spring-modular-monolith

An e-commerce application following Modular Monolith architecture using Spring Modulith. The goal of this application is to demonstrate various features of Spring Modulith with a practical application.

This application follows modular monolith architecture with the following modules:

• Common: This module contains the code that is shared by all modules.
• Catalog: This module manages the catalog of products and store data in catalog schema.
• Orders: This module implements the order management and store the data in orders schema.
• Inventory: This module implements the inventory management and store the data in inventory schema.
• Notifications: This module handles the events published by other modules and sends notifications to the interested parties.

Goals:

• Implement each module as independently as possible.
• Prefer event-driven communication instead of direct module dependency wherever applicable.
• Store data managed by each module in an isolated manner by using different schema or database.
• Each module should be testable by loading only module-specific components.

Module communication:

• Common module is an OPEN module that can be used by other modules.
• Orders module invokes the Catalog module public API to validate the order details
• When an Order is successfully created, Orders module publishes "OrderCreatedEvent"
• The "OrderCreatedEvent" will also be published to external broker like RabbitMQ. Other applications may consume and process those events.
• Inventory module consumes "OrderCreatedEvent" and updates the stock level for the products.
• Notifications module consumes "OrderCreatedEvent" and sends an order confirmation email to the customer.

Prerequisites

• JDK 21
• Docker and Docker Compose
• Your favourite IDE (Recommended: IntelliJ IDEA)

Install JDK, Maven, Gradle using SDKMAN

$ curl -s "https://get.sdkman.io" | bash
$ source "$HOME/.sdkman/bin/sdkman-init.sh"
$ sdk install java 21.0.1-tem
$ sdk install gradle
$ sdk install maven

Task is a task runner that we can use to run any arbitrary commands in easier way.

$ brew install go-task
(or)
$ go install github.com/go-task/task/v3/cmd/task@latest

Verify the prerequisites

$ java -version
$ docker info
$ docker compose version
$ task --version

Using task to perform various tasks:

The default Taskfile.yml is configured to use Maven. Another Taskfile.gradle.yml is also created with Gradle configuration.

If you want to use Gradle instead of Maven, then add -t Taskfile.gradle.yml for the task commands.

For example:

$ task test` // uses Maven
$ task -t Taskfile.gradle.yml test` //uses Gradle

# Run tests
$ task test

# Automatically format code using spotless-maven-plugin
$ task format

# Build docker image
$ task build_image

# Run OpenRewrite Recipes
$ task open_rewrite

# Run application in docker container
$ task start
$ task stop
$ task restart

• Application URL: http://localhost:8080
• Actuator URL: http://localhost:8080/actuator
• Actuator URL for modulith: http://localhost:8080/actuator/modulith
• RabbitMQ Admin URL: http://localhost:15672 (Credentials: guest/guest)
• Zipkin URL: http://localhost:9411

Deploying on k8s cluster

• Install kubectl
• Install kind

$ brew install kubectl
$ brew install kind

Create a KinD cluster and deploy an app.

# Create KinD cluster
$ task kind_create

# deploy app to kind cluster 
$ task k8s_deploy

# undeploy app
$ task k8s_undeploy

# Destroy KinD cluster
$ task kind_destroy

• Application URL: http://localhost:30090
• RabbitMQ Admin URL: http://localhost:30091 (Credentials: guest/guest)
• Zipkin URL: http://localhost:30092