chore: Improve code robustness

vaadincreate-ui/src/main/java/org/vaadin/tatu/vaadincreate/AboutView.java

@@ -26,6 +26,7 @@
 import com.vaadin.ui.HorizontalLayout;
 import com.vaadin.ui.Label;
 import com.vaadin.ui.TextArea;
+import com.vaadin.ui.UI;
 import com.vaadin.ui.VerticalLayout;
 import com.vaadin.ui.themes.ValoTheme;
 
@@ -43,6 +44,8 @@ public class AboutView extends VerticalLayout
     private Label adminsNote;
     private TextArea admionsNoteField;
 
+    private UI ui;
+
     public AboutView() {
         var aboutContent = createAboutContent();
 
@@ -154,7 +157,7 @@ public void enter(ViewChangeEvent event) {
     @Override
     public void eventFired(Object event) {
         if (event instanceof Message) {
-            getUI().access(() -> {
+            Utils.access(ui, () -> {
                 if (admionsNoteField.isVisible()) {
                     admionsNoteField.setVisible(false);
                     adminsNote.setVisible(true);
@@ -168,6 +171,12 @@ public void eventFired(Object event) {
         }
     }
 
+    @Override
+    public void attach() {
+        super.attach();
+        ui = getUI();
+    }
+
     @Override
     public void detach() {
         super.detach();

vaadincreate-ui/src/main/java/org/vaadin/tatu/vaadincreate/auth/BasicAccessControl.java

@@ -18,7 +18,8 @@ public class BasicAccessControl implements AccessControl {
 
     @Override
     public boolean signIn(String username, String password) {
-        Objects.requireNonNull(username, password);
+        Objects.requireNonNull(username);
+        Objects.requireNonNull(password);
         Optional<User> user = VaadinCreateUI.get().getUserService()
                 .findByName(username);
         if (!user.isPresent()) {

vaadincreate-ui/src/main/java/org/vaadin/tatu/vaadincreate/crud/BookGrid.java

@@ -134,6 +134,8 @@ public Product getSelectedRow() {
     }
 
     private String htmlFormatAvailability(Product product) {
+        assert product != null : "Product must not be null";
+
         var availability = product.getAvailability();
         var text = availability.toString();
 
@@ -144,6 +146,8 @@ private String htmlFormatAvailability(Product product) {
     }
 
     private String formatCategories(Product product) {
+        assert product != null : "Product must not be null";
+
         if (product.getCategory() == null || product.getCategory().isEmpty()) {
             return "";
         }
@@ -215,6 +219,8 @@ private void adjustColumns(int width) {
     }
 
     private String createTooltip(Product book) {
+        assert book != null : "Book must not be null";
+
         // This is not actually a tooltip, but on hover popup. Vaadin 8 allows
         // to use HTML in tooltips. which makes it possible to use them like
         // this. When migrating to newer generations of Vaadin, this kind of
@@ -248,6 +254,8 @@ private String createTooltip(Product book) {
 
     // Helper method to create a span with a caption
     private static String getDescriptionCaptionSpan(String caption) {
+        assert caption != null : "Caption must not be null";
+
         return String.format("<span class='%s'>%s:</span> ",
                 VaadinCreateTheme.BOOKVIEW_GRID_DESCRIPTIONCAPTION, caption);
     }

vaadincreate-ui/src/main/java/org/vaadin/tatu/vaadincreate/crud/BooksPresenter.java

