Subscription-Tool

A rather simple Spring Boot application to manage subscriptions (e.g. to a newsletter).

Usage

On /subscribe a new subscription can be added. Before a subscription becomes active, the double opt-in process has to be completed by clicking on the link in the confirmation email.

On /unsubscribe an existing subscription can be removed.

On /manage all subscriptions can be managed. It is possible to activate subscriptions (skipping the double opt-in process) and delete subscriptions. A list of all active subscriptions can be copied to the clipboard to be used in an email.

Setup

Requirements

To run the application, Java 25 or higher, a PostgreSQL database and an SMTP server are required.

Database

A PostgreSQL database is required to run the application. To set up a local database, you can use Docker:

docker run --name dev-subscriptiontool -e POSTGRES_PASSWORD=PASSWORD -p 5000:5432 -d postgres
docker exec -it dev-subscriptiontool psql -U postgres
CREATE DATABASE subscriptiontool;

Configuration

Change the configuration values in application.properties to match your environment.

Basic authentication protects private endpoints (e.g., /actuator). The username and password can be configured by using the following properties:

• subscriptiontool.web.username=USERNAME
• subscriptiontool.web.password=PASSWORD

The password is hashed using Bcrypt. To create a password hash, use the following command: mkpasswd -m bcrypt (on Debian GNU/Linux mkpasswd is part of the whois package).

Translation

Translation to other languages can be done by editing the messages.properties file.

systemd service

To run the application as a systemd service, create a dedicated user (e.g. spring) first. Then place the executable JAR file in /opt/spring and create a service unit:

[Unit]
Description=subscription-tool
After=syslog.target

[Service]
User=spring
ExecStart=java -Dserver.port=8090 -jar /opt/spring/subscription-tool.jar
SuccessExitStatus=143 

[Install] 
WantedBy=multi-user.target

(/etc/systemd/system/subscription-tool.service)

Use systemctl enable subscription-tool.service to enable the service. When running, the application will be available at http://localhost:8090/.

Security

When the application is exposed to the internet, it should be used behind a reverse proxy. For example, use nginx to handle secure TLS connections to the application. Also, set up a reasonable rate limit to avoid DOS and brute force attacks.