Validate an email field as the user types, debounced

Wire onModify to a Debouncer so the regular expression validation only runs after the user pauses typing. setInvalid plus setInvalidMessage toggle the field's built-in error state.

import com.webforj.Debouncer;
import com.webforj.component.Composite;
import com.webforj.component.field.TextField;
import com.webforj.component.layout.flexlayout.FlexDirection;
import com.webforj.component.layout.flexlayout.FlexLayout;
import com.webforj.router.annotation.Route;
import java.util.regex.Pattern;

@Route("cookbook-email-validation")
public class DebouncedEmailView extends Composite<FlexLayout> {
  private static final Pattern EMAIL_PATTERN = Pattern.compile("^[^\\s@]+@[^\\s@]+\\.[^\\s@]+$");

  private final FlexLayout self = getBoundComponent();
  private final TextField email = new TextField();
  private final Debouncer debouncer = new Debouncer(0.5f);

  public DebouncedEmailView() {
    self.setDirection(FlexDirection.COLUMN)
        .setMaxWidth("400px")
        .setMargin("var(--dwc-space-xl) auto")
        .setPadding("var(--dwc-space-l)")
        .setSpacing("var(--dwc-space-l)")
        .add(email);

    email
        .setLabel("Email address")
        .setPlaceholder("you@example.com")
        .setHelperText("We'll validate after you pause typing.")
        .onModify(e -> debouncer.run(() -> {
          String value = e.getText();
          if (value.isEmpty()) {
            email.setInvalid(false).setInvalidMessage("");
            return;
          }

          if (EMAIL_PATTERN.matcher(value).matches()) {
            email.setInvalid(false).setInvalidMessage("");
          } else {
            email.setInvalid(true).setInvalidMessage("Enter a valid email address.");
          }
        }));
  }

  @Override
  protected void onDidDestroy() {
    debouncer.cancel();
  }
}

The Debouncer constructor takes seconds as a float (0.5f = 500 ms). Each onModify keystroke calls debouncer.run(...), which cancels the previous pending action and restarts the timer, so the regular expression validation fires only once typing settles. Always cancel the debouncer in onDidDestroy so a pending action can't fire against a destroyed view.