Code cleanup: Move dependency loading logic to a separate class (#8290)

4 files changed, 186 insertions, 88 deletions

diff --git a/client/src/main/java/com/vaadin/client/ApplicationConfiguration.java b/client/src/main/java/com/vaadin/client/ApplicationConfiguration.java
index 102dc15761..e599eef61b 100644
--- a/client/src/main/java/com/vaadin/client/ApplicationConfiguration.java
+++ b/client/src/main/java/com/vaadin/client/ApplicationConfiguration.java
@@ -624,14 +624,18 @@ public class ApplicationConfiguration implements EntryPoint {
     }
 
     /**
+     * Runs the given command when all pending dependencies have been loaded, or
+     * immediately if no dependencies are being loaded.
+     *
      * @since 7.6
-     * @param c
+     * @param command
+     *            the command to run
      */
-    public static void runWhenDependenciesLoaded(Command c) {
+    public static void runWhenDependenciesLoaded(Command command) {
         if (dependenciesLoading == 0) {
-            c.execute();
+            command.execute();
         } else {
-            callbacks.add(c);
+            callbacks.add(command);
         }
     }
 
diff --git a/client/src/main/java/com/vaadin/client/ApplicationConnection.java b/client/src/main/java/com/vaadin/client/ApplicationConnection.java
index 1fe1f83cb1..9d9a66173d 100644
--- a/client/src/main/java/com/vaadin/client/ApplicationConnection.java
+++ b/client/src/main/java/com/vaadin/client/ApplicationConnection.java
@@ -26,7 +26,6 @@ import com.google.gwt.aria.client.Roles;
 import com.google.gwt.core.client.Duration;
 import com.google.gwt.core.client.GWT;
 import com.google.gwt.core.client.JavaScriptObject;
-import com.google.gwt.core.client.JsArrayString;
 import com.google.gwt.core.client.Scheduler;
 import com.google.gwt.dom.client.Element;
 import com.google.gwt.event.shared.EventBus;
@@ -42,8 +41,6 @@ import com.google.gwt.user.client.Timer;
 import com.google.gwt.user.client.ui.HasWidgets;
 import com.google.gwt.user.client.ui.Widget;
 import com.vaadin.client.ApplicationConfiguration.ErrorMessage;
-import com.vaadin.client.ResourceLoader.ResourceLoadEvent;
-import com.vaadin.client.ResourceLoader.ResourceLoadListener;
 import com.vaadin.client.communication.ConnectionStateHandler;
 import com.vaadin.client.communication.Heartbeat;
 import com.vaadin.client.communication.MessageHandler;
@@ -387,6 +384,7 @@ public class ApplicationConnection implements HasHandlers {
         serverRpcQueue.setConnection(this);
         messageHandler.setConnection(this);
         messageSender.setConnection(this);
+        dependencyLoader.setConnection(this);
 
         ComponentLocator componentLocator = new ComponentLocator(this);
 
@@ -765,79 +763,6 @@ public class ApplicationConnection implements HasHandlers {
         return getLoadingIndicator().isVisible();
     }
 
