Creating Future-Proof Spring Applications with Event Sourcing

Steve Pember - Stavvy

Event Sourcing is a modern but non-trivial data model for building scalable and powerful systems. Instead of mapping a single Entity to a single row in a datastore, in an Event Sourced system we persist all changes for an Entity in an append-only journal. This design provides a wealth of benefits: a built-in Audit Trail, Time-Based reporting, powerful Error Recovery, and more. It creates flexible, scalable systems and can easily evolve to meet changing organizational demands. That is, once you have some experience with it. Event Sourcing is straightforward in concept, but it does bring additional complexity and a learning curve that can be intimidating. People coming from traditional ORM systems often wonder: how does one model relations between Entities? How is Optimistic Locking handled? What about datastore constraints?

Based on over eight years of experience with building ES systems in Spring applications, we will demonstrate the basics of Event Sourcing and some of the common patterns. We will see how simple it can be to model events with available tools like Spring Data JPA, JOOQ, and the integration between Spring and Axon. We’ll walk through sample code in an application that demonstrates many of these techniques. However, it’s also not strictly about the code; we’ll see how a process called Event Modeling can be a powerful design tool to align Subject Matter Experts, Product, and Engineering. Attendees will leave with an understanding of the basic Event Sourcing patterns, and hopefully a desire to start creating their own Journals.