com.google.gwt.core.ext.linker.impl.ResourceInjectionUtil.java Source code

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Here is the source code for com.google.gwt.core.ext.linker.impl.ResourceInjectionUtil.java

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/*
 * Copyright 2010 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.ext.linker.impl;

import com.google.gwt.core.ext.linker.ArtifactSet;
import com.google.gwt.core.ext.linker.ScriptReference;
import com.google.gwt.core.ext.linker.StylesheetReference;

import java.net.MalformedURLException;
import java.net.URL;

/**
 * Utility class to help linkers do resource injection.
 */
public class ResourceInjectionUtil {
    /**
     * Installs stylesheets and scripts.
     */
    public static StringBuffer injectResources(StringBuffer selectionScript, ArtifactSet artifacts) {
        // Add external dependencies
        int startPos = selectionScript.indexOf("// __MODULE_STYLES_END__");
        if (startPos != -1) {
            for (StylesheetReference resource : artifacts.find(StylesheetReference.class)) {
                String text = generateStylesheetInjector(resource.getSrc());
                selectionScript.insert(startPos, text);
                startPos += text.length();
            }
        }

        startPos = selectionScript.indexOf("// __MODULE_SCRIPTS_END__");
        if (startPos != -1) {
            for (ScriptReference resource : artifacts.find(ScriptReference.class)) {
                String text = generateScriptInjector(resource.getSrc());
                selectionScript.insert(startPos, text);
                startPos += text.length();
            }
        }
        return selectionScript;
    }

    /**
     * Installs stylesheets using the installOneStylesheet method, which is
     * assumed to be defined on the page.  The installOneStylesheet() 
     * helper function is invoked as follows:
     * 
     * <pre>
     * installOneStylesheet(URL);
     * </pre>
     */
    public static StringBuffer injectStylesheets(StringBuffer selectionScript, ArtifactSet artifacts) {
        int startPos = selectionScript.indexOf("// __MODULE_STYLES__");
        if (startPos != -1) {
            for (StylesheetReference resource : artifacts.find(StylesheetReference.class)) {
                String text = "installOneStylesheet('" + resource.getSrc() + "');\n";
                selectionScript.insert(startPos, text);
                startPos += text.length();
            }
        }
        return selectionScript;
    }

    private static String generateScriptInjector(String scriptUrl) {
        if (isRelativeURL(scriptUrl)) {
            return "  if (!__gwt_scriptsLoaded['" + scriptUrl + "']) {\n" + "    __gwt_scriptsLoaded['" + scriptUrl
                    + "'] = true;\n" + "    document.write('<script language=\\\"javascript\\\" src=\\\"'+base+'"
                    + scriptUrl + "\\\"></script>');\n" + "  }\n";
        } else {
            return "  if (!__gwt_scriptsLoaded['" + scriptUrl + "']) {\n" + "    __gwt_scriptsLoaded['" + scriptUrl
                    + "'] = true;\n" + "    document.write('<script language=\\\"javascript\\\" src=\\\""
                    + scriptUrl + "\\\"></script>');\n" + "  }\n";
        }
    }

    /**
     * Generate a Snippet of JavaScript to inject an external stylesheet.
     * 
     * <pre>
     * if (!__gwt_stylesLoaded['URL']) {
     *   var l = $doc.createElement('link');
     *   __gwt_styleLoaded['URL'] = l;
     *   l.setAttribute('rel', 'stylesheet');
     *   l.setAttribute('href', HREF_EXPR);
     *   $doc.getElementsByTagName('head')[0].appendChild(l);
     * }
     * </pre>
     */
    private static String generateStylesheetInjector(String stylesheetUrl) {
        String hrefExpr = "'" + stylesheetUrl + "'";
        if (isRelativeURL(stylesheetUrl)) {
            hrefExpr = "base + " + hrefExpr;
        }

        return "if (!__gwt_stylesLoaded['" + stylesheetUrl + "']) {\n           "
                + "  var l = $doc.createElement('link');\n                          " + "  __gwt_stylesLoaded['"
                + stylesheetUrl + "'] = l;\n             "
                + "  l.setAttribute('rel', 'stylesheet');\n                         " + "  l.setAttribute('href', "
                + hrefExpr + ");\n                    "
                + "  $doc.getElementsByTagName('head')[0].appendChild(l);\n         " + "}\n";
    }

    /**
     * Determines whether or not the URL is relative.
     * 
     * @param src the test url
     * @return <code>true</code> if the URL is relative, <code>false</code> if not
     */
    private static boolean isRelativeURL(String src) {
        // A straight absolute url for the same domain, server, and protocol.
        if (src.startsWith("/")) {
            return false;
        }

        // If it can be parsed as a URL, then it's probably absolute.
        try {
            // Just check to see if it can be parsed, no need to store the result.
            new URL(src);

            // Let's guess that it is absolute (thus, not relative).
            return false;
        } catch (MalformedURLException e) {
            // Do nothing, since it was a speculative parse.
        }

        // Since none of the above matched, let's guess that it's relative.
        return true;
    }

}