I found a solution to set environment variables on IntelliJ that has been working very well for me, and is incredibly simple. Let me show you.

This is the program (you can copy and paste it) we're using to test:

package com.javasd.intelijenv;

import java.util.Map;

public class Main {
    public static void main(String[] args) {
        Map<String, String> env = System.getenv();
        for (String envName : env.keySet()) {
            System.out.format("%s=%s%n", envName, env.get(envName));
        }

        System.out.println("My home directory: " + System.getenv("MY_VAR"));
    }
}

This program basically loads all environment variables, show them on the console, and try to show an env variable. Also, it assumes that you had created the MY_VAR env variable before calling IntelliJ IDEA, by doing something like:

$ export MY_VAR="This is my adorable var :)"
$ idea

Please, notice that we're calling IntelliJ IDEA in the same terminal (or session, or window) where we created the environment variable. If you create the variable and call the IDEA from the icon, the solution won't work because the IDEA will create its own session.

So, if run it without the correct configuration you will get something line this in your console:

Please, notice that you have just a few variables, and that MY_VAR is null.

Here's configuration I use to load the environment variables:

1. Click on the "Select Run/Debug Configurations" in your project and select "Edit Configurations":

2. Then, click on the the button with "..." on the right side of the "Environment Variables" section:

3. You'll see a pop-up. Check the checkbox on the bottom-left which has the label "Include parent environment variables":

That's it!!!

If you run your program now you will see something like this on your console:

You can see all the environment variables and, of course, your "MY_VAR" variable, with the right value!

Beyond the Basics

Usually, for security reasons, we don't want to keep all the environment variables visible. What we want to do is to make those variables visible only while the IntelliJ (or our program) is running.

So, no sensitive variables should be visible on the environment neither before you call Intellij nor after you close it.

Also, you want to keep those variables in a file (typically with a .env extension) to make it easy to manipulate and for security reasons.

To achieve this, there are some useful programs (you can Google them), but my favorite one is the env-cmd.

Let's say you have a test.env file with the following content:

MY_TEST_VAR=I live in the test.env file.

If you call IntelliJ by doing this:

$ env-cmd test.env idea

And edit your program to show "MY_TEST_VAR", and run it, you will see this on the IntelliJ's console:

But if you quit the IntelliJ, and look for your variable, you will see that the var doesn't exist (you can use env to confirm):

At this point, I hope you're able to play with your own solutions: create shell scripts with variables set inside, test other programs (direnv, autoenv, etc.), and so on.

I could not get environment variables to work when IntelliJ Build and run property was using Gradle. I am not sure what the root cause is, but switching to IntelliJ IDEA solved the problem. Go to Preferences -> Build, Execution, Deployment -> Build Tools -> Gradle. Then change Build and run using: to IntelliJ IDEA.