Is there a way to have a Java program set an environment variable in Windows and/or Linux system?
I'm creating a Java application for a desktop system, which I hope will be used in Windows, Linux and Mac. But I'm unsure if I can make the installer set an environment variable for the application.
The environment is only ever passed into a child process, never out of a child process. So if what you want is to be able to write something like this:
java ProgramThatSetsAnEnvironmentVariable
java ProgramThatUsesTheEnvironmentVariable
then no, that's not possible.
But if what you want is to for a Java program to run a program, and you want it to pass in additional environment variables, then yes, that's possible, by using java.lang.ProcessBuilder's environment() method.
This can be achieved via reflection.
Use the following code:
public static void setEnv(String key, String value) {
try {
Map<String, String> env = System.getenv();
Class<?> cl = env.getClass();
Field field = cl.getDeclaredField("m");
field.setAccessible(true);
Map<String, String> writableEnv = (Map<String, String>) field.get(env);
writableEnv.put(key, value);
} catch (Exception e) {
throw new IllegalStateException("Failed to set environment variable", e);
}
}
