Environment Variables in Fortress

Our first look at environment variables will demonstrate how to set, get, and list these configuration parameters in Java.

import java.util.Map;

public class EnvironmentVariables {
    public static void main(String[] args) {
        // To set a key/value pair, use System.setProperty
        // To get a value for a key, use System.getenv
        // System.getenv will return null if the key isn't present in the environment
        System.setProperty("FOO", "1");
        System.out.println("FOO: " + System.getenv("FOO"));
        System.out.println("BAR: " + System.getenv("BAR"));

        // Use System.getenv() to get all environment variables
        // This returns a Map<String, String> of all key/value pairs
        System.out.println();
        Map<String, String> env = System.getenv();
        for (String key : env.keySet()) {
            System.out.println(key);
        }
    }
}

Running the program shows that we pick up the value for FOO that we set in the program, but that BAR is null.

$ java EnvironmentVariables
FOO: null
BAR: null

The list of keys in the environment will depend on your particular machine.

PATH
JAVA_HOME
USER
...

If we set BAR in the environment first, the running program picks that value up.

$ export BAR=2
$ java EnvironmentVariables
FOO: null
BAR: 2
...

Note that in Java, System.setProperty() sets a system property, not an environment variable. Environment variables are typically set outside of the Java program and cannot be modified at runtime. The System.getenv() method retrieves the environment variables.

Context in Fortress

Signals in Fortress

Learn X By Example

Title here

Environment Variables in Fortress