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- /*
- * Copyright 2000-2021 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.JsArray;
- 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
- */
- public class DependencyLoader {
-
- private static final String DEPENDENCIES = "dependencies";
- private ApplicationConnection connection = null;
-
- private ResourceLoader loader = ResourceLoader.get();
-
- private ResourceLoadListener dependencyLoadingTracker = new ResourceLoadListener() {
-
- @Override
- public void onLoad(ResourceLoadEvent event) {
- ApplicationConfiguration.endDependencyLoading();
- }
-
- @Override
- public void onError(ResourceLoadEvent event) {
- String error = event.getResourceUrl() + " could not be loaded.";
- if (event.getResourceUrl().endsWith("css")) {
- error += " or the load detection failed because the stylesheet is empty.";
- }
- getLogger().severe(error);
- // The show must go on
- onLoad(event);
- }
- };
-
- /**
- * 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.
- *
- * Handles all dependencies found with the key "{@literal dependencies}".
- *
- * Ensures that
- * <ul>
- * <li>JavaScript dependencies are loaded in the given order.
- * <li>HTML imports are loaded after all JavaScripts are loaded and
- * executed.
- * <li>Style sheets are loaded and evaluated in some undefined order
- * </ul>
- *
- * @param json
- * the JSON containing the dependencies to load
- */
- public void loadDependencies(ValueMap json) {
- if (!json.containsKey(DEPENDENCIES)) {
- return;
- }
- JsArray<ValueMap> deps = json.getJSValueMapArray(DEPENDENCIES);
-
- for (int i = 0; i < deps.length(); i++) {
- ValueMap dep = deps.get(i);
- String type = dep.getAsString("type");
- String url = connection.translateVaadinUri(dep.getAsString("url"));
- ApplicationConfiguration.startDependencyLoading();
- if (type.equals("STYLESHEET")) {
- loader.loadStylesheet(url, dependencyLoadingTracker);
- } else if (type.equals("JAVASCRIPT")) {
- loader.loadScript(url, dependencyLoadingTracker);
- } else if (type.equals("HTMLIMPORT")) {
- loader.loadHtmlImport(url, dependencyLoadingTracker);
- } else {
- ApplicationConfiguration.endDependencyLoading();
- throw new IllegalArgumentException("Unknown type: " + type);
- }
- }
- }
-
- private static Logger getLogger() {
- return Logger.getLogger(DependencyLoader.class.getName());
- }
-
- }
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