Method Annotated with #EventHandler is not getting triggered in Axon Based Spring Boot Microservice - spring-boot

Question

The event is getting stored in the event store but not getting persisted in the Entity table.
My Controller method
#PostMapping("/saveProduct")
public ResponseEntity<Void> productCreator(#RequestBody CreateProductModel createProductModel){
CreateProductCommand createProductCommand = CreateProductCommand.builder().
productId(UUID.randomUUID().toString()).
title(createProductModel.getTitle()).
description(createProductModel.getDescription()).
price(createProductModel.getPrice()).
discountPercentage(createProductModel.getDiscountPercentage()).
available(createProductModel.isAvailable()).build();
try {
commandGateway.sendAndWait(createProductCommand);
}catch(Exception e) {
e.printStackTrace();
return new ResponseEntity<>(HttpStatus.BAD_REQUEST);
}
return new ResponseEntity<>(HttpStatus.OK);
}
Aggregate Class
#Aggregate
public class ProductAggregate {
#AggregateIdentifier
private String productId;
private String title;
private String description;
private int price;
private short discountPercentage;
private boolean available;
public ProductAggregate() {
//leave it blank always
}
#CommandHandler
public ProductAggregate(CreateProductCommand createProductCommand) {
ProductCreatedEvent productCreatedEvent = new ProductCreatedEvent();
BeanUtils.copyProperties(createProductCommand, productCreatedEvent);
AggregateLifecycle.apply(productCreatedEvent);
}
#EventSourcingHandler
public void on(ProductCreatedEvent productCreatedEvent) {
this.productId = productCreatedEvent.getProductId();
this.title = productCreatedEvent.getTitle();
this.description = productCreatedEvent.getDescription();
this.price = productCreatedEvent.getPrice();
this.discountPercentage = productCreatedEvent.getDiscountPercentage();
this.available = productCreatedEvent.isAvailable();
}
}
But this below class's method public void on(ProductCreatedEvent productCreatedEvent) is not getting called because of which the events are getting stored in event store but not getting persisted. Can someone help why this is happening?
#Service
public class ProductEventsHandler {
private final ProductRepo productRepo;
public ProductEventsHandler(ProductRepo productRepo) {
this.productRepo = productRepo;
}
#EventHandler
public void on(ProductCreatedEvent productCreatedEvent) {
//1. Create object of entity
Product product = new Product();
//2. Copy from productCreatedEvent(event) to entity
BeanUtils.copyProperties(productCreatedEvent, product);
//3. repository.save(entity);
productRepo.save(product);
}
}
Also, I am getting an exception while running the application as below :
2021-11-07 00:19:20.677 INFO 6668 --- [ main] com.netflix.discovery.DiscoveryClient : Initializing Eureka in region us-east-1
2021-11-07 00:19:20.719 INFO 6668 --- [ main] c.n.d.s.r.aws.ConfigClusterResolver : Resolving eureka endpoints via configuration
2021-11-07 00:19:20.782 WARN 6668 --- [s.CQRS.query]-0] o.a.e.TrackingEventProcessor : Error occurred. Starting retry mode.
com.thoughtworks.xstream.security.ForbiddenClassException: com.solinvictus.Products.CQRS.events.ProductCreatedEvent
at com.thoughtworks.xstream.security.NoTypePermission.allows(NoTypePermission.java:26) ~[xstream-1.4.18.jar:1.4.18]
at com.thoughtworks.xstream.mapper.SecurityMapper.realClass(SecurityMapper.java:74) ~[xstream-1.4.18.jar:1.4.18]
at com.thoughtworks.xstream.mapper.MapperWrapper.realClass(MapperWrapper.java:125) ~[xstream-1.4.18.jar:1.4.18]
at com.thoughtworks.xstream.mapper.CachingMapper.realClass(CachingMapper.java:47) ~[xstream-1.4.18.jar:1.4.18]
at org.axonframework.serialization.AbstractXStreamSerializer.classForType(AbstractXStreamSerializer.java:159) ~[axon-messaging-4.2.jar:4.2]
at org.axonframework.serialization.LazyDeserializingObject.<init>(LazyDeserializingObject.java:83) ~[axon-messaging-4.2.jar:4.2]
at org.axonframework.eventhandling.EventUtils.lambda$upcastAndDeserializeTrackedEvents$1(EventUtils.java:99) ~[axon-messaging-4.2.jar:4.2]
at java.util.stream.ReferencePipeline$3$1.accept(ReferencePipeline.java:193) ~[na:1.8.0_202]
at java.util.stream.ReferencePipeline$3$1.accept(ReferencePipeline.java:193) ~[na:1.8.0_202]
at org.axonframework.eventsourcing.eventstore.BatchingEventStorageEngine$EventStreamSpliterator.tryAdvance(BatchingEventStorageEngine.java:242) ~[axon-eventsourcing-4.2.jar:4.2]
at java.util.stream.StreamSpliterators$WrappingSpliterator.lambda$initPartialTraversalState$0(StreamSpliterators.java:294) ~[na:1.8.0_202]
at java.util.stream.StreamSpliterators$AbstractWrappingSpliterator.fillBuffer(StreamSpliterators.java:206) ~[na:1.8.0_202]
at java.util.stream.StreamSpliterators$AbstractWrappingSpliterator.doAdvance(StreamSpliterators.java:161) ~[na:1.8.0_202]
at java.util.stream.StreamSpliterators$WrappingSpliterator.tryAdvance(StreamSpliterators.java:300) ~[na:1.8.0_202]
at java.util.Spliterators$1Adapter.hasNext(Spliterators.java:681) ~[na:1.8.0_202]
at org.axonframework.eventsourcing.eventstore.EmbeddedEventStore$EventConsumer.peekPrivateStream(EmbeddedEventStore.java:397) ~[axon-eventsourcing-4.2.jar:4.2]
at org.axonframework.eventsourcing.eventstore.EmbeddedEventStore$EventConsumer.peek(EmbeddedEventStore.java:356) ~[axon-eventsourcing-4.2.jar:4.2]
at org.axonframework.eventsourcing.eventstore.EmbeddedEventStore$EventConsumer.hasNextAvailable(EmbeddedEventStore.java:333) ~[axon-eventsourcing-4.2.jar:4.2]
at org.axonframework.common.stream.BlockingStream.hasNextAvailable(BlockingStream.java:40) ~[axon-messaging-4.2.jar:4.2]
at org.axonframework.eventhandling.TrackingEventProcessor.checkSegmentCaughtUp(TrackingEventProcessor.java:464) ~[axon-messaging-4.2.jar:4.2]
at org.axonframework.eventhandling.TrackingEventProcessor.processBatch(TrackingEventProcessor.java:351) ~[axon-messaging-4.2.jar:4.2]
at org.axonframework.eventhandling.TrackingEventProcessor.processingLoop(TrackingEventProcessor.java:275) ~[axon-messaging-4.2.jar:4.2]
at org.axonframework.eventhandling.TrackingEventProcessor$TrackingSegmentWorker.run(TrackingEventProcessor.java:1071) [axon-messaging-4.2.jar:4.2]
at org.axonframework.eventhandling.TrackingEventProcessor$WorkerLauncher.run(TrackingEventProcessor.java:1183) [axon-messaging-4.2.jar:4.2]
at java.lang.Thread.run(Thread.java:748) [na:1.8.0_202]

Answer 1

You've encountered a failure in Axon's upcaster because of a ForbiddenClassException thrown by XStream.
2021-11-07 00:19:20.782 WARN 6668 --- [s.CQRS.query]-0] o.a.e.TrackingEventProcessor : Error occurred. Starting retry mode.
com.thoughtworks.xstream.security.ForbiddenClassException: com.solinvictus.Products.CQRS.events.ProductCreatedEvent
To solve this you should allow XStream for your event classes to be serialized as stated in this answer

Answer 2

There were two issues that I found in my code :
The issue was with XStream so I excluded the Xstream dependency from the axon framework and added the XStream dependency myself ().
<dependency>
<groupId>org.axonframework</groupId>
<artifactId>axon-spring-boot-starter</artifactId>
<version>4.2</version>
<exclusions>
<exclusion>
<groupId>org.axonframework</groupId>
<artifactId>axon-server-connector</artifactId>
</exclusion>
<exclusion>
<groupId>com.thoughtworks.xstream</groupId>
<artifactId>xstream</artifactId>
</exclusion>
</exclusions>
</dependency>
<dependency>
<groupId>com.thoughtworks.xstream</groupId>
<artifactId>xstream</artifactId>
<version>1.4.17</version>
</dependency>
The silly one:
I had annotated the "id" field of the entity class with #GeneratedValue and since I was populating the value using UUID that was causing the error. It was causing the error. I didn't notice this issue until I did the 1st fix(mentioned above)