This repository provides practical examples and code snippets to help Java developers implement effective architectural concepts and design patterns with a main focus on performance, scalability, and resiliency as primary quality attributes.
These examples are designed to complement the curriculum of the đź“š Designing High-Performance, Scalable, and Resilient Applications Course.
If you're looking to enhance your skills and design secure, high-performing applications, 🎓 enroll now and master the principles of modern Java architecture!
For more resources and insights, feel free to visit my website.
Among the architectural styles, design tactics, and patterns demonstrated in this project:
- Layered architecture, Hexagonal architecture, Event-driven microservices architecture
- API-driven development approach
- Schema-first development approach
- Shared-nothing database approach
- Schema registry
- REST architectural style (e.g., RESTful APIs)
- Scalability (e.g., horizontal scalability)
- Location decoupling
- Resiliency
- Caching (e.g., local/embedded)
- Asynchronous logging
- Change data capture design pattern
- Listen to yourself design pattern
- Data transfer object enterprise application pattern
The purpose of this application is to have a platform where customers can find products, shop around using a cart, check out the products and initiate payments.
Below is a breakdown and description of each module in the current project.
| Module | Description |
|---|---|
Account service |
Manages user data and exposes a GraphQL interface for retrieving accounts. It includes a prefilled user account for demonstration purposes. |
Product service |
Manages the product catalog and exposes an API to create, retrieve, update, and delete products. It includes a prefilled product catalog for quick setup. |
Shopping cart service |
Manages the user's shopping cart, exposing an API to create, retrieve, update, delete, and check out items in the cart. |
Order service |
Manages user orders and provides an API to retrieve historical orders and update them as needed. |
Payment service |
Processes payments for orders using an external payment system. |
Shipping service |
Simulates the shipment of successful orders to their destination after payment processing is completed. |
Notification service |
Logs all received events to the console for monitoring and debugging purposes. |
Message schema library |
Contains AVRO message definitions used across services to ensure consistent data formats. |
End to end sequence diagram:
sequenceDiagram
actor User
User->>Product Service: Get Products
User->>Shopping Cart Service: Save Products In Cart
User->>Shopping Cart Service: Checkout Cart Items
Shopping Cart Service->>Order Service: Publish Order Created Event
Order Service->>Payment Service: Trigger Payment Command
critical Payment
Payment Service->>Payment Gateway: Trigger Payment
Payment Gateway-->>Payment Service: Payment Status (e.g., APPROVED/FAILED)
end
Payment Service-->>Order Service: Publish Payment Status Updated Event
Order Service->>Notifications Service: Publish Payment Status Updated Event
alt Payment APPROVED
Order Service->>Shipping Service: Trigger Shipping Command
Shipping Service-->>Order Service: Publish Shipping Status Updated Event (e.g., IN_PROGRESS)
critical Shipping
Shipping Service->>Shipping Gateway: Trigger Shipping
Shipping Gateway->>Shipping Service: Shipping Status (e.g., COMPLETED/FAILED)
end
Shipping Service-->>Order Service: Publish Shipping Status Updated Event (e.g., COMPLETED/FAILED)
Order Service->>Notifications Service: Publish Shipping Status Updated Event
end
Events state diagram:
stateDiagram-v2
[*] --> NEW
NEW --> PAYMENT_APPROVED
NEW --> PAYMENT_FAILED
PAYMENT_FAILED --> [*]
PAYMENT_APPROVED --> SHIPPING_IN_PROGRESS
SHIPPING_IN_PROGRESS --> SHIPPING_COMPLETED
SHIPPING_IN_PROGRESS --> SHIPPING_FAILED
SHIPPING_FAILED --> [*]
SHIPPING_COMPLETED --> [*]
Among the technologies, frameworks, and libraries included in this project:
- Spring Boot
- JdbcTemplate (e.g., query, update, batch update)
- Caffeine caching
- Kafka
- PostgreSQL
- Flywaydb
- Debezium
- Testcontainers
- Resilience4j (e.g., circuit breaker, bulkhead)
- Traefik (i.e., HTTP reverse proxy and load balancer)
- AVRO and JSON data format
- OpenAPI specification
- GraphQL
- Logback
- Spotless code formatter
- Docker compose
- ArchUnit
Please make sure you have properly installed (and configured):
- JDK 21 (i.e., latest LTS)
- Docker
- cURL
- Postman
./mvnw clean package
Note: Please start the Docker agent up front, otherwise, the tests fail.
./bootstrap.sh
To check if all Docker containers are up and running execute the below command:
docker ps -a
Important: On Windows using Docker compose v2 there is a known limitation while horizontally scaling a service by using port ranges like "8080-8081:80".
At the moment, the workaround is to simply copy-paste (multiple times) the same service inside the Docker compose YAML file and explicitly assign different ports to each.
The PostgreSQL connector is used to monitor and record the row-level changes in the PostgreSQL database schema.
Note: please make sure all services (e.g., PostgreSQL and Kafka) are up and running before registering the connector
./debezium-register-postgres.sh
Once the PostgreSQL connector is successfully registered, it reads the database log and produces events for row-level INSERT, UPDATE, and DELETE operations, emitting such events to the Kafka topic (in this case to the ecommerce-product-cdc-topic).
Open a browser and navigate to http://localhost:26060 to access the Traefik UI (it shows endpoints, routes, services, etc.).
Open a browser and navigate to http://localhost:19000 to access the Kafdrop UI (it shows topics, partitions, consumers, messages, etc.).
Open a browser and navigate to http://localhost:18080 to access the Debezium UI (it shows the PostgreSQL connector).
Open a browser and navigate to http://localhost:55080/graphiql?path=/graphql to access the GraphiQL in-browser tool for writing, validating, and testing GraphQL account-service queries.
- open Postman
- import the provided API collections, corresponding to each project, as follows:
./ecommerce-app/order-service/postman./ecommerce-app/product-service/postman./ecommerce-app/shopping-cart-service/postman
- to simulate a basic test scenario please trigger the below requests (in this sequence):
GET http://localhost:{{port}}/products
POST http://localhost:{{port}}/cart/{{userId}}/items
POST http://localhost:{{port}}/cart/{{userId}}/checkout
GET http://localhost:{{port}}/orders/{{userId}}/history
Note: the ports (i.e., service port or Traefik load balancer port) are already configured as variables in the Postman collections
A few, optional, TODOs for further enhancements might be:
- implement a scheduler to reply unprocessed/failed events
- implement API pagination
- implement database bulk updates for the remaining APIs
This project is licensed under the MIT License.
Please see the LICENSE file for full license.
/**
* eCommerce Application
*
* Copyright (c) 2022 - 2024 Ionut Balosin
* Website: www.ionutbalosin.com
* X: @ionutbalosin | LinkedIn: ionutbalosin | Mastodon: ionutbalosin@mastodon.social
*
*
* MIT License
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in all
* copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
* SOFTWARE.
*
*/