Setting global variables at runtime for TestNG Suite?

I have written a TestNG Suite in Java that will be ran on another system using a test account. The credentials for this account are stored in a password vault and are obtained through an API. Each of the tests requires this login information, and every test class will call the password vault API. I have this as a step in the setup method of each test class.

I would like to reduce it to just a single API call if possible. Would it be possible to obtain the credentials at the beginning of the suite and pass those to each of the test classes?

I looked at this as a potential solution: How to add parameter at runtime in specific test

I would prefer to not modify the XML in this way, as I found this will expose the login information in TestNG's results report.

Solution

Here's how you go about doing it.

Build a TestNG listener by implementing the TestNG interface org.testng.ISuiteListener
Within its onStart() method, include the logic to retrieve the credentials from the vault and then set them as attributes on the ISuite object (which you get as a parameter to the onStart() method)

    suite.setAttribute("username", 'foo');
    suite.setAttribute("password", "foopassword");

Now within your test method, you can retrieve the credentials as seen below

org.testng.ITestResult itr = org.testng.Reporter.getCurrentTestResult();
org.testng.ISuite currentSuite = itr.getTestContext().getSuite();
String username = Optional.ofNullable(currentSuite.getAttribute("username"))
        .map(Object::toString)
        .orElseThrow(() -> new IllegalArgumentException("Could not find a valid user name"));
String password = Optional.ofNullable(currentSuite.getAttribute("password"))
        .map(Object::toString)
        .orElseThrow(() -> new IllegalArgumentException("Could not find a valid password"));

You can now include a reference to this suite using the <listeners> tag in your suite xml file [ for details refer here ] (or)
You can make this listener a mandatory listener which would always get invoked automatically without needing it to be explicitly referenced, by wiring it in as a service loader loaded listener [ for details refer here ]