I feel stupid, but alas. If I have a REST endpoint and a query that returns a list of String, the code would look like this:
@GetMapping
public CompletableFuture<List<String>> list() {
return queryGateway.query(new GetActiveRosterDates(), ResponseTypes.multipleInstancesOf(String.class));
}
But I’ve changed the key of the aggregate to LocalDate, so I’m getting a list of those, not String. And apparently those cannot be returned.
@GetMapping
public CompletableFuture<List<LocalDate>> list() {
return queryGateway.query(new GetActiveRosterDates(), ResponseTypes.multipleInstancesOf(LocalDate.class));
}
Retrieved response [class java.util.ArrayList] is not convertible to a List of the expected response type [class java.time.LocalDate]
The response seems to need to return List of String, so we need to post process the query’s result. Since a toString can be pretty synchronous I’d expect this to work:
private List<LocalDate> activeRosterDates = new ArrayList<>();
@QueryHandler
public List<LocalDate> query(GetActiveRosterDates query) {
return activeRosterDates;
}
public record GetActiveRosterDates() {}
I am assuming that you’re using the JacksonSerializer, @tbee.
If that’s the case, then I’d like to ask you to enable default typing on the JacksonSerializer (as is described here in the Reference Guide).
The problem you’re (I assume) facing is that the LocalDate serializes to a format that loses the knowledge it used to be a LocalDate. This isn’t an issue for singular objects, but when those are dropped in a collection, you might face problems.
Makes sense. However, if you’re using the spring based setup (like I am), when trying to configure the JacksonSerializer using spring @Configuration there is conflict with Axon’s configuration.
Parameter 0 of method messageSerializer in org.axonframework.springboot.autoconfig.AxonAutoConfiguration required a single bean, but 2 were found:
- defaultSerializer: defined by method 'defaultSerializer' in class path resource [nl/softworks/selfroster/Configuration.class]
- eventSerializer: defined by method 'eventSerializer' in class path resource [org/axonframework/springboot/autoconfig/AxonAutoConfiguration.class]
Alternatively using the Axon configuration class seems not to be picked up; there is nothing marking that class as configuration? At least the method I used for setting that up was never called.
So that is why I reverted to application.properties. However, there does not seem to be a property for defining “default typing” in that way, so I had dug deeper and found that “NON_CONCRETE_AND_ARRAYS” was set for DefaultTyping. But that cannot be set via that properties file, it seems. Allowed Jackson values in the property file are: