尝试单击存在的并使用PageFactory.initElements（）初始化的按钮时出现NullPointerException

Question

Say, I have two little tests within one class.

public class LoginAndLogout extends BaseTest {

    HomePage kashome = new HomePage();

    @Test(testName = "Login_as")
    public void login() {
        LoginPage loginkas = LoginPage.open(); //open login page
        kashome = loginkas.login(name, pwd);
    }

    @Test
    public void logOut() {
       kashome.logOut();
    }
}

HomePage class:

public class HomePage extends BasePage {

    public HomePage() {
        PageFactory.initElements(Driver.get(), this);
    }
}

BasePage class:

public class BasePage {
    @FindBy(xpath="//img[@title='Выход']")
    WebElement exitButton;

    @FindBy (xpath="//a[text()='Выход']")
    WebElement exitLink;


    public BasePage() {
        PageFactory.initElements(Driver.get(), this);
    }

    public boolean isLoggedIn(String usr) {
        if (this.usernameText.getText().startsWith(usr)) return true;
        else return false;
    }

    public void logOut() {
        try {
            exitLink.click();
            Alert alert = Driver.get().switchTo().alert();
            Reporter.log(alert.getText(), true);
            Reporter.log("Отвечаем ОК", true);
            alert.accept();
        }
        catch (UnhandledAlertException e) {
            e.printStackTrace();
            Reporter.log(e.getMessage(), true);
        }
        catch (Exception e) {
            e.printStackTrace();
            Reporter.log(e.getMessage(), true);
        }
    }

}

1st test runs OK, but on second test I get NPE when trying to execute exitLink.click(), seems like elements in kashome is not initialized, but they are! There is no @AfterTest methods that could affect tests' behavior. I checked button's xpath, it's ok. However, if I add kashome.logOut() to 1st test and delete 2nd one, everything works ok.

Why do I get NPE?

Answer 1

If the PageFactory doesn't process the annotations on exitLink and exitButtons , because those aren't initialized explicitly, they will default to null when your HomePage instance is created.

I think you are assuming that

@FindBy(xpath="//img[@title='Выход']")
WebElement exitButton;

@FindBy (xpath="//a[text()='Выход']")
WebElement exitLink;

because of the @FindBy annotations, will have values when you run your tests. Annotations on their own don't do anything. You need some processor to read them and, through reflection, set the field they are annotating. If PageFactory doesn't do that, those fields will remain null until you set them yourself.