Event Sourcing - Java

This repository contains a starter pack for Event Sourcing in Java It is a production grade starting point for your own event sourced application. The starter pack has everything you need to get started with event sourcing, including an event store, a projection store, and an event bus.

This starter pack implements a simple example for a Cooking Club Membership. But you're meant to replace this example with your own application.

Getting Started

To run this application you need to install Docker or Podman as a containerization tool. Once you have Docker or Podman installed, please open your Terminal (linux or mac) or Powershell (windows), clone this repository, and navigate to the scripts folder for your operating system and containerization tool.

git clone [email protected]:ambarltd/event-sourcing-typescript.git

cd event-sourcing-typescript/local-development/docker-scripts/linux # linux + docker
cd event-sourcing-typescript/local-development/docker-scripts/mac # mac + docker
cd event-sourcing-typescript\local-development\docker-scripts\windows  # windows + docker

cd event-sourcing-typescript/local-development/podman-scripts/linux # linux + podman
cd event-sourcing-typescript/local-development/podman-scripts/mac # mac + podman
cd event-sourcing-typescript\local-development\podman-scripts\windows  # windows + podman

# If you're using docker, make sure docker is up and running.
# If you're using podman, make sure podman is up and running. Also make sure there's an active podman machine.

# If you are using podman on windows, modify your podman machine to support linux directory permissions metadata translation.
wsl -u root -d podman-machine-default # or whatever your podman machine is called
echo [automount] >> wsl.conf
echo 'options = "metadata"' >> wsl.conf

Then start the application and run the demo.

# linux or mac
./dev_start.sh 
./dev_demo.sh

# windows
.\dev_start.ps1
.\dev_demo.ps1

You can then open your browser to:

• http://localhost:8080 to ping the backend
• http://localhost:8081 to view your event store
• http://localhost:8082 to view your projection store

How to Develop Your Own Application

Assuming you know event sourcing theory, developing on this application will feel very natural. Otherwise, don't worry - Ambar offers a free 1 day Event Sourcing course here.

To get a quick understanding of how this application works, please read the domain code in src/main/java/eventsourcing/domain/, the abstractions provided in src/main/java/eventsourcing/common/, and the README files also in src/main/java/eventsourcing/common/. With that reading done, here's a full picture:

1. src/main/java/eventsourcing/domain/: where you define aggregates, events, commands, queries, projections, and reactions. You will spend most of your time here.
2. src/main/java/eventsourcing/common/: a set of event sourcing abstractions. You will rarely need to edit files here, except for having to update the Serializer and Deserializer classes in src/main/java/eventsourcing/domain/common/serializedevent/ whenever you add or remove events.
3. Dependency injection and routes are defined with annotations, relying on Spring.

When developing your application for the fist time, we recommend you keep the Cooking Club Membership code as an example you can quickly navigate to. Once you have implemented several commands, queries, projections, and reactions, delete the Cooking Club Membership code. This will require you to delete its code in Domain, and serialization logic in Common/serializedEvent.

Additional Scripts

Whenever you build a new feature, you might want to restart the application, or even delete the event store and projection store. We have provided scripts to help you with that.

# linux or mac
./dev_start.sh # starts / restarts the application.
./dev_start_with_data_deletion.sh # use this if you want to delete your existing event store, and projection db, and restart fresh.
./dev_shutdown.sh # stops the application

# windows
.\dev_start.ps1 # starts / restarts the application.
.\dev_start_with_data_deletion.ps1 # use this if you want to delete your existing event store, and projection db, and restart fresh.
.\dev_shutdown.ps1 # stops the application

Deployment

To deploy this application to a production environment, you will simply need to build the code into a docker image, and deploy it to your cloud provider. We have provided infrastructure starter packs for various clouds in this repository.

Support

If you get stuck, please feel free to ask questions in the #event-sourcing channel of our Slack community. Or if you need further help like a free private walkthrough, simply book one here.