Java tutorial
/* * Copyright 2008 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.linker; import com.google.gwt.core.ext.LinkerContext; import com.google.gwt.core.ext.TreeLogger; import com.google.gwt.core.ext.UnableToCompleteException; import com.google.gwt.core.ext.linker.ArtifactSet; import com.google.gwt.core.ext.linker.CompilationResult; import com.google.gwt.core.ext.linker.LinkerOrder; import com.google.gwt.core.ext.linker.LinkerOrder.Order; import com.google.gwt.core.ext.linker.Shardable; import com.google.gwt.core.ext.linker.impl.SelectionScriptLinker; import com.google.gwt.dev.About; import com.google.gwt.dev.util.DefaultTextOutput; import com.google.gwt.dev.util.Util; /** * Implements the canonical GWT bootstrap sequence that loads the GWT module in * a separate iframe. */ @LinkerOrder(Order.PRIMARY) @Shardable public class IFrameLinker extends SelectionScriptLinker { /** * This string is inserted between script chunks. It is made default access * for testing. */ static final String SCRIPT_CHUNK_SEPARATOR = "--></script>\n<script><!--\n"; @Override public String getDescription() { return "Standard"; } /* * This implementation divides the code of the initial fragment into multiple * script tags. These chunked script tags loads faster on Firefox even when * the data is cached. Additionally, having the script tags separated means * that the early ones can be evaluated before the later ones have finished * downloading. As a result of this parallelism, the overall time to get the * JavaScript downloaded and evaluated can lower. */ @Override protected byte[] generatePrimaryFragment(TreeLogger logger, LinkerContext context, CompilationResult result, String[] js, ArtifactSet artifacts) throws UnableToCompleteException { StringBuffer b = new StringBuffer(); b.append(getModulePrefix(logger, context, result.getStrongName(), js.length)); b.append(splitPrimaryJavaScript(result.getStatementRanges()[0], js[0], charsPerChunk(context, logger), getScriptChunkSeparator(logger, context))); b.append(getModuleSuffix(logger, context)); return Util.getBytes(b.toString()); } @Override protected String getCompilationExtension(TreeLogger logger, LinkerContext context) { return ".cache.html"; } @Override protected String getHostedFilename() { return "hosted.html"; } @Override protected String getModulePrefix(TreeLogger logger, LinkerContext context, String strongName) throws UnableToCompleteException { return getModulePrefix(logger, context, strongName, true); } @Override protected String getModulePrefix(TreeLogger logger, LinkerContext context, String strongName, int numFragments) throws UnableToCompleteException { return getModulePrefix(logger, context, strongName, numFragments > 1); } @Override protected String getModuleSuffix(TreeLogger logger, LinkerContext context) { DefaultTextOutput out = new DefaultTextOutput(context.isOutputCompact()); out.print("$stats && $stats({moduleName:'" + context.getModuleName() + "',sessionId:$sessionId" + ",subSystem:'startup',evtGroup:'moduleStartup'" + ",millis:(new Date()).getTime(),type:'moduleEvalEnd'});"); // Generate the call to tell the bootstrap code that we're ready to go. out.newlineOpt(); out.print("if ($wnd." + context.getModuleFunctionName() + ") $wnd." + context.getModuleFunctionName() + ".onScriptLoad();"); out.newline(); out.print("--></script></body></html>"); out.newlineOpt(); return out.toString(); } @Override protected String getScriptChunkSeparator(TreeLogger logger, LinkerContext context) { return SCRIPT_CHUNK_SEPARATOR; } @Override protected String getSelectionScriptTemplate(TreeLogger logger, LinkerContext context) { return "com/google/gwt/core/linker/IFrameTemplate.js"; } protected String modifyPrimaryJavaScript(String js) { return js; } /** * This is the real implementation of <code>getModulePrefix</code> for this * linker. The other versions forward to this one. */ private String getModulePrefix(TreeLogger logger, LinkerContext context, String strongName, boolean supportRunAsync) throws UnableToCompleteException { DefaultTextOutput out = new DefaultTextOutput(context.isOutputCompact()); out.print("<html>"); out.newlineOpt(); // Setup the well-known variables. out.print("<head><meta charset=\"UTF-8\" /><script>"); out.newlineOpt(); out.print("var $gwt_version = \"" + About.getGwtVersionNum() + "\";"); out.newlineOpt(); out.print("var $wnd = parent;"); out.newlineOpt(); out.print("var $doc = $wnd.document;"); out.newlineOpt(); out.print("var $moduleName, $moduleBase;"); out.newlineOpt(); out.print("var $strongName = '" + strongName + "';"); out.newlineOpt(); if (supportRunAsync) { out.print("function __gwtStartLoadingFragment(frag) {"); out.indentIn(); out.newlineOpt(); out.print(" return $moduleBase + '" + getFragmentSubdir(logger, context) + "/' + $strongName + '/' + frag + '" + FRAGMENT_EXTENSION + "';"); out.indentOut(); out.newlineOpt(); out.print("};"); out.newlineOpt(); out.print("function __gwtInstallCode(code) {"); /* * Use a script tag on all platforms, for simplicity. It would be cleaner * to use window.eval, but at the time of writing that only reliably works * on Firefox. It would also be cleaner to use window.execScript on * platforms that support it (IE and Chrome). However, trying this causes * IE 6 (and possibly others) to emit "error 80020101", apparently due to * something objectionable in the compiler's output JavaScript. */ out.indentIn(); out.newlineOpt(); out.print("var head = document.getElementsByTagName('head').item(0);"); out.newlineOpt(); out.print("var script = document.createElement('script');"); out.newlineOpt(); out.print("script.type = 'text/javascript';"); out.newlineOpt(); out.print("script.text = code;"); out.newlineOpt(); out.print("head.appendChild(script);"); out.indentOut(); out.newlineOpt(); out.print("};"); out.newlineOpt(); } out.print("var $stats = $wnd.__gwtStatsEvent ? function(a) {return $wnd.__gwtStatsEvent(a);} : null,"); out.newlineOpt(); out.print("$sessionId = $wnd.__gwtStatsSessionId ? $wnd.__gwtStatsSessionId : null;"); out.newlineOpt(); out.print("$stats && $stats({moduleName:'" + context.getModuleName() + "',sessionId:$sessionId" + ",subSystem:'startup',evtGroup:'moduleStartup'" + ",millis:(new Date()).getTime(),type:'moduleEvalStart'});"); out.newlineOpt(); out.print("</script></head>"); out.newlineOpt(); out.print("<body>"); out.newlineOpt(); // Begin a script block inside the body. It's commented out so that the // browser won't mistake strings containing "<script>" for actual script. out.print("<script><!--"); out.newline(); return out.toString(); } }