Setting environment variable in Java 8

Question

I have similar code to this one (update environment variable):

private static void setEnv(Map<String, String> envs) {
    try {
        Class<?> pec = Class.forName("java.lang.ProcessEnvironment");
        Field tef = pec.getDeclaredField("theEnvironment");
        tef.setAccessible(true);

        Map<String, String> env = (Map<String, String>) tef.get(null);
        env.clear();
        env.putAll(envs);

        Field tcief = pec.getDeclaredField("theCaseInsensitiveEnvironment");
        tcief.setAccessible(true);
        Map<String, String> cienv = (Map<String, String>) tcief.get(null);
        cienv.clear();
        cienv.putAll(envs);
    } catch (Exception e) {
        logger.printStackTrace(e);
    }
}

I've written some unit tests for this code and now I'm testing on Java 8 (1.8.0). This code doesn't work for Run in JUnit, but works when is running as Debug (with and without breakpoints). Doesn't work means I get my environment variable (PATH) like this

String path = System.getenv("PATH");

and I see there is no my path (c:\\temp). Testing on Java 7 (1.7.0_51) works fine, all Javas are 32-bit, I'm using no additional threads. Do you have any ideas how to solve this?

Answer 1

The problem was in the case sensitivity keys. Parameter envs was created as

Map<String, String> envs = new HashMap<String, String>();

but creating it as

Map<String, String> envs = new TreeMap<String, String>(String.CASE_INSENSITIVE_ORDER);

solved the problem. I got different results for env["Path"], env["PATH"] and so on.

Answer 2

You can also achieve this using System Stubs - https://github.com/webcompere/system-stubs

Map<String, String> someMap = ...; // work out the env variables
EnvironmentVariables environmentVariables = new EnvironmentVariables(someMap);

The environment variables are applied to the environment while the object is active. This is achieved either through its JUnit 4 or 5 plugins, or via using the execute method on the object to wrap around the executable code.