Add interface for AppWidgetset (#19770)

This allows selecting the widgetset name and URL simply by placing
a class in the default package if nothing is explicitly give by
the user. This can be used e.g. by the Maven plug-in and other build
automation tools to automatically generate widgetsets or use one
from CDN.

Change-Id: If3a7b35e3b25371e08e6d9b504fcda6f66de5119

6 files changed, 264 insertions, 43 deletions

diff --git a/all/src/main/templates/release-notes.html b/all/src/main/templates/release-notes.html
index b9dcc9774b..6c522ef4d6 100644
--- a/all/src/main/templates/release-notes.html
+++ b/all/src/main/templates/release-notes.html
@@ -112,6 +112,7 @@
         <ul>
             <li>Vaadin artifacts no longer bring a transitive dependency to javax.servlet:servlet-api.</li>
             <li>System properties now override application parameters for settings such as production mode (see above).</li>
+            <li>The return type of UIProvider.getWidgetset() and BootstrapHandler.getWidgetsetForUI() has changed.</li>
         </ul>
         <h3 id="knownissues">Known Issues and Limitations</h3>
         <ul>
diff --git a/server/src/main/java/com/vaadin/server/BootstrapHandler.java b/server/src/main/java/com/vaadin/server/BootstrapHandler.java
index a9343a7e03..b766dfc92c 100644
--- a/server/src/main/java/com/vaadin/server/BootstrapHandler.java
+++ b/server/src/main/java/com/vaadin/server/BootstrapHandler.java
@@ -55,10 +55,10 @@ import elemental.json.JsonObject;
 import elemental.json.impl.JsonUtil;
 
 /**
- * 
+ *
  * @author Vaadin Ltd
  * @since 7.0.0
- * 
+ *
  * @deprecated As of 7.0. Will likely change or be removed in a future version
  */
 @Deprecated
@@ -76,12 +76,12 @@ public abstract class BootstrapHandler extends SynchronizedRequestHandler {
         private final VaadinResponse response;
         private final BootstrapFragmentResponse bootstrapResponse;
 
-        private String widgetsetName;
         private String themeName;
         private String appId;
         private PushMode pushMode;
         private JsonObject applicationParameters;
         private VaadinUriResolver uriResolver;
+        private WidgetsetInfo widgetsetInfo;
 
         public BootstrapContext(VaadinResponse response,
                 BootstrapFragmentResponse bootstrapResponse) {
@@ -105,11 +105,20 @@ public abstract class BootstrapHandler extends SynchronizedRequestHandler {
             return bootstrapResponse.getUiClass();
         }
 
-        public String getWidgetsetName() {
-            if (widgetsetName == null) {
-                widgetsetName = getWidgetsetForUI(this);
+        public WidgetsetInfo getWidgetsetInfo() {
+            if (widgetsetInfo == null) {
+                widgetsetInfo = getWidgetsetForUI(this);
             }
-            return widgetsetName;
+            return widgetsetInfo;
+        }
+
+        /**
+         * @return returns the name of the widgetset to use
+         * @deprecated use {@link #getWidgetsetInfo()} instead
+         */
+        @Deprecated
+        public String getWidgetsetName() {
+            return getWidgetsetInfo().getWidgetsetName();
         }
 
         public String getThemeName() {
@@ -455,18 +464,19 @@ public abstract class BootstrapHandler extends SynchronizedRequestHandler {
         return null;
     }
 
-    public String getWidgetsetForUI(BootstrapContext context) {
+    public WidgetsetInfo getWidgetsetForUI(BootstrapContext context) {
         VaadinRequest request = context.getRequest();
 
         UICreateEvent event = new UICreateEvent(context.getRequest(),
                 context.getUIClass());
-        String widgetset = context.getBootstrapResponse().getUIProvider()
-                .getWidgetset(event);
+        WidgetsetInfo widgetset = context.getBootstrapResponse()
+                .getUIProvider().getWidgetset(event);
         if (widgetset == null) {
-            widgetset = request.getService().getConfiguredWidgetset(request);
+            // TODO do we want to move WidgetsetInfoImpl elsewhere?
+            widgetset = new WidgetsetInfoImpl(request.getService()
+                    .getConfiguredWidgetset(request));
         }
 
-        widgetset = VaadinServlet.stripSpecialChars(widgetset);
         return widgetset;
     }
 