@@ -2,6 +2,7 @@
 
 import java.io.Serializable;
 import java.util.Collection;
+import java.util.Objects;
 import java.util.Set;
 import java.util.concurrent.CompletableFuture;
 import java.util.concurrent.ExecutorService;
@@ -165,6 +166,8 @@ public void unlockBook() {
      *            the ID of the book to lock for editing
      */
     private void lockBook(Product book) {
+        assert book != null : "Book must not be null";
+
         if (editing != null) {
             unlockBook();
         }
@@ -192,8 +195,7 @@ public void enter(String productId) {
                 newProduct();
             } else {
                 try {
-                    int pid = Integer.parseInt(productId);
-                    lockAndEditIfExistsAndIsUnlocked(productId, pid);
+                    lockAndEditIfExistsAndIsUnlocked(productId);
                 } catch (NumberFormatException e) {
                     view.showNotValidId(productId);
                     logger.warn("Attempt to edit invalid id '{}'", productId);
@@ -207,7 +209,10 @@ public void enter(String productId) {
     // selected in the view. If the product does not exist, a notification will
     // be shown in the view. If the product exists but is locked, a notification
     // will be shown in the view.
-    private void lockAndEditIfExistsAndIsUnlocked(String productId, int pid) {
+    private void lockAndEditIfExistsAndIsUnlocked(String productId) {
+        assert productId != null;
+
+        int pid = Integer.parseInt(productId);
         Product product = findProduct(pid);
         if (product != null) {
             if (getLockedBooks().isLocked(product) == null) {
@@ -246,9 +251,11 @@ public Product findProduct(int productId) {
      * Saves the given product
      *
      * @param product
-     *            The product to be saved.
+     *            The product to be saved, not null.
      */
     public Product saveProduct(Product product) {
+        Objects.requireNonNull(product, "Product must not be null");
+
         accessControl.assertAdmin();
         view.clearSelection();
         boolean newBook = product.getId() == null;

vaadincreate-ui/src/main/java/org/vaadin/tatu/vaadincreate/crud/BooksView.java

@@ -110,8 +110,12 @@ public BooksView() {
         presenter.init();
     }
 
-    private boolean filterCondition(Object object, String filterText) {
-        return object != null && object.toString().toLowerCase()
+    // Filter the grid data based on the filter text 
+    private static <T> boolean filterCondition(T value, String filterText) {
+        assert filterText != null : "Filter text cannot be null";
+        assert value != null : "Value cannot be null";
+
+        return value != null && value.toString().toLowerCase()
                 .contains(filterText.toLowerCase());
     }
 
@@ -126,6 +130,9 @@ private boolean filterCondition(Object object, String filterText) {
      *         otherwise.
      */
     private boolean passesFilter(Product book, String filterText) {
+        assert filterText != null : "Filter text cannot be null";
+        assert book != null : "Book cannot be null";
+
         filterText = filterText.trim();
         return filterCondition(book.getProductName(), filterText)
                 || filterCondition(book.getAvailability(), filterText)
@@ -422,7 +429,7 @@ public void editProduct(Product product) {
         if (product != null) {
             // Ensure the product is up-to-date
             if (product.getId() != null) {
-                product = refreshProduct(product);
+                product = updateProductInDataProvider(product);
                 if (product == null) {
                     showError(getTranslation(I18n.Books.PRODUCT_DELETED));
                     return;
@@ -549,7 +556,9 @@ private boolean canPush() {
                 && grid.getDataProvider() instanceof ListDataProvider;
     }
 
-    private Product refreshProduct(Product product) {
+    private Product updateProductInDataProvider(Product product) {
+        assert product != null : "Product cannot be null";
+
         var list = ((List<Product>) dataProvider.getItems());
         var updatedProduct = presenter.findProduct(product.getId());
         if (updatedProduct != null) {

vaadincreate-ui/src/main/java/org/vaadin/tatu/vaadincreate/crud/form/BookForm.java

@@ -287,7 +287,7 @@ private void updateDirtyIndicators() {
         });
     }
 
-    private static String convertValue(Object value) {
+    private static <T> String convertValue(T value) {
         if (value == null) {
             return "";
         }

vaadincreate-ui/src/main/java/org/vaadin/tatu/vaadincreate/login/LoginView.java

@@ -161,8 +161,7 @@ private Component buildLoginForm() {
 
         forgotPassword = new Button(getTranslation(I18n.Login.FORGOT_PASSWORD));
         buttons.addComponent(forgotPassword);
-        forgotPassword.addClickListener(event -> showNotification(
-                new Notification(getTranslation(I18n.Login.HINT))));
+        forgotPassword.addClickListener(event -> showHintNotification());
         forgotPassword.addStyleName(ValoTheme.BUTTON_LINK);
 
         lang = new LanguageSelect();
@@ -184,12 +183,12 @@ private Component buildLoginForm() {
     }
 
     private CssLayout buildLoginInformation() {
-        var layout = new CssLayout();
-        layout.setStyleName(VaadinCreateTheme.LOGINVIEW_INFORMATION);
+        var infoLayout = new CssLayout();
+        infoLayout.setStyleName(VaadinCreateTheme.LOGINVIEW_INFORMATION);
         loginInfoText = new Label(getLoginInfoText(), ContentMode.HTML);
         loginInfoText.setSizeFull();
-        layout.addComponent(loginInfoText);
-        return layout;
+        infoLayout.addComponent(loginInfoText);
+        return infoLayout;
     }
 
     // Attempt to log in the user and fire an event to notify listeners.
@@ -198,17 +197,26 @@ private void login() {
                 passwordField.getValue())) {
             fireEvent(new LoginEvent(this));
         } else {
-            showNotification(
-                    new Notification(getTranslation(I18n.Login.LOGIN_FAILED),
-                            getTranslation(I18n.Login.LOGIN_FAILED_DESC),
-                            Notification.Type.HUMANIZED_MESSAGE));
+            showLoginFailedNotification();
             usernameField.focus();
         }
     }
 
-    private void showNotification(Notification notification) {
-        // keep the notification visible a little while after moving the
-        // mouse, or until clicked
+    private void showHintNotification() {
+        var notification = new Notification(getTranslation(I18n.Login.HINT));
+        // keep the notification visible a little while after moving the mouse,
+        // or until clicked
+        notification.setDelayMsec(2000);
+        notification.show(Page.getCurrent());
+    }
+
+    private void showLoginFailedNotification() {
+        var notification = new Notification(
+                getTranslation(I18n.Login.LOGIN_FAILED),
+                getTranslation(I18n.Login.LOGIN_FAILED_DESC),
+                Notification.Type.HUMANIZED_MESSAGE);
+        // keep the notification visible a little while after moving the mouse,
+        // or until clicked
         notification.setDelayMsec(2000);
         notification.show(Page.getCurrent());
     }

vaadincreate-ui/src/main/java/org/vaadin/tatu/vaadincreate/stats/StatsPresenter.java

@@ -29,6 +29,7 @@ public class StatsPresenter implements EventBusListener, Serializable {
 
     private StatsView view;
     private transient CompletableFuture<Void> future;
+    private static final String PRODUCTS_NOT_NULL = "Products must not be null";
 
     public StatsPresenter(StatsView view) {
         this.view = view;
@@ -73,6 +74,7 @@ public void requestUpdateStats() {
     // brackets and product counts
     private Map<String, Long> calculatePriceStats(
             Collection<Product> products) {
+        assert products != null : PRODUCTS_NOT_NULL;
         return getPriceBrackets(products).stream()
                 .collect(Collectors.toMap(PriceBracket::toString,
                         priceBracket -> products.stream()
@@ -85,6 +87,7 @@ private Map<String, Long> calculatePriceStats(
     // category names and product counts
     private Map<String, Long[]> calculateCategoryStats(
             ProductDataService service, Collection<Product> products) {
+        assert products != null : PRODUCTS_NOT_NULL;
         return service.getAllCategories().stream()
                 .collect(Collectors.toMap(Category::getName, category -> {
                     long titles = products.stream().filter(
@@ -101,6 +104,7 @@ private Map<String, Long[]> calculateCategoryStats(
     // availability statuses and product counts
     private Map<Availability, Long> calculateAvailabilityStats(
             Collection<Product> products) {
+        assert products != null : PRODUCTS_NOT_NULL;
         return Arrays.stream(Availability.values()).map(availability -> Map
                 .entry(availability, products.stream().filter(
                         product -> product.getAvailability() == availability)
@@ -118,6 +122,8 @@ public void cancelUpdateStats() {
     }
 
     private List<PriceBracket> getPriceBrackets(Collection<Product> products) {
+        assert products != null : PRODUCTS_NOT_NULL;
+
         var brackets = new ArrayList<PriceBracket>();
         var max = products.stream()
                 .max((p1, p2) -> p1.getPrice().compareTo(p2.getPrice())).get()

vaadincreate-ui/src/main/java/org/vaadin/tatu/vaadincreate/stats/StatsView.java

@@ -116,6 +116,7 @@ private CssLayout createAvailabilityChart() {
     }
 
     private static void configureTooltip(Configuration conf) {
+        assert conf != null : "Configuration must not be null";
         conf.getTooltip()
                 .setBackgroundColor(new SolidColor("rgba(50,50,50,0.9)"));
         conf.getTooltip().getStyle().setColor(new SolidColor("white"));
@@ -152,6 +153,8 @@ public void updateStatsAsync(Map<Availability, Long> availabilityStats,
 
     // Update the charts with the new data
     private void updatePriceChart(Map<String, Long> priceStats) {
+        assert priceStats != null : "Price stats must not be null";
+
         var priceSeries = priceSeries(priceStats);
         priceSeries.setName(getTranslation(I18n.Stats.COUNT));
         var conf = priceChart.getConfiguration();
@@ -160,6 +163,7 @@ private void updatePriceChart(Map<String, Long> priceStats) {
 
     // Update the charts with the new data
     private void updateCategoryChart(Map<String, Long[]> categoryStats) {
+        assert categoryStats != null : "Category stats must not be null";
         var conf = categoryChart.getConfiguration();
 
         // Show count of titles on primary axis
@@ -185,6 +189,8 @@ private void updateCategoryChart(Map<String, Long[]> categoryStats) {
     // Update the charts with the new data
     private void updateAvailabilityChart(
             Map<Availability, Long> availabilityStats) {
+        assert availabilityStats != null : "Availability stats must not be null";
+
         var availabilitySeries = availabilitySeries(availabilityStats);
         availabilitySeries.setName(getTranslation(I18n.Stats.COUNT));
         var conf = availabilityChart.getConfiguration();
@@ -198,6 +204,8 @@ private void updateAvailabilityChart(
 
     private DataSeries categorySeries(Map<String, Long[]> categories,
             int index) {
+        assert categories != null : "Categories must not be null";
+
         var series = new DataSeries();
         categories.forEach((category, count) -> {
             var item = new DataSeriesItem(category, count[index]);
@@ -209,6 +217,8 @@ private DataSeries categorySeries(Map<String, Long[]> categories,
 
     private DataSeries availabilitySeries(
             Map<Availability, Long> availabilities) {
+        assert availabilities != null : "Availabilities must not be null";
+
         var series = new DataSeries();
         availabilities.forEach((availability, count) -> {
             var item = new DataSeriesItem(availability.name(), count);
@@ -220,6 +230,8 @@ private DataSeries availabilitySeries(
     }
 
     private static SolidColor toColor(Availability availability) {
+        assert availability != null : "Availability must not be null";
+
         String color;
         switch (availability) {
         case COMING:
@@ -236,6 +248,8 @@ private static SolidColor toColor(Availability availability) {
     }
 
     private DataSeries priceSeries(Map<String, Long> prices) {
+        assert prices != null : "Prices must not be null";
+
         var series = new DataSeries();
         prices.forEach((pricebracket, count) -> {
             var item = new DataSeriesItem(pricebracket, count);