Java tutorial
/* * 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.user.rebind; import com.google.gwt.core.ext.TreeLogger; import com.google.gwt.core.ext.linker.ConfigurationProperty; import com.google.gwt.core.ext.linker.PropertyProviderGenerator; import java.util.Arrays; import java.util.List; import java.util.SortedSet; /** * Generator which writes out the JavaScript for determining the value of the * <code>user.agent</code> selection property. */ public class UserAgentPropertyGenerator implements PropertyProviderGenerator { /** * List of valid user agent selection property values, which helps ensure that * UserAgent.gwt.xml stays in sync with the * {@link #writeUserAgentPropertyJavaScript(SourceWriter)} method body of this * class. */ private static final List<String> VALID_VALUES = Arrays .asList(new String[] { "ie6", "ie8", "gecko1_8", "safari", "opera", "ie9" }); /** * List of predicates to identify user agent. * The order of evaluation is from top to bottom, i.e., the first matching * predicate will have the associated ua token returned. * ua is defined in an outer scope and is therefore visible in * the predicate javascript fragment. */ private static UserAgentPropertyGeneratorPredicate[] predicates = new UserAgentPropertyGeneratorPredicate[] { // opera new UserAgentPropertyGeneratorPredicate("opera").getPredicateBlock() .println("return (ua.indexOf('opera') != -1);").returns("'opera'"), // webkit family (chrome, safari and chromeframe). new UserAgentPropertyGeneratorPredicate("safari").getPredicateBlock().println("return (") .println("(ua.indexOf('webkit') != -1)").println("||").println("(function() {") .println("if (ua.indexOf('chromeframe') != -1) {").println("return true;").println("}") .println("if (typeof window['ActiveXObject'] != 'undefined') {").println("try {") .println("var obj = new ActiveXObject('ChromeTab.ChromeFrame');").println("if (obj) {") .println("obj.registerBhoIfNeeded();").println("return true;").println("}") .println("} catch(e) { }").println("}").println("return false;").println("})()").println(")") .returns("'safari'"), // IE9 new UserAgentPropertyGeneratorPredicate("ie9").getPredicateBlock() .println("return (ua.indexOf('msie') != -1 && ($doc.documentMode >= 9));").returns("'ie9'"), // IE8 new UserAgentPropertyGeneratorPredicate("ie8").getPredicateBlock() .println("return (ua.indexOf('msie') != -1 && ($doc.documentMode >= 8));").returns("'ie8'"), // IE6 new UserAgentPropertyGeneratorPredicate("ie6").getPredicateBlock() .println("var result = /msie ([0-9]+)\\.([0-9]+)/.exec(ua);") .println("if (result && result.length == 3)").indent() .println("return (makeVersion(result) >= 6000);").outdent().returns("'ie6'"), // gecko family new UserAgentPropertyGeneratorPredicate("gecko1_8").getPredicateBlock() .println("return (ua.indexOf('gecko') != -1);").returns("'gecko1_8'"), }; /** * Writes out the JavaScript function body for determining the value of the * <code>user.agent</code> selection property. This method is used to create * the selection script and by {@link UserAgentGenerator} to assert at runtime * that the correct user agent permutation is executing. The list of * <code>user.agent</code> values listed here should be kept in sync with * {@link #VALID_VALUES} and <code>UserAgent.gwt.xml</code>. */ static void writeUserAgentPropertyJavaScript(SourceWriter body, SortedSet<String> possibleValues) { // write preamble body.println("var ua = navigator.userAgent.toLowerCase();"); body.println("var makeVersion = function(result) {"); body.indent(); body.println("return (parseInt(result[1]) * 1000) + parseInt(result[2]);"); body.outdent(); body.println("};"); // write only selected user agents for (int i = 0; i < predicates.length; i++) { if (possibleValues.contains(predicates[i].getUserAgent())) { body.println("if ((function() { "); body.indent(); body.print(predicates[i].toString()); body.outdent(); body.println("})()) return " + predicates[i].getReturnValue() + ";"); } } // default return body.println("return 'unknown';"); } public String generate(TreeLogger logger, SortedSet<String> possibleValues, String fallback, SortedSet<ConfigurationProperty> configProperties) { for (String value : possibleValues) { if (!VALID_VALUES.contains(value)) { logger.log(TreeLogger.WARN, "Unrecognized " + UserAgentGenerator.PROPERTY_USER_AGENT + " property value '" + value + "', possibly due to UserAgent.gwt.xml and " + UserAgentPropertyGenerator.class.getName() + " being out of sync." + " Use <set-configuration-property name=\"" + UserAgentGenerator.PROPERTY_USER_AGENT_RUNTIME_WARNING + "\" value=\"false\"/> to suppress this warning message."); } } // make sure that the # of ua in VALID_VALUES // is the same of predicates. maybe should iterate // to make sure each one has a match. assert predicates.length == VALID_VALUES.size(); StringSourceWriter body = new StringSourceWriter(); body.println("{"); body.indent(); writeUserAgentPropertyJavaScript(body, possibleValues); body.outdent(); body.println("}"); return body.toString(); } }