@@ -477,9 +487,9 @@ public abstract class BootstrapHandler extends SynchronizedRequestHandler {
      * Override this method if you want to add some custom html around around
      * the div element into which the actual Vaadin application will be
      * rendered.
-     * 
+     *
      * @param context
-     * 
+     *
      * @throws IOException
      */
     private void setupMainDiv(BootstrapContext context) throws IOException {
@@ -618,7 +628,15 @@ public abstract class BootstrapHandler extends SynchronizedRequestHandler {
         }
 
         appConfig.put("versionInfo", versionInfo);
-        appConfig.put("widgetset", context.getWidgetsetName());
+
+        WidgetsetInfo widgetsetInfo = context.getWidgetsetInfo();
+        appConfig.put("widgetset", VaadinServlet
+                .stripSpecialChars(widgetsetInfo.getWidgetsetName()));
+        // add widgetset url if not null
+        if (widgetsetInfo.getWidgetsetUrl() != null) {
+            appConfig.put("widgetsetUrl", widgetsetInfo.getWidgetsetUrl());
+        }
+        appConfig.put("widgetsetReady", !widgetsetInfo.isCdn());
 
         // Use locale from session if set, else from the request
         Locale locale = ServletPortletHelper.findLocale(null,
@@ -694,13 +712,13 @@ public abstract class BootstrapHandler extends SynchronizedRequestHandler {
 
     /**
      * Get the URI for the application theme.
-     * 
+     *
      * A portal-wide default theme is fetched from the portal shared resource
      * directory (if any), other themes from the portlet.
-     * 
+     *
      * @param context
      * @param themeName
-     * 
+     *
      * @return
      */
     public String getThemeUri(BootstrapContext context, String themeName) {
@@ -713,7 +731,7 @@ public abstract class BootstrapHandler extends SynchronizedRequestHandler {
 
     /**
      * Override if required
-     * 
+     *
      * @param context
      * @return
      */
@@ -725,7 +743,7 @@ public abstract class BootstrapHandler extends SynchronizedRequestHandler {
 
     /**
      * Do not override.
-     * 
+     *
      * @param context
      * @return
      */
diff --git a/server/src/main/java/com/vaadin/server/UIProvider.java b/server/src/main/java/com/vaadin/server/UIProvider.java
index 7fd880919e..9b0087185b 100644
--- a/server/src/main/java/com/vaadin/server/UIProvider.java
+++ b/server/src/main/java/com/vaadin/server/UIProvider.java
@@ -1,12 +1,12 @@
 /*
  * Copyright 2000-2014 Vaadin Ltd.
- * 
+ *
  * Licensed under the Apache License, Version 2.0 (the "License"); you may not
  * use this file except in compliance with the License. You may obtain a copy of
  * the License at
- * 
+ *
  * http://www.apache.org/licenses/LICENSE-2.0
- * 
+ *
  * Unless required by applicable law or agreed to in writing, software
  * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
  * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
@@ -20,6 +20,8 @@ import java.io.InputStream;
 import java.io.Serializable;
 import java.lang.annotation.Annotation;
 import java.lang.annotation.Inherited;
+import java.util.logging.Level;
+import java.util.logging.Logger;
 
