An Event-Storm to Event-Sourced application library
Welcome to The Domain Development Kit (DDK), a lightweight application library (not framework) designed to take you from visual collaborative Event Storming sessions to an Event-Sourced application seamlessly. This is a library for developers looking to build complex systems with a strong emphasis on separating concerns and focusing on the business logic.
The key feature of the DDK is allowing you to build an application using the building blocks shown in this diagram:
- Commands
- Aggregates
- Sagas
- External Systems (In/Out)
- Events
- Read Models
- Policies
Once you learn how to use these building blocks, you can build (almost) any backend you can imagine.
Some versions of this library has been used to build a number of applications for enterprise clients at our sister company Xolvio, and we're excited to share it with the world as the open-source counterpart to our cloud offering at XSpecs.ai.
XSpecs + DDK = Pure Joy. XSpecs provides you with a single source of truth for all your specs, and get this: You can go from Event Storming diagrams to a fully working application in a matter of hours. We've done it, and it's a beautiful thing!
Using the Domain Schema Designer in XSpecs, you can create a visual representation of your domain model. XSpecs will then generate the all the scaffolding for you to use with the DDK to build your application.
Along with the boilerplate, XSpecs also does a first pass at coding your business logic, as well as tests using AI. The result is a massive time saving that allows you to focus on decoding complex domains into artful solutions, rather than being a syntax warrior.
All changes are synced bi-directionally, so you can make changes in XSpecs and have them reflected in your code, and vice versa. You can think of the schema designer as a sort of visual code editor.
XSpecs can also visualize any code you write using the DDK using the palette above. This is a great way to get your whole team – business and technical alike – on the same page, and to make sure your code is always in sync with your business requirements.
Oh btw, XSpecs itself is built using the DDK! 🐶 🥣️
You can sign up for the beta at the XSpecs website.
- Event Sourcing and CQRS: DDK encapsulates the complexity of implementing an Event-Sourcing architecture and Command Query Responsibility Segregation (CQRS) in your applications.
- Decorator-based Command and Event Handlers: Easily register and handle commands and events using a declarative and intuitive decorator-based approach.
- Read Model Management: DDK manages Read Models and their handlers, ensuring efficient handling of domain-specific views of your data.
- Serialization: DDK comes with a built-in Serializer class that allows developers to serialize and deserialize domain events into a form that can be stored and retrieved.
- Command: An object that represents a single instruction to the system.
- Event: Represents something that has occurred in the system.
- AggregateRoot: An entity that is used to enforce business rules before new Events are emitted.
- Repository: Used to retrieve Aggregates from an EventStore and save newly applied events.
- EventStore: An interface representing a mechanism to store and retrieve events.
- ReadModel: Represents a read-only projection of your data.
- Registry: A singleton class that manages the registration and retrieval of command handlers, event handlers, and read model handlers.
More detailed documentation about specific modules, usage examples, and advanced features can be found in the documentation (coming soon).
For building apps using the DDK please refer to our documentation
- Clone the repository.
- Install dependencies with
yarn install. - Run
yarn testto ensure everything is set up correctly. - Dive into the source code, starting with examples provided to get a feel for how to utilize DDK in your application.
The DDK includes a comprehensive suite of tests to ensure its reliability and accuracy. To run these tests, use the command yarn test.
Contributions are always welcome! Feel free to open issues and pull requests. We aim to create a robust and reliable tool for everyone to use and improve.
We have a very high bar for automated testing set at a 100% coverage threshold. If you find we've somehow missed any tests, please open an issue, and we'll get it fixed as soon as possible.
Please make sure you are familiar with:
- Writing good commit messages
- Keeping the commit history clean and tidy
- Commitizen
- Semantic Release
📖 "Code is read much more often than it is written, so plan accordingly." - Anonymous