Access fields of a TestNG test class from a TestListenerAdapter - reflection

Question

Background
I have the following situation:
My test-classes implement org.testng.ITest
They all have a Helper containing info on the current test environment (e.g. device-under-test)
For example:
com.company.appundertest.Helper h;
public class TestClass implements org.testng.ITest {
private String testName;
//Helper is initialized externally in Factory + DataProvider
//and passed to Constructor.
public TestClass(com.company.appundertest.Helper hh) {
this.h = hh;
//constructor sets the test-name dynamically
//to distinguish multiple parallel test runs.
this.testName = "some dynamic test name";
}
#Override
public String getTestName() {
return this.testName;
}
#Test
public void failingTest() {
//test that fails...
}
}
These test-classes are executed in parallel using Factory and parallel data-provider.
Upon Test Failure, I need to access variables within the Helper instance of the failing test-class. These will be used to identify the environment at the point of failure (e.g. take screenshot on failing device).
This problem essentially boils down to:
How would I access fields within the TestNG test-class?
References
Access to private inherited fields via reflection in Java

Answer 1

Here's an example method. You can insert this in a Test Listener class (which extends TestListenerAdapter)
public class CustomTestNGListener extends TestListenerAdapter{
//accepts test class as parameter.
//use ITestResult#getInstance()
private void getCurrentTestHelper(Object testClass) {
Class<?> c = testClass.getClass();
try {
//get the field "h" declared in the test-class.
//getDeclaredField() works for protected members.
Field hField = c.getDeclaredField("h");
//get the name and class of the field h.
//(this is just for fun)
String name = hField.getName();
Object thisHelperInstance = hField.get(testClass);
System.out.print(name + ":" + thisHelperInstance.toString() + "\n");
//get fields inside this Helper as follows:
Field innerField = thisHelperInstance.getClass().getDeclaredField("someInnerField");
//get the value of the field corresponding to the above Helper instance.
System.out.println(innerField.get(thisHelperInstance).toString());
} catch (NoSuchFieldException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (SecurityException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (IllegalArgumentException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (IllegalAccessException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
Call this as follows:
#Override
public void onTestFailure(ITestResult tr) {
getCurrentTestHelper(tr.getInstance());
}

Answer 2

The #Vish 's solution is good, but you can avoid reflection with:
interface TestWithHelper {
Helper getHelper();
}
where your TestClass will implement it.
Then:
private void getCurrentTestHelper(Object testClass) {
if (testClass instanceof TestWithHelper) {
Helper helper = ((TestWithHelper) testClass).getHelper();
...
}
}