-    public void loadStyleDependencies(JsArrayString dependencies) {
-        // Assuming no reason to interpret in a defined order
-        ResourceLoadListener resourceLoadListener = new ResourceLoadListener() {
-            @Override
-            public void onLoad(ResourceLoadEvent event) {
-                ApplicationConfiguration.endDependencyLoading();
-            }
-
-            @Override
-            public void onError(ResourceLoadEvent event) {
-                getLogger().severe(event.getResourceUrl()
-                        + " could not be loaded, or the load detection failed because the stylesheet is empty.");
-                // The show must go on
-                onLoad(event);
-            }
-        };
-        ResourceLoader loader = ResourceLoader.get();
-        for (int i = 0; i < dependencies.length(); i++) {
-            String url = translateVaadinUri(dependencies.get(i));
-            ApplicationConfiguration.startDependencyLoading();
-            loader.loadStylesheet(url, resourceLoadListener);
-        }
-    }
-
-    public void loadScriptDependencies(final JsArrayString dependencies) {
-        if (dependencies.length() == 0) {
-            return;
-        }
-
-        // Listener that loads the next when one is completed
-        ResourceLoadListener resourceLoadListener = new ResourceLoadListener() {
-            @Override
-            public void onLoad(ResourceLoadEvent event) {
-                if (dependencies.length() != 0) {
-                    String url = translateVaadinUri(dependencies.shift());
-                    ApplicationConfiguration.startDependencyLoading();
-                    // Load next in chain (hopefully already preloaded)
-                    event.getResourceLoader().loadScript(url, this);
-                }
-                // Call start for next before calling end for current
-                ApplicationConfiguration.endDependencyLoading();
-            }
-
-            @Override
-            public void onError(ResourceLoadEvent event) {
-                getLogger().severe(
-                        event.getResourceUrl() + " could not be loaded.");
-                // The show must go on
-                onLoad(event);
-            }
-        };
-
-        ResourceLoader loader = ResourceLoader.get();
-
-        // Start chain by loading first
-        String url = translateVaadinUri(dependencies.shift());
-        ApplicationConfiguration.startDependencyLoading();
-        loader.loadScript(url, resourceLoadListener);
-
-        if (ResourceLoader.supportsInOrderScriptExecution()) {
-            for (int i = 0; i < dependencies.length(); i++) {
-                String preloadUrl = translateVaadinUri(dependencies.get(i));
-                loader.loadScript(preloadUrl, null);
-            }
-        } else {
-            // Preload all remaining
-            for (int i = 0; i < dependencies.length(); i++) {
-                String preloadUrl = translateVaadinUri(dependencies.get(i));
-                loader.preloadResource(preloadUrl, null);
-            }
-        }
-    }
-
     private void addVariableToQueue(String connectorId, String variableName,
             Object value, boolean immediate) {
         boolean lastOnly = !immediate;
@@ -1280,6 +1205,9 @@ public class ApplicationConnection implements HasHandlers {
 
     private ConnectorMap connectorMap = GWT.create(ConnectorMap.class);
 
+    private final DependencyLoader dependencyLoader = GWT
+            .create(DependencyLoader.class);
+
     /**
      * Use to notify that the given component's caption has changed; layouts may
      * have to be recalculated.
@@ -1636,4 +1564,13 @@ public class ApplicationConnection implements HasHandlers {
         return getMessageHandler().getLastSeenServerSyncId();
     }
 
