| /* |
| * Copyright 2011 Google Inc. |
| * |
| * 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.google.gwt.core.client.impl; |
| |
| import com.google.gwt.core.client.JavaScriptObject; |
| import com.google.gwt.core.client.impl.AsyncFragmentLoader.HttpDownloadFailure; |
| |
| /** |
| * A download strategy that uses a JSONP style script tag mechanism. and is |
| * therefore cross site compatible. Note that if this strategy is used, the |
| * deferred fragments must be wrapped in a callback called runAsyncCallbackX() |
| * where X is the fragment number. |
| * |
| * This is the default strategy for the CrossSiteIframeLinker. |
| * |
| * TODO(unnurg): Try to use the ScriptInjector here |
| */ |
| |
| public class ScriptTagLoadingStrategy extends LoadingStrategyBase { |
| |
| /** |
| * Uses a JSONP style script tag mechanism to download the code. |
| */ |
| protected static class ScriptTagDownloadStrategy implements DownloadStrategy { |
| @Override |
| public void tryDownload(final RequestData request) { |
| int fragment = request.getFragment(); |
| JavaScriptObject scriptTag = createScriptTag(request.getUrl()); |
| setOnSuccess(fragment, onSuccess(fragment, scriptTag, request)); |
| setOnFailure(scriptTag, onFailure(fragment, scriptTag, request)); |
| installScriptTag(scriptTag); |
| } |
| } |
| |
| protected static void callOnLoadError(RequestData request) { |
| request.onLoadError(new HttpDownloadFailure(request.getUrl(), 404, |
| "Script Tag Failure - no status available"), true); |
| } |
| |
| private static native boolean clearCallbacksAndRemoveTag( |
| int fragment, JavaScriptObject scriptTag) /*-{ |
| if (scriptTag.parentNode == null) { |
| // onSuccess or onFailure must have already been called. |
| return false; |
| } |
| var head = document.getElementsByTagName('head').item(0); |
| @com.google.gwt.core.client.impl.ScriptTagLoadingStrategy::clearOnSuccess(I)(fragment); |
| @com.google.gwt.core.client.impl.ScriptTagLoadingStrategy::clearOnFailure(Lcom/google/gwt/core/client/JavaScriptObject;)( |
| scriptTag); |
| head.removeChild(scriptTag); |
| return true; |
| }-*/; |
| |
| private static native void clearOnFailure(JavaScriptObject scriptTag) /*-{ |
| scriptTag.onerror = scriptTag.onload = scriptTag.onreadystatechange = function(){}; |
| }-*/; |
| |
| private static native void clearOnSuccess(int fragment) /*-{ |
| delete __gwtModuleFunction['runAsyncCallback' + fragment]; |
| }-*/; |
| |
| private static native JavaScriptObject createScriptTag(String url) /*-{ |
| var head = document.getElementsByTagName('head').item(0); |
| var scriptTag = document.createElement('script'); |
| scriptTag.src = url; |
| return scriptTag; |
| }-*/; |
| |
| private static native void installScriptTag(JavaScriptObject scriptTag) /*-{ |
| var head = document.getElementsByTagName('head').item(0); |
| head.appendChild(scriptTag); |
| }-*/; |
| |
| private static native JavaScriptObject onFailure( |
| int fragment, JavaScriptObject scriptTag, RequestData request) /*-{ |
| return function() { |
| if (@com.google.gwt.core.client.impl.ScriptTagLoadingStrategy::clearCallbacksAndRemoveTag(ILcom/google/gwt/core/client/JavaScriptObject;)( |
| fragment, scriptTag)) { |
| @com.google.gwt.core.client.impl.ScriptTagLoadingStrategy::callOnLoadError(Lcom/google/gwt/core/client/impl/LoadingStrategyBase$RequestData;)( |
| request) |
| } |
| } |
| }-*/; |
| |
| private static native JavaScriptObject onSuccess(int fragment, |
| JavaScriptObject scriptTag, RequestData request) /*-{ |
| return function(code, instance) { |
| if (@com.google.gwt.core.client.impl.ScriptTagLoadingStrategy::clearCallbacksAndRemoveTag(ILcom/google/gwt/core/client/JavaScriptObject;)( |
| fragment, scriptTag)) { |
| request.@com.google.gwt.core.client.impl.LoadingStrategyBase.RequestData::tryInstall(Ljava/lang/String;)( |
| code); |
| } |
| } |
| }-*/; |
| |
| private static native void setOnFailure(JavaScriptObject script, |
| JavaScriptObject callback) /*-{ |
| script.onerror = function() { |
| callback(); |
| } |
| script.onload = function() { |
| callback(); |
| } |
| script.onreadystatechange = function () { |
| if (script.readyState == 'loaded' || script.readyState == 'complete') { |
| script.onreadystatechange = function () { } |
| callback(); |
| } |
| } |
| }-*/; |
| |
| private static native void setOnSuccess(int fragment, JavaScriptObject callback) /*-{ |
| __gwtModuleFunction['runAsyncCallback'+fragment] = callback; |
| }-*/; |
| |
| public ScriptTagLoadingStrategy() { |
| super(new ScriptTagDownloadStrategy()); |
| } |
| } |