E-commerce application

This is a Spring Boot backend microservices application that I built to practice and demonstrate my ability to implement modern best practices and technologies.

Architecture Overview

The project includes a standard e-commerce workflow:

• Admin can create new courses and authors.
• A user can create an order, which reserves a spot in a course.
• A user can pay for the order, and if the payment is successful, the system sends an email.

Below is a detailed description of each service.

API

Provides shared definitions and classes for communication between microservices.
It contains:

• .proto files defining the gRPC contracts.
• Auto-generated gRPC classes.
• DTO classes for serialization and deserialization.

Catalog

Handles all operations related to authors and courses. It stores data in PostgreSQL and for GET operations caches data in Redis. These are the API endpoints:

• POST /api/rest/author/create – allows an admin to create an author.
• POST /api/rest/course/create – allows an admin to create a course.
• GET /api/rest/course/all – allows users to retrieve all available courses.

Order

Includes all operations to create and validate orders. After a user sends a request to create an order, the service sends a gRPC request to the Catalog service to validate the order information. If the validation is successful, the order is saved in the PostgreSQL database.

These are the API endpoints:

• POST /api/rest/order/create – allows a user to create an order.
• GET /api/rest/order/get/{id} – allows a user to retrieve an order by ID.

Payment

Handles the payment operation. A user sends a request to pay for an order, and the Payment service sends a gRPC request to the Order service to validate the payment information. If it is valid, a Kafka message is sent to the Message and Order services. The Message service sends an email about the successful payment, and the Order service updates the status of the order to PAID.

• POST /api/rest/payment – allows a user to pay for an order.

Message

Receives Kafka messages from the Payment service and sends an email via Gmail SMTP.

Gateway Server

The service exposes a port to communicate with all REST API endpoints from external clients.
It also provides JWT validation, a circuit breaker, and a retry mechanism for all microservices.

Technical stack

• Spring Framework – a powerful and widely used framework for building scalable Java web applications.
  This project leverages key Spring modules, including Spring Boot, Spring Web, Spring Data, and Spring Cloud.
• PostgreSQL – a database for storing orders and courses.
• Redis – a caching system for storing courses information.
• Kafka – a broker for asynchronous messaging between services.
• gRPC – a high-performance RPC framework that enables efficient synchronous communication between microservices.
• Docker – a platform for building and running containerized applications; this project uses the Buildpacks plugin to create images.
• Kubernetes – a container orchestration system that manages deployment, scaling, load balancing, and service discovery.
• Helm – a package manager for Kubernetes that simplifies the deployment and management of applications.
• OAuth2 – an open standard for secure authentication and authorization, used here with JWT validation.
• Keycloak – an identity and access management solution that provides user authentication, registration, and authorization.

Deployment

The e-commerce application is deployed on Kubernetes using Helm charts. The helm/ folder in the project contains all the necessary Helm-related files.
It’s necessary to install dependencies first: PostgreSQL, Redis, Kafka, and Keycloak. For this purpose, Bitnami Helm charts are used.

#PostgreSQL
helm install db bitnami/postgresql --set auth.database=appdb --set auth.username=appuser --set auth.password=supersecret

#Redis
helm install cache bitnami/redis --set architecture=standalone --set auth.password=redissecret

#Kafka
helm install my-kafka bitnami/kafka -f values.yaml

#Keycloak
helm install my-keycloak bitnami/keycloak -f values.yaml

After installing dependencies, you can deploy the microservices using their Helm charts:

helm install catalog ./catalog

Contact

If you have any questions, feedback or proposals, feel free to reach out:

• Email: ilyakonst95@gmail.com
• LinkedIn: Ilya Kanstanchuk
• Telegram: @tdespairedt