 import com.vaadin.annotations.PreserveOnRefresh;
 import com.vaadin.annotations.Push;
@@ -58,7 +60,7 @@ public abstract class UIProvider implements Serializable {
      * do not follow the standard semantics and are supported for backwards
      * compatibility. Future versions of the framework might only support the
      * standard semantics of {@code @Inherited}.
-     * 
+     *
      * @param clazz
      *            the class from which the annotation should be found
      * @param annotationType
@@ -104,13 +106,13 @@ public abstract class UIProvider implements Serializable {
      * <p>
      * The default implementation checks for a @{@link Theme} annotation on the
      * UI class.
-     * 
+     *
      * @param event
      *            the UI create event with information about the UI and the
      *            current request.
      * @return the name of the theme, or <code>null</code> if the default theme
      *         should be used
-     * 
+     *
      */
     public String getTheme(UICreateEvent event) {
         Theme uiTheme = getAnnotationFor(event.getUIClass(), Theme.class);
@@ -125,26 +127,90 @@ public abstract class UIProvider implements Serializable {
      * Finds the widgetset to use for a specific UI. If no specific widgetset is
      * required, <code>null</code> is returned.
      * <p>
-     * The default implementation uses the @{@link Widgetset} annotation if it's
-     * defined for the UI class.
-     * 
+     * The default implementation uses the following order of priority for
+     * finding the widgetset information:
+     * <ul>
+     * <li>@{@link Widgetset} annotation if it is defined for the UI class</li>
+     * <li>The class AppWidgetset if one exists in the default package</li>
+     * <li>A widgetset called AppWidgetset if there is an AppWidgetset.gwt.xml
+     * file in the default package</li>
+     * <li>null to use the default widgetset otherwise</li>
+     * </ul>
+     *
+     * Note that the return type of this method changed in Vaadin 7.7.
+     *
      * @param event
      *            the UI create event with information about the UI and the
      *            current request.
      * @return the name of the widgetset, or <code>null</code> if the default
      *         widgetset should be used
-     * 
+     *
+     * @since 7.7
      */
-    public String getWidgetset(UICreateEvent event) {
+    public WidgetsetInfo getWidgetset(UICreateEvent event) {
         Widgetset uiWidgetset = getAnnotationFor(event.getUIClass(),
                 Widgetset.class);
+
+        // First case: We have an @Widgetset annotation, use that
         if (uiWidgetset != null) {
-            return uiWidgetset.value();
-        } else {
+            return new WidgetsetInfoImpl(uiWidgetset.value());
+        }
+
+        // Find the class AppWidgetset in the default package if one exists
+        WidgetsetInfo info = getWidgetsetClassInfo();
+
+        // Second case: we have a generated class called APP_WIDGETSET_NAME
+        if (info != null) {
+            return info;
+        }
+
+        // third case: we have an AppWidgetset.gwt.xml file
+        else {
             InputStream resource = event.getUIClass().getResourceAsStream(
                     "/" + APP_WIDGETSET_NAME + ".gwt.xml");
             if (resource != null) {
-                return APP_WIDGETSET_NAME;
+                return new WidgetsetInfoImpl(false, null, APP_WIDGETSET_NAME);
+            }
+        }
+
+        // fourth case: we are using the default widgetset
+        return null;
+    }
+
+    private Class<WidgetsetInfo> findWidgetsetClass() {
+        try {
+            // We cannot naively use Class.forname without getting the correct
+            // classloader
+            // FIXME This might still fail with osgi
+            ClassLoader tccl = VaadinService.getCurrent().getClassLoader();
+            Class<?> c = Class.forName(APP_WIDGETSET_NAME, true, tccl);
+
+            // if not implementing the interface, possibly a @WebListener class
+            // from an earlier version - ignore it
+            if (WidgetsetInfo.class.isAssignableFrom(c)) {
+                return (Class<WidgetsetInfo>) c;
+            }
+        } catch (ClassNotFoundException e) {
+            // ClassNotFound is a normal case
+        }
+        return null;
+    }
+
+    private WidgetsetInfo getWidgetsetClassInfo() {
+        Class<WidgetsetInfo> cls = findWidgetsetClass();
+        if (cls != null) {
+            try {
+                return cls.newInstance();
+            } catch (InstantiationException e) {
+                getLogger().log(
+                        Level.INFO,
+                        "Unexpected trying to instantiate class "
+                                + cls.getName(), e);
+            } catch (IllegalAccessException e) {
+                getLogger()
+                        .log(Level.INFO,
+                                "Unexpected trying to access class "
+                                        + cls.getName(), e);
             }
         }
         return null;
@@ -159,12 +225,12 @@ public abstract class UIProvider implements Serializable {
      * Whenever a preserved UI is reused, its
      * {@link UI#refresh(com.vaadin.server.VaadinRequest) refresh} method is
      * invoked by the framework first.
-     * 
-     * 
+     *
+     *
      * @param event
      *            the UI create event with information about the UI and the
      *            current request.
-     * 
+     *
      * @return <code>true</code>if the same UI instance should be reused e.g.
      *         when the browser window is refreshed.
      */
@@ -190,13 +256,13 @@ public abstract class UIProvider implements Serializable {
      * <p>
      * The default implementation uses the @{@link Push} annotation if it's
      * defined for the UI class.
-     * 
+     *
      * @param event
      *            the UI create event with information about the UI and the
      *            current request.
      * @return the push mode to use, or <code>null</code> if the default push
      *         mode should be used
-     * 
+     *
      */
     public PushMode getPushMode(UICreateEvent event) {
         Push push = getAnnotationFor(event.getUIClass(), Push.class);
@@ -213,7 +279,7 @@ public abstract class UIProvider implements Serializable {
      * <p>
      * The default implementation uses the @{@link Push} annotation if it's
      * defined for the UI class.
-     * 
+     *
      * @param event
      *            the UI create event with information about the UI and the
      *            current request.
@@ -229,4 +295,8 @@ public abstract class UIProvider implements Serializable {
         }
     }
 
