A Java port of the Ruby dotenv project (which loads environment variables from a .env
file). java-dotenv also offers a Kotlin DSL.
From the original Ruby project:
Storing configuration in the environment is one of the tenets of a twelve-factor app. Anything that is likely to change between deployment environments–such as resource handles for databases or credentials for external services–should be extracted from the code into environment variables.
But it is not always practical to set environment variables on development machines or continuous integration servers where multiple projects are run. Dotenv load variables from a .env file into ENV when the environment is bootstrapped.
Environment variables listed in the host environment override those in .env
.
Use dotenv.get("...")
instead of Java's System.getenv(...)
.
<dependency>
<groupId>io.github.cdimascio</groupId>
<artifactId>java-dotenv</artifactId>
<version>4.1.0</version>
</dependency>
compile 'io.github.cdimascio:java-dotenv:4.1.0'
Use dotenv.get("...") instead of Java's System.getenv(...). Here's why.
Create a .env
file in the root of your project
# formatted as key=value
MY_ENV_VAR1=some_value
MY_EVV_VAR2=some_value
With Java
import io.github.cdimascio.dotenv.Dotenv;
Dotenv dotenv = Dotenv.load();
dotenv.get("MY_ENV_VAR1")
or with Kotlin
import io.github.cdimascio.dotenv.dotenv
val dotenv = dotenv()
dotenv["MY_ENV_VAR1"]
-
Create an assets folder
-
Add
env
(no dot) to the assets folder. -
Configure dotenv to search
/assets
for a file with nameenv
val dotenv = dotenv { directory = "/assets" filename = "env" // instead of '.env', use 'env' } dotenv["MY_ENV_VAR1"]
Note: The above configuration is required because dot files in /assets
do not appear to resolve on Android. (Seeking recommendations from the Android community on how java-dotenv
configuration should work in order to provide the best experience for Android developers)
Alternatively, if you are using Provider android.resource
you may specify
directory = "android.resource://com.example.dimascio.myapp/raw"
Configure java-dotenv
once in your application.
With Java
Dotenv dotenv = Dotenv.configure()
.directory("./some/path")
.ignoreIfMalformed()
.ignoreIfMissing()
.load();
or with Kotlin
val dotenv = dotenv {
directory = "./some/path"
ignoreIfMalformed = true
ignoreIfMissing = true
}
Note, environment variables specified in the host environment take precedence over those in .env
.
With Java
dotenv.get("HOME");
dotenv.get("MY_ENV_VAR1", "default value");
or with Kotlin
dotenv["HOME"]
dotenv["MY_ENV_VAR1"] ?: "default value"
Note, environment variables specified in the host environment take precedence over those in .env
.
With Java
for (DotenvEntry e : dotenv.entries()) {
System.out.println(e.getKey());
System.out.println(e.getValue());
}
or with Kotlin
for (e in dotenv.entries()) {
println(e.key)
println(e.value)
}
-
path
specifies the directory containing.env
. Dotenv first searches for.env
using the given path on the filesystem. If not found, it searches the given path on the classpath. Ifdirectory
is not specified it defaults to searching the current working directory on the filesystem. If not found, it searches the current directory on the classpath.Java example
Dotenv .configure() .directory("/some/path") .load()
Kotlin Dsl example
dotenv { directory = "/some/path" }
-
Use a filename other than
.env
. Recommended for use with Android (see details)Java example
Dotenv .configure() .filename("myenv") .load()
Kotlin Dsl example
dotenv { filename = "myenv" }
-
Do not throw when
.env
entries are malformed. Malformed entries are skipped.Java example
Dotenv .configure() .ignoreIfMalformed() .load()
Kotlin Dsl example
dotenv { ignoreIfMalformed = true }
-
Do not throw when
.env
does not exist. Dotenv will continue to retrieve environment variables that are set in the environment e.g.dotenv["HOME"]
Java example
Dotenv .configure() .ignoreIfMissing() .load()
Kotlin Dsl example
dotenv { ignoreIfMissing = true }
- with Maven (simple)
- with Spring MVC
- with Spring Webflux
- with Android
- see Kotlin DSL tests
- see Java tests
Q: Should I deploy a .env
to e.g. production?
A: Tenant III of the 12 factor app methodology states "The twelve-factor app stores config in environment variables". Thus, it is not recommended to provide the .env file to such environments. dotenv, however, is super useful in e.g a local development environment as it enables a developer to manage the environment via a file which is more convenient.
Using dotenv in production would be cheating. This type of usage, however is an anti-pattern.
Q: Why should I use dotenv.get("MY_ENV_VAR")
instead of System.getenv("MY_ENV_VAR")
A: Since Java does not provide a way to set environment variables on a currently running process, vars listed in .env
cannot be set and thus cannot be retrieved using System.getenv(...)
.
Q: Should I have multiple .env files?
A: No. We strongly recommend against having a "main" .env file and an "environment" .env file like .env.test. Your config should vary between deploys, and you should not be sharing values between environments.
In a twelve-factor app, env vars are granular controls, each fully orthogonal to other env vars. They are never grouped together as “environments”, but instead are independently managed for each deploy. This is a model that scales up smoothly as the app naturally expands into more deploys over its lifetime.
– The Twelve-Factor App
Q: Should I commit my .env
file?
A: No. We strongly recommend against committing your .env
file to version control. It should only include environment-specific values such as database passwords or API keys. Your production database should have a different password than your development database.
Q: What happens to environment variables that were already set?
A: java-dotenv will never modify any environment variables that have already been set. In particular, if there is a variable in your .env
file which collides with one that already exists in your environment, then that variable will be skipped. This behavior allows you to override all .env
configurations with a machine-specific environment, although it is not recommended.
Q: What about variable expansion in .env
?
A: We haven't been presented with a compelling use case for expanding variables and believe it leads to env vars that are not "fully orthogonal" as The Twelve-Factor App outlines. Please open an issue if you have a compelling use case.
Note and reference: The FAQs present on motdotla's dotenv node project page are so well done that I've included those that are relevant in the FAQs above.
Contributions are welcome!
see CONTRIBUTING.md
see LICENSE (Apache 2.0)