How to get JAVA_HOME and CATALINA_HOME environment variables in Java?

Question

I need to get the values of JAVA_HOME and CATALINA_HOME environment variable in Java. I am running a JAR (not WAR) and in System.getProperties() I could find only "java.home".

I read some other questions about it here, tried them, but could not make them work - I got different exceptions or just null value as a result.

I remember doing something similar many years ago using JNA, but it was in the 16-bit era of Windows. The latest JNA jar I could find is from 2011, running it in intelliJ works, but when I make a build in maven I get errors about not finding some classes.

I will continue investigating the JNA direction and will be glad to receive any assistance and/or ideas. I think that I'm only missing the right Maven dependency.

This is source code for my class so far:

//  C:\devtools\java-external-jars\jna-4.2.2\jna-platform-4.2.2.jar

import com.sun.jna.platform.win32.Advapi32Util;
import com.sun.jna.platform.win32.WinReg;

import java.io.IOException;
import java.io.InputStream;
import java.io.StringWriter;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.util.HashMap;
import java.util.Map;
import java.util.ArrayList;
import java.util.List;
import java.util.prefs.Preferences;

public class WinRegistryHelper {

    public static final String SYSTEM_ENVIRONMENT_KEY_PATH = "SYSTEM\\ControlSet001\\Control\\Session Manager\\Environment";

    public static final int HKEY_CURRENT_USER = 0x80000001;
    public static final int HKEY_LOCAL_MACHINE = 0x80000002;
    public static final int REG_SUCCESS = 0;
    public static final int REG_NOTFOUND = 2;
    public static final int REG_ACCESSDENIED = 5;

    private static final int KEY_ALL_ACCESS = 0xf003f;
    private static final int KEY_READ = 0x20019;
    private static final Preferences userRoot = Preferences.userRoot();
    private static final Preferences systemRoot = Preferences.systemRoot();
    private static final Class<? extends Preferences> userClass = userRoot.getClass();
    private static final Method regOpenKey;
    private static final Method regCloseKey;
    private static final Method regQueryValueEx;
    private static final Method regEnumValue;
    private static final Method regQueryInfoKey;
    private static final Method regEnumKeyEx;
    private static final Method regCreateKeyEx;
    private static final Method regSetValueEx;
    private static final Method regDeleteKey;
    private static final Method regDeleteValue;

    private WinRegistryHelper() {  }


    /**
     *
     * {@code String stringValue = Advapi32Util.registryGetStringValue(WinReg.HKEY_LOCAL_MACHINE, "SOFTWARE\\Microsoft\\Windows NT\\CurrentVersion", "ProductName");}
     */
    public static String registryGetStringValue(WinReg.HKEY root, String keyPath, String keyName) {
        // Read a string
        String stringValue = Advapi32Util.registryGetStringValue(root, keyPath, keyName);
        System.out.printf(keyName + " value is: %s\n", stringValue);
        return stringValue;
    }

    /**
     *
     * {@code int timeout = Advapi32Util.registryGetIntValue(WinReg.HKEY_LOCAL_MACHINE, "SOFTWARE\\Microsoft\\Windows NT\\CurrentVersion\\Windows", "ShutdownWarningDialogTimeout");}
     */
    public static int registryGetIntValue(WinReg.HKEY root, String keyPath, String keyName) {
        // Read an int (& 0xFFFFFFFFL for large unsigned int)
        int intValue = Advapi32Util.registryGetIntValue(root, keyPath, keyName);
        System.out.printf(keyName + " value is: %d (%d as unsigned long)\n", intValue, intValue & 0xFFFFFFFFL);
        return intValue;
    }

    /**
     *
     * {@code int timeout = Advapi32Util.registryGetLongValue(WinReg.HKEY_LOCAL_MACHINE, "SOFTWARE\\Microsoft\\Windows NT\\CurrentVersion\\Windows", "ShutdownWarningDialogTimeout");}
     */
    public static long registryGetLongValue(WinReg.HKEY root, String keyPath, String keyName) {
        // Read an int (& 0xFFFFFFFFL for large unsigned int)
        long longValue = Advapi32Util.registryGetLongValue(root, keyPath, keyName);
        System.out.printf(keyName + " value is: %d (%d as unsigned long)\n", longValue, longValue & 0xFFFFFFFFL);
        return longValue;
    }

    /**
     *
     * {@code Advapi32Util.registryCreateKeyPath(WinReg.HKEY_CURRENT_USER, "SOFTWARE\\StackOverflow");}
     */
    public static void registryCreateKeyPath(WinReg.HKEY root, String keyPath) {
        // Create a key and write a string
        Advapi32Util.registryCreateKey(root, keyPath);
    }

    /**
     * {@code Advapi32Util.registrySetStringValue(WinReg.HKEY_CURRENT_USER, "SOFTWARE\\StackOverflow", "url", "http://stackoverflow.com/a/6287763/277307");}
     */
    public static void registrySetStringValue(WinReg.HKEY root, String keyPath, String keyName, String keyValue) {
        Advapi32Util.registrySetStringValue(root, keyPath, keyName, keyValue);
    }

    public static void registrySetIntValue(WinReg.HKEY root, String keyPath, String keyName, int keyValue) {
        Advapi32Util.registrySetIntValue(root, keyPath, keyName, keyValue);
    }

    public static void registrySetLongValue(WinReg.HKEY root, String keyPath, String keyName, long keyValue) {
        Advapi32Util.registrySetLongValue(root, keyPath, keyName, keyValue);
    }

    /**
     *
     * {@code Advapi32Util.registryDeleteKey(WinReg.HKEY_CURRENT_USER, "SOFTWARE\\StackOverflow");}
     */
    public static void registryDeleteKey(WinReg.HKEY root, String keyPath) {
        // Delete a key
        Advapi32Util.registryDeleteKey(root, keyPath);
    }
}

Answer 1

There is a System.getenv method that helps to optain the value of the specified environment variable:

System.getenv("JAVA_HOME");
System.getenv("CATALINA_HOME");

if a security manager allows access to the environment variable. Otherwise, a SecurityException will be thrown.