How does PageFactory work and what are its pitfalls?

PageFactory is a convenience layer for page objects. Instead of writing findElement in every method, you declare a field and annotate it. initElements creates the proxies. The element is not found at construction time; it is located when the field is first used.

public class LoginPage {
    @FindBy(id = "email")
    private WebElement email;

    @FindBy(css = "[data-testid='sign-in']")
    private WebElement signIn;

    public LoginPage(WebDriver driver) {
        PageFactory.initElements(driver, this);
    }

    public void signIn(String user) {
        email.sendKeys(user);
        signIn.click();
    }
}

• initElements must be called before the fields are used
• Proxies re-locate on each use, which can reduce stale element failures
• @CacheLookup caches the element after the first lookup and can go stale after re-renders
• An AjaxElementLocatorFactory adds a lazy wait to the proxy lookup
• PageFactory does not make a bad locator stable; it only changes when the lookup happens
• Modern teams often prefer explicit By fields or a component library instead of annotations

The most common bug is combining PageFactory with a driver that changes between tests while reusing a cached page object. Another is assuming the field is resolved at construction, then checking for a missing element in the constructor. Be explicit about when lookup happens.