+    /**
+     * Gets the instance which handles loading of dependencies.
+     *
+     * @return the dependency loader for this connection
+     */
+    public DependencyLoader getDependencyLoader() {
+        return dependencyLoader;
+    }
+
 }
diff --git a/client/src/main/java/com/vaadin/client/DependencyLoader.java b/client/src/main/java/com/vaadin/client/DependencyLoader.java
new file mode 100644
index 0000000000..c644cd87db
--- /dev/null
+++ b/client/src/main/java/com/vaadin/client/DependencyLoader.java
@@ -0,0 +1,164 @@
+/*
+ * Copyright 2000-2016 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.client;
+
+import java.util.logging.Logger;
+
+import com.google.gwt.core.client.JsArrayString;
+import com.google.gwt.user.client.Command;
+import com.vaadin.client.ResourceLoader.ResourceLoadEvent;
+import com.vaadin.client.ResourceLoader.ResourceLoadListener;
+
+/**
+ * Handles loading of dependencies (style sheets and scripts) in the
+ * application.
+ *
+ * Use {@link ApplicationConfiguration#runWhenDependenciesLoaded(Command)} to
+ * execute a command after all dependencies have finished loading.
+ *
+ * @author Vaadin Ltd
+ * @since 8.0.0
+ */
+public class DependencyLoader {
+
+    private static final String STYLE_DEPENDENCIES = "styleDependencies";
+    private static final String SCRIPT_DEPENDENCIES = "scriptDependencies";
+    private ApplicationConnection connection = null;
+
+    /**
+     * Sets the ApplicationConnection this instance is connected to.
+     *
+     * Only used internally.
+     *
+     * @param connection
+     *            The ApplicationConnection for this instance
+     */
+    public void setConnection(ApplicationConnection connection) {
+        if (this.connection != null) {
+            throw new IllegalStateException(
+                    "Application connection has already been set");
+        }
+        if (connection == null) {
+            throw new IllegalArgumentException(
+                    "ApplicationConnection can not be null");
+        }
+        this.connection = connection;
+    }
+
+    /**
+     * Loads the any dependencies present in the given json snippet.
+     *
+     * Scans the key "{@literal scriptDependencies}" for JavaScripts and the key
+     * "{@literal styleDependencies}" for style sheets.
+     *
+     * Ensures that the given JavaScript dependencies are loaded in the given
+     * order. Does not ensure anything about stylesheet order.
+     *
+     * @param json
+     *            the JSON containing the dependencies to load
+     */
+    public void loadDependencies(ValueMap json) {
+        if (json.containsKey(SCRIPT_DEPENDENCIES)) {
+            loadScriptDependencies(json.getJSStringArray(SCRIPT_DEPENDENCIES));
+        }
+        if (json.containsKey(STYLE_DEPENDENCIES)) {
+            loadStyleDependencies(json.getJSStringArray(STYLE_DEPENDENCIES));
+        }
+
+    }
+
+    private void loadStyleDependencies(JsArrayString dependencies) {
+        // Assuming no reason to interpret in a defined order
+        ResourceLoadListener resourceLoadListener = new ResourceLoadListener() {
+            @Override
+            public void onLoad(ResourceLoadEvent event) {
+                ApplicationConfiguration.endDependencyLoading();
+            }
+
+            @Override
+            public void onError(ResourceLoadEvent event) {
+                getLogger().severe(event.getResourceUrl()
+                        + " could not be loaded, or the load detection failed because the stylesheet is empty.");
+                // The show must go on
+                onLoad(event);
+            }
+        };
+        ResourceLoader loader = ResourceLoader.get();
+        for (int i = 0; i < dependencies.length(); i++) {
+            String url = translateVaadinUri(dependencies.get(i));
+            ApplicationConfiguration.startDependencyLoading();
+            loader.loadStylesheet(url, resourceLoadListener);
+        }
+    }
+
+    private void loadScriptDependencies(final JsArrayString dependencies) {
+        if (dependencies.length() == 0) {
+            return;
+        }
+
+        // Listener that loads the next when one is completed
+        ResourceLoadListener resourceLoadListener = new ResourceLoadListener() {
+            @Override
+            public void onLoad(ResourceLoadEvent event) {
+                if (dependencies.length() != 0) {
+                    String url = translateVaadinUri(dependencies.shift());
+                    ApplicationConfiguration.startDependencyLoading();
+                    // Load next in chain (hopefully already preloaded)
+                    event.getResourceLoader().loadScript(url, this);
+                }
+                // Call start for next before calling end for current
+                ApplicationConfiguration.endDependencyLoading();
+            }
+
+            @Override
+            public void onError(ResourceLoadEvent event) {
+                getLogger().severe(
+                        event.getResourceUrl() + " could not be loaded.");
+                // The show must go on
+                onLoad(event);
+            }
+        };
+
+        ResourceLoader loader = ResourceLoader.get();
+
+        // Start chain by loading first
+        String url = translateVaadinUri(dependencies.shift());
+        ApplicationConfiguration.startDependencyLoading();
+        loader.loadScript(url, resourceLoadListener);
+
+        if (ResourceLoader.supportsInOrderScriptExecution()) {
+            for (int i = 0; i < dependencies.length(); i++) {
+                String preloadUrl = translateVaadinUri(dependencies.get(i));
+                loader.loadScript(preloadUrl, null);
+            }
+        } else {
+            // Preload all remaining
+            for (int i = 0; i < dependencies.length(); i++) {
+                String preloadUrl = translateVaadinUri(dependencies.get(i));
+                loader.preloadResource(preloadUrl, null);
+            }
+        }
+    }
+
+    private String translateVaadinUri(String url) {
+        return connection.translateVaadinUri(url);
+    }
+
+    private static Logger getLogger() {
+        return Logger.getLogger(DependencyLoader.class.getName());
+    }
+
+}
diff --git a/client/src/main/java/com/vaadin/client/communication/MessageHandler.java b/client/src/main/java/com/vaadin/client/communication/MessageHandler.java
index a8e22ea53b..5057d574fa 100644
--- a/client/src/main/java/com/vaadin/client/communication/MessageHandler.java
+++ b/client/src/main/java/com/vaadin/client/communication/MessageHandler.java
@@ -382,14 +382,7 @@ public class MessageHandler {
         }
 
         getLogger().info("Handling resource dependencies");
-        if (json.containsKey("scriptDependencies")) {
-            connection.loadScriptDependencies(
-                    json.getJSStringArray("scriptDependencies"));
-        }
-        if (json.containsKey("styleDependencies")) {
-            connection.loadStyleDependencies(
-                    json.getJSStringArray("styleDependencies"));
-        }
+        connection.getDependencyLoader().loadDependencies(json);
 
         handleUIDLDuration.logDuration(
                 " * Handling type mappings from server completed", 10);