Этот код работает для меня в Linux и Mac:
public static void main(String[] args) throws IOException {
FirefoxOptions options = new FirefoxOptions();
FirefoxDriver driver = new FirefoxDriver(options);
String userPrefsFileContent = readFile(driver.getCapabilities().getCapability("moz:profile") + "/prefs.js");
String extensionUuid = getExtensionUuid(userPrefsFileContent);
driver.quit();
}
private static String getExtensionUuid(String userPrefsFileContent) {
String uuid = null;
String[] usersPrefsList = userPrefsFileContent.split(";");
for (String currentPref : usersPrefsList) {
if (currentPref.contains("extensions.webextensions.uuids")) {
uuid = currentPref.split(":")[1].replaceAll("\"", "").replace("}", "")
.replace(")", "").replace("\\", "");
}
}
if(uuid.contains(",")) {
uuid = uuid.split(",")[0];
}
return uuid;
}
private static String readFile(String pathname) throws IOException {
File file = new File(pathname);
StringBuilder fileContents = new StringBuilder((int) file.length());
String lineSeparator = System.getProperty("line.separator");
try (Scanner scanner = new Scanner(file)) {
while (scanner.hasNextLine()) {
fileContents.append(scanner.nextLine()).append(lineSeparator);
}
}
return fileContents.toString();
}