DotEnvLoader

Java does not have build-in simple way to load .env files like load_dotenv in python.

DotEnvLoader is a lightweight library for loading environment variables from .env files into your Java application with simple API.

Installation:

Add the following dependency to your pom.xml:

<dependency>
    <groupId>io.github.rohergun</groupId>
    <artifactId>dotenv-loader</artifactId>
    <version>1.0.0</version>
</dependency>

Usage

Create a .env file in your project root:

DATABASE_URL=jdbc:postgresql://localhost:5432/mydb
API_KEY=supersecretkey
SERVER_PORT=8080

Load it at application startup:

// Load from project root (default)
DotEnvLoader.load();

// Option for loading from custom path
DotEnvLoader.load("/path/to/custom.env");

// Access values
String dbUrl = EnvContext.get("DATABASE_URL");
String port = EnvContext.get("SERVER_PORT", "8080"); // with default fallback

EnvContext.get() checks the .env store first, then falls back to the real OS environment,
then returns null (or the supplied default).

.env Syntax

# Each line is KEY=value
FAV_SNACK=donuts
USERNAME=coolusername
EMPTY_VAL=

# Keys must be SCREAMING_SNAKE_CASE
DATABASE_URL=jdbc:postgresql://localhost:5432/mydb

• Keys must be SCREAMING_SNAKE_CASE — uppercase letters, digits, and underscores only
• Values can be any characters, including = signs
• Empty values are allowed (KEY=)
• Blank lines are ignored
• If the file is missing it is silently skipped — no error is thrown

Error Handling

A DotEnvParseException is thrown if any non-empty line is malformed.
The exception includes the file name, line number, and the offending line to make debugging straightforward:

Parse error in '.env' at line 3: missing '=' separator — expected KEY=value format
offending line: "badline"

Building from Source:

git clone https://github.com/rohergun/DotEnvLoader.git
cd dotenv-loader
mvn verify