+    private static final Logger getLogger() {
+        return Logger.getLogger(UIProvider.class.getName());
+    }
+
 }
diff --git a/server/src/main/java/com/vaadin/server/WidgetsetInfo.java b/server/src/main/java/com/vaadin/server/WidgetsetInfo.java
new file mode 100644
index 0000000000..fd62b0b309
--- /dev/null
+++ b/server/src/main/java/com/vaadin/server/WidgetsetInfo.java
@@ -0,0 +1,57 @@
+/*
+ * Copyright 2000-2014 Vaadin Ltd.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License"); you may not
+ * use this file except in compliance with the License. You may obtain a copy of
+ * the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+ * License for the specific language governing permissions and limitations under
+ * the License.
+ */
+
+package com.vaadin.server;
+
+import java.io.Serializable;
+
+/**
+ * An interface describing the widgetset that the client should try to load.
+ * <p>
+ * In addition to explicit use within the framework, adding a class called
+ * AppWidgetset implementing this interface in the default package will
+ * configure the widgetset to use unless the user has explicitly selected a
+ * different widgetset. See {@link BootstrapHandler} and {@link UIProvider} for
+ * more information.
+ *
+ * @since 7.7
+ */
+public interface WidgetsetInfo extends Serializable {
+
+    /**
+     * Returns the name of the widgetset to use.
+     *
+     * @return widgetset name
+     */
+    public String getWidgetsetName();
+
+    /**
+     * Returns the widgetset URL. Can be null for local widgetsets at default
+     * location.
+     *
+     * @return widgetset URL or null for client generated URL
+     */
+    public String getWidgetsetUrl();
+
+    /**
+     * If cdn is true, the client side should wait if it didn't manage to load
+     * the widgetset, as it might still be compiling.
+     *
+     * @return true to wait and retry if the widgetset could not be loaded
+     */
+    public boolean isCdn();
+
+}
diff --git a/server/src/main/java/com/vaadin/server/WidgetsetInfoImpl.java b/server/src/main/java/com/vaadin/server/WidgetsetInfoImpl.java
new file mode 100644
index 0000000000..a887b0b7ac
--- /dev/null
+++ b/server/src/main/java/com/vaadin/server/WidgetsetInfoImpl.java
@@ -0,0 +1,65 @@
+/*
+ * Copyright 2000-2014 Vaadin Ltd.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License"); you may not
+ * use this file except in compliance with the License. You may obtain a copy of
+ * the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+ * License for the specific language governing permissions and limitations under
+ * the License.
+ */
+
+package com.vaadin.server;
+
+/**
+ * Default implementation of {@link WidgetsetInfo} that is used for internal
+ * communication between the parts of the framework.
+ * <p>
+ * Class needs to be static so that it can be easily used in e.g.
+ * BootstrapHandler.
+ * <p>
+ * This class is intended primarily for internal use. It is recommended to
+ * implement WidgetsetInfo directly rather than extending or using this
+ * class outside the framework, and this class is subject to changes.
+ *
+ * @since 7.7
+ */
+class WidgetsetInfoImpl implements WidgetsetInfo {
+
+    private final boolean cdn;
+    private final String widgetsetUrl;
+    private final String widgetsetName;
+
+    public WidgetsetInfoImpl(boolean cdn, String widgetsetUrl,
+            String widgetsetName) {
+
+        this.cdn = cdn;
+        this.widgetsetUrl = widgetsetUrl;
+        this.widgetsetName = widgetsetName;
+    }
+
+    public WidgetsetInfoImpl(String widgetsetName) {
+        this(false, null, widgetsetName);
+    }
+
+    @Override
+    public boolean isCdn() {
+        return cdn;
+    }
+
+    @Override
+    public String getWidgetsetUrl() {
+        return widgetsetUrl;
+    }
+
+    @Override
+    public String getWidgetsetName() {
+        return widgetsetName;
+    }
+
+}
\ No newline at end of file
diff --git a/server/src/main/resources/VAADIN/vaadinBootstrap.js b/server/src/main/resources/VAADIN/vaadinBootstrap.js
index 89514dbcc2..a33884eee3 100644
--- a/server/src/main/resources/VAADIN/vaadinBootstrap.js
+++ b/server/src/main/resources/VAADIN/vaadinBootstrap.js
@@ -41,14 +41,23 @@
 		return (typeof window[className]) != "undefined";
 	};
 	
-	var loadWidgetset = function(url, widgetset) {
+	var loadWidgetset = function(url, widgetset, ready) {
 		if (widgetsets[widgetset]) {
 			return;
 		}
 		log("load widgetset", url, widgetset);
 		setTimeout(function() {
 			if (!isWidgetsetLoaded(widgetset)) {
-				alert("Failed to load the widgetset: " + url);
+				if (ready) {
+					alert("Failed to load the widgetset: " + url);
+				} else {
+					if (window.confirm("Failed to load the widgetset. If using CDN for the widgetset, it is possible that compiling it takes up to a few minutes. Would you like to try again?")) {
+						window[widgetset] = undefined;
+						window.location.reload(false);
+					} else {
+						alert("Failed to load the widgetset: " + url);
+					}
+				}
 			}
 		}, 15000);
 	
@@ -216,7 +225,8 @@
 				if (!widgetsetUrl) {
 					widgetsetUrl = vaadinDir + 'widgetsets/' + widgetset + "/" + widgetset + ".nocache.js?" + new Date().getTime();
 				}
-				loadWidgetset(widgetsetUrl, widgetset);
+				var widgetsetReady = getConfig('widgetsetReady');
+				loadWidgetset(widgetsetUrl, widgetset, widgetsetReady);
 				
 				if (getConfig('uidl') === undefined) {
 					if (mayDefer) {