How do you implement Data-Driven Testing in Selenium using TestNG DataProvider and Excel?

<dependency>
    <groupId>org.apache.poi</groupId>
    <artifactId>poi-ooxml</artifactId>
    <version>5.2.5</version>
</dependency>

| scenario | email              | password  | expected         |
|----------|-------------------|-----------|-----------------|
| valid    | alice@test.com    | Pass@123  | Dashboard       |
| invalid  | wrong@test.com    | wrongpass | Invalid credentials |
| empty    |                   |           | Email is required|
| locked   | locked@test.com   | Pass@123  | Account locked  |

// utils/ExcelUtil.java
public class ExcelUtil {

    public static Object[][] readData(String filePath, String sheetName) throws IOException {
        FileInputStream fis       = new FileInputStream(filePath);
        XSSFWorkbook   workbook   = new XSSFWorkbook(fis);
        XSSFSheet      sheet      = workbook.getSheet(sheetName);

        int rowCount = sheet.getLastRowNum();            // skip header row
        int colCount = sheet.getRow(0).getLastCellNum();

        Object[][] data = new Object[rowCount][colCount];

        for (int row = 1; row <= rowCount; row++) {          // start from row 1 (skip header)
            XSSFRow currentRow = sheet.getRow(row);
            for (int col = 0; col < colCount; col++) {
                XSSFCell cell = currentRow.getCell(col);
                data[row - 1][col] = getCellValue(cell);
            }
        }
        workbook.close();
        fis.close();
        return data;
    }

    private static String getCellValue(XSSFCell cell) {
        if (cell == null) return "";
        switch (cell.getCellType()) {
            case STRING:  return cell.getStringCellValue();
            case NUMERIC: return String.valueOf((long) cell.getNumericCellValue());
            case BOOLEAN: return String.valueOf(cell.getBooleanCellValue());
            default:      return "";
        }
    }
}

// tests/LoginTest.java
public class LoginTest extends BaseTest {

    // DataProvider reads from Excel
    @DataProvider(name = "loginData")
    public Object[][] getLoginData() throws IOException {
        return ExcelUtil.readData(
            "src/test/resources/testdata/LoginData.xlsx", "Login");
    }

    @Test(dataProvider = "loginData")
    public void testLogin(String scenario, String email, String pass, String expected) {
        LoginPage login = new LoginPage(DriverManager.getDriver());
        login.login(email, pass);

        if (scenario.equals("valid")) {
            Assert.assertTrue(
                new DashboardPage(DriverManager.getDriver()).isLoaded(),
                "Dashboard not loaded for: " + scenario);
        } else {
            Assert.assertEquals(login.getError(), expected,
                "Error message mismatch for: " + scenario);
        }
    }
}

// For simple cases — hardcoded in test class
@DataProvider(name = "searchTerms")
public Object[][] searchData() {
    return new Object[][] {
        { "Selenium",   true  },
        { "Cypress",    true  },
        { "xyznothing", false },
    };
}

@Test(dataProvider = "searchTerms")
public void testSearch(String term, boolean hasResults) {
    homePage.search(term);
    Assert.assertEquals(resultsPage.hasResults(), hasResults);
}

@DataProvider(name = "usersJson")
public Object[][] getUsersFromJson() throws Exception {
    ObjectMapper mapper = new ObjectMapper();
    JsonNode root = mapper.readTree(new File("src/test/resources/testdata/users.json"));
    Object[][] data = new Object[root.size()][3];
    for (int i = 0; i < root.size(); i++) {
        data[i][0] = root.get(i).get("email").asText();
        data[i][1] = root.get(i).get("password").asText();
        data[i][2] = root.get(i).get("role").asText();
    }
    return data;
}

// Run each data row in parallel (separate threads)
@DataProvider(name = "loginData", parallel = true)
public Object[][] parallelData() throws IOException {
    return ExcelUtil.readData("testdata/login.xlsx", "Sheet1");
}
// Requires ThreadLocal WebDriver in DriverManager!