JarCastingDDD Base
Domain Driven Design base package for Java.
How to use it in Java?
Please refer https://jitpack.io/#linux-china/ddd-base/1.1.1
Features
- Annotations
- Base classes for entity, domain event etc
- Domain event: follow CloudEvents specification and CloudEvent convert support
- DDD Reactive: https://www.reactive-streams.org/
Components
- Data: Entity, VO and Aggregate
- Behaviour: Repository, Service, Factory and Specification
- Event: Follow CloudEvents spec
- Infrastructure
- CQRS interfaces for command & query
Reactive
DDD + Reactive(RSocket) to make context map easy.
Code Structure
Please visit src/test/java for code structure
If you use Kotlin to develop application, the structure will be different, please add entity, vo and repository in the same kt file.
Events
Please extend DomainEvent or DomainEventBuilder, then use ApplicationEventPublisher to publish the event. please refer https://spring.io/blog/2015/02/11/better-application-events-in-spring-framework-4-2
Attention: Spring framework 5.2 will add reactive support: https://github.com/spring-projects/spring-framework/issues/21831
Event extensions(JavaScript Object):
- Distributed Tracing extension(traceparent, tracestate): embeds context from Distributed Tracing so that distributed systems can include traces that span an event-driven system.
- Dataref(dataref): reference another location where this information is stored
- Partitioning(partitionkey): This extension defines an attribute for use by message brokers and their clients that support partitioning of events, typically for the purpose of scaling.
- Sequence(sequence): describe the position of an event in the ordered sequence of events produced by a unique event source
- Sampling(sampledrate): Sampling
- Multi-tenant(tenantId): Multi-tenant system support
CloudEvents JSONSchema: https://github.com/cloudevents/spec/blob/v0.3/spec.json
How to create event class
- Extend CloudEvent class:
public class LoginEvent extends CloudEvent<String> {
public LoginEvent(String email, String ip) {
setData(email);
setContentType("text/plain");
setExtension("ip", ip);
}
}
- Create an event directly
CloudEvent<String> loginEvent = new CloudEvent<String>("text/plain", "[email protected]");
- Event Builder or reactive processor
CloudEvent<String> loginEvent = CloudEventBuilder.<String>newInstance().contentType("text/plain").data("[email protected]").build();
ObjectMapper
- ObjectMapper creation
ObjectMapper objectMapper = new ObjectMapper();
objectMapper.setSerializationInclusion(JsonInclude.Include.NON_NULL);
objectMapper.enable(SerializationFeature.INDENT_OUTPUT);
- write as String
objectMapper.writeValueAsString(loginEvent);
- read from json text
objectMapper.readValue(jsonText, new TypeReference<CloudEvent<String>>() {});
References
- CloudEvents Specification: https://github.com/cloudevents/spec/blob/master/spec.md
- Reactive Streams: http://www.reactive-streams.org/
- DDD Reference: https://domainlanguage.com/wp-content/uploads/2016/05/DDD_Reference_2015-03.pdf
- ddd-4-java: Base classes for Domain Driven Design with Java https://github.com/fuinorg/ddd-4-java
- jMolecules – Architectural abstractions for Java with DDD concepts https://github.com/xmolecules/jmolecules
- Domain-Driven Design Crew: https://github.com/ddd-crew
- What is Event Sourcing? https://www.eventstore.com/blog/what-is-event-sourcing
- Event Sourcing and CQRS: https://www.eventstore.com/blog/event-sourcing-and-cqrs
- CQRS Document: https://cqrs.files.wordpress.com/2010/11/cqrs_documents.pdf