001/*
002 *  Copyright 2012 GWT-Bootstrap
003 *
004 *  Licensed under the Apache License, Version 2.0 (the "License");
005 *  you may not use this file except in compliance with the License.
006 *  You may obtain a copy of the License at
007 *
008 *      http://www.apache.org/licenses/LICENSE-2.0
009 *
010 *  Unless required by applicable law or agreed to in writing, software
011 *  distributed under the License is distributed on an "AS IS" BASIS,
012 *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
013 *  See the License for the specific language governing permissions and
014 *  limitations under the License.
015 */
016package com.github.gwtbootstrap.client.ui.resources;
017
018import com.google.gwt.dom.client.Document;
019import com.google.gwt.dom.client.Element;
020import com.google.gwt.dom.client.HeadElement;
021
022/**
023 * Base class for classes that inject someting into the document header.
024 * 
025 * @since 2.0.4.0
026 * @author Carlos Alexandro Becker
027 * @author Dominik Mayer
028 */
029public