demo-email-server

This project is a demo showing how a very rudimentary web server could be implemented by using Java and Spring Boot. The use case for this project should show a simple email server.

Running the project

Prerequisites

• Java 24
• Docker

Run the project within test environment

1. Adjust the src/test/resources/application.yml file and set the wanted spam-email.address to the one you'd like the email server to use for spam emails.
2. Run the test application info.deckermail.demoemailserver.TestDemoEmailServerApplication.main directly. It will spin up the application and the pre-configured Postgres DB in a test environment.

Run the project with Docker Compose

1. Clone the repository
2. Build the applications Docker image using Maven:

   ./mvnw spring-boot:build-image -Dspring-boot.build-image.imageName=deckermail/demo-email-server

3. Adjust the application-dc.yml file and set the wanted spam-email.address to the one you'd like the email server to use for spam emails.
4. Start the application together with the required Postgres DB using Docker Compose:

   docker compose up

5. The application should now be running at http://localhost:8080. You can check the health of the application by opening http://localhost:8080/actuator/health in your browser.
6. After exploring the application, you can stop it by running:

   docker compose down -v

API Documentation

The API documentation is available at http://localhost:8080/swagger-ui/index.html.

Shortcuts

Due to external time constraints, the project contains several shortcuts which should be avoided in production. To show that I'm aware of them and that I'm able to handle them differently, I list them here:

• Input validation: The input validation is very rudimentary. Usually, you'd try to validate emails which are inserted. Since there are so many different email formats, this is not a trivial task. From my point of view, only email addresses which already received an email, and you know that are valid email addresses. See https://stackoverflow.com/a/201378 for more information.
• Tests/TDD: The project contains a number of tests which should confidentially cover the most important functionality. However, they are not complete and are not written in a TDD manner. I know how to build a project in TDD style, but it takes me more time than adding some functional tests for the core logic.
• Huge data amounts: The project is made by the principle of "keep it simple and stupid". This also means that not every bit of code is optimized for large data amounts. E.g.: The email spam detection is done by querying over all emails. This could block other database queries and could be done by chunking the deletions and processing them with a small delay if necessary. However, this would also add complexity to the code and is not necessary for a demo project.