:581)
at java.base/jdk.internal.loader.ClassLoaders$AppClassLoader.loadClass(ClassLoaders.java:178)
at java.base/java.lang.ClassLoader.loadClass(ClassLoader.java:522)
at io.quarkus.bootstrap.classloading.QuarkusClassLoader.loadClass(QuarkusClassLoader.java:414)
at io.quarkus.bootstrap.classloading.QuarkusClassLoader.loadClass(QuarkusClassLoader.java:405)
at io.quarkus.bootstrap.classloading.QuarkusClassLoader.loadClass(QuarkusClassLoader.java:414)
at io.quarkus.bootstrap.classloading.QuarkusClassLoader.loadClass(QuarkusClassLoader.java:405)
at java.base/java.lang.Class.forName0(Native Method)
at java.base/java.lang.Class.forName(Class.java:398)
at io.quarkus.deployment.steps.VertxProcessor$build609260703.deploy_0(VertxProcessor$build609260703.zig:142)
at io.quarkus.deployment.steps.VertxProcessor$build609260703.deploy(VertxProcessor$build609260703.zig:40)
at io.quarkus.runner.ApplicationImpl.doStart(ApplicationImpl.zig:784)
at io.quarkus.runtime.Application.start(Application.java:101)
at io.quarkus.runtime.ApplicationLifecycleManager.run(ApplicationLifecycleManager.java:101)
at io.quarkus.runtime.Quarkus.run(Quarkus.java:66)
at io.quarkus.runtime.Quarkus.run(Quarkus.java:42)
at io.quarkus.runtime.Quarkus.run(Quarkus.java:119)
at io.quarkus.runner.GeneratedMain.main(GeneratedMain.zig:29)
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.base/java.lang.reflect.Method.invoke(Method.java:566)
at io.quarkus.runner.bootstrap.StartupActionImpl$1.run(StartupActionImpl.java:98)
at java.base/java.lang.Thread.run(Thread.java:829)
I get the same result if I run the dev profile or if I run the packaged fast-jar.
Happy for any hint that will point me in the right direction

Answer 1

There is a limitation of the Vert.x EventBus which prevents to encode/decode lists or sets directly.
You could create a wrapper for your OfferResponse list:
import java.util.AbstractList;
import java.util.List;
public class OfferResponseList extends AbstractList<OfferResponse> {
private List<OfferResponse> wrapped;
private OfferResponseList(List<OfferResponse> wrapped) {
this.wrapped = wrapped;
}
public static OfferResponseList wrap(List<OfferResponse> list) {
return new OfferResponseList(list);
}
#Override
public OfferResponse get(int index) {
return wrapped.get(index);
}
#Override
public int size() {
return wrapped.size();
}
}
Then transform your consumer to:
#ConsumeEvent(OfferRequest.ADDRESS)
public Uni<OfferResponseList> onOfferQuery(OfferRequest request) {
List<KelkooOffer> offers = getOffers(request.getCategoryId());
List<OfferResponse> responses = new ArrayList<OfferResponse>();
for (KelkooOffer offer : offers) {
responses.add(offer.getEventResponse());
}
// Notice the call to OfferResponseList.wrap here
return Uni.createFrom().item(OfferResponseList.wrap(responses));
}
That's it. Quarkus will register a codec for OfferResponseList automatically.
On the client side, you do not need to change your code:
#Query("offers")
public Uni<List<OfferResponse>> getOffers(#PathParam("category") Integer categoryId) {
OfferRequest event = new OfferRequest();
event.setCategoryId(categoryId);
// You can use Uni<List<OfferResponse>> or Uni<OfferResponseList>
Uni<List<OfferResponse>> offers = bus.<List<OfferResponse>>request(OfferRequest.ADDRESS, event).onItem().transform(Message::body);
return offers;
}