Environment variables

What are they

Environment variables allow to to store a piece of configuration data outside of the main code of our application. This allows us to hide this configuration data if it is sensitive, or swap it out if the app needs to be configured differently in different environments.

Declaring environment variables

Make a file in the very root of the project called .env and add some variables to it in the following format:

DB_URL=jdbc:mysql://localhost:3306/mydb
DB_USER=root
DB_PASSWORD=supersecret

DANGER

Environment variables tend to contain sensitive information. For this reason, we should not check them into version control.

Create a file called .gitignore at the root of your project and add .env to it. You can add any other file or folder you want to exclude from Git to this file.

Reading environment variables

Add java-dotenv as a dependency in pom.xml.

<dependency>
    <groupId>io.github.cdimascio</groupId>
    <artifactId>java-dotenv</artifactId>
    <version>5.2.2</version> <!-- Check for the latest version -->
</dependency>

In any file you want to use the environment variables, import the Dotenv class

import io.github.cdimascio.dotenv.Dotenv;

then call Dotenv.load() to get the variables

// Will automatically look for a .env file in the root directory:
Dotenv dotenv = Dotenv.load();

String dbUrl = dotenv.get("DB_URL");
String dbUser = dotenv.get("DB_USER");
String dbPassword = dotenv.get("DB_PASSWORD");

System.out.println("Database URL: " + dbUrl);
System.out.println("Database User: " + dbUser);