Implementing Snapshot in AXON 3.0 : Aggregate Type is unknown in this snapShotter - spring

Question

I'm still new to the axon frame work.
I'm trying to implement snapshotting using mongodb in my application and I keep on getting an error saying
"AbstractSnapshotter : An attempt to create and store a snapshot resulted in an exception. Exception summary: Aggregate Type is unknown in this snapshotter: com.myworklife.contacts.domain.contact.Contact"
This is a part of my java config file.
#Bean
public AggregateSnapshotter snapShotter(EventStore eventStore, AggregateFactory<Contact> contactAggregateFactory) {
return new AggregateSnapshotter(eventStore);
}
#Bean
public SnapshotTriggerDefinition snapshotTriggerDefinition(Snapshotter snapShotter) throws Exception {
return new EventCountSnapshotTriggerDefinition(snapShotter, 1);
}
#Bean
public EventStore eventStore(EventStorageEngine eventStorageEngine) {
return new EmbeddedEventStore(eventStorageEngine);
}
#Bean
public Repository<Contact> contactAggregateRepository(EventStore eventStore, SnapshotTriggerDefinition snapshotTriggerDefinition) {
return new ContactRepository(eventStore, snapshotTriggerDefinition);
}
And my repository.
#Repository("ContactRepository")
public class ContactRepository extends EventSourcingRepository<Contact> {
#Autowired
public ContactRepository(EventStore eventStore, SnapshotTriggerDefinition snapshotTriggerDefinition) {
super(Contact.class, eventStore, snapshotTriggerDefinition);
}
public Contact findContact(ContactId contactId) {
return load(contactId.toString()).getWrappedAggregate().getAggregateRoot();
}
}
My aggregate.
#Aggregate(repository="contactAggregateRepository")
public class Contact {
#AggregateIdentifier
private ContactId id;
private String name;
private String mobileNumber;
public Contact() {
// do nothing, Axon requires default constructor
}
#CommandHandler
public Contact(CreateContactCommand createContactCommand) {
apply(new ContactHasBeenCreatedEvent(createContactCommand.getContactId(), createContactCommand.getName(),
createContactCommand.getMobileNumber()));
}
}
Is there something I'm doing wrong?
since I'm getting an error saying "An attempt to create and store a snapshot resulted in an exception. Exception summary: Aggregate Type is unknown in this snapshotter: com.myworklife.contacts.domain.contact.Contact"
Any help will be highly appreciated.
Thanks,
Pat

Answer 1

You need to add the contactAggregateFactory to the constructor of the AggregateSnapshotter in the snapShotter bean:
#Bean
public AggregateSnapshotter snapShotter(EventStore eventStore, AggregateFactory<Contact> contactAggregateFactory) {
return new AggregateSnapshotter(eventStore, contactAggregateFactory);
}

Answer 2

1.depencity jar
<dependency>
<groupId>org.axonframework</groupId>
<artifactId>axon-spring-boot-autoconfigure</artifactId>
<version>${axon.version}</version>
</dependency>
2.At first,you should config your application.ymp or bootstrap.yml,like this:spring:
data:
mongodb:
host: localhost
port: 27017
database: axonframework
events: domainevents
snapshots: snapshotevents
3.config your mongoDB:
#Bean(name = "axonMongoTemplate")
public MongoTemplate axonMongoTemplate() {
MongoTemplate template = new DefaultMongoTemplate(mongoClient(), mongoDbName, eventsCollectionName, snapshotCollectionName);
return template;
}
#Bean
public MongoClient mongoClient(){
MongoFactory mongoFactory = new MongoFactory();
mongoFactory.setMongoAddresses(Arrays.asList(new ServerAddress(mongoHost)));
return mongoFactory.createMongo();
}
#Bean
public EventStorageEngine eventStorageEngine(Serializer serializer){
return new MongoEventStorageEngine(
serializer,null, axonMongoTemplate(), new DocumentPerEventStorageStrategy());
4.config repository for your aggregate,for example,i config a Element Aggreaget's repository
#Configuration
public class ElementConfiguration {
#Autowired
private EventStore eventStore;
#Bean
#Scope("prototype")
public Element elementAggregate() {
return new Element();
}
#Bean
public AggregateFactory<Element> elementAggregateAggregateFactory() {
SpringPrototypeAggregateFactory<Element> aggregateFactory = new SpringPrototypeAggregateFactory<>();
aggregateFactory.setPrototypeBeanName("elementAggregate");
return aggregateFactory;
}
#Bean
public SpringAggregateSnapshotterFactoryBean springAggregateSnapshotterFactoryBean(){
SpringAggregateSnapshotterFactoryBean factory = new SpringAggregateSnapshotterFactoryBean();
return factory;
}
#Bean
public Repository<Element> elementAggregateRepository(Snapshotter snapshotter) {
EventCountSnapshotTriggerDefinition eventCountSnapshotTriggerDefinition = new EventCountSnapshotTriggerDefinition(snapshotter, 3);
EventSourcingRepository<Element> repository = new EventSourcingRepository<Element>(
elementAggregateAggregateFactory(),
eventStore,
eventCountSnapshotTriggerDefinition
);
return repository;
}
5.enjoy

Answer 3

If you're using Axon 3.3 and SpringBoot 2, this is how we did it in this project:
#Configuration
public class SnapshotConfiguration {
#Bean
public SpringAggregateSnapshotter snapshotter(ParameterResolverFactory parameterResolverFactory,
EventStore eventStore,
TransactionManager transactionManager) {
// https://docs.axoniq.io/reference-guide/v/3.3/part-iii-infrastructure-components/repository-and-event-store#snapshotting
// (...) By default, snapshots are created in the thread that calls the scheduleSnapshot() method, which is generally not recommended for production (...)
Executor executor = Executors.newSingleThreadExecutor();
return new SpringAggregateSnapshotter(eventStore, parameterResolverFactory, executor, transactionManager);
}
#Bean
public EventCountSnapshotTriggerDefinition snapshotTrigger(SpringAggregateSnapshotter snapshotter) {
int snapshotThreshold = 42;
return new EventCountSnapshotTriggerDefinition(snapshotter, snapshotThreshold);
}
}
And if you need the EventStore configuration:
#Configuration
public class AxonMongoEventStoreConfiguration {
#Bean
public MongoClient axonMongoClient(MongoClientURI axonMongoClientUri) {
return new MongoClient(axonMongoClientUri);
}
#Bean
public MongoClientURI axonMongoClientUri() {
return new MongoClientURI("mongodb://host:port/database");
}
#Bean
#Primary
public EventStorageEngine eventStore(MongoClient axonMongoClient, MongoClientURI axonMongoClientUri) {
DefaultMongoTemplate mongoTemplate = new DefaultMongoTemplate(axonMongoClient, axonMongoClientUri.getDatabase());
return new MongoEventStorageEngine(mongoTemplate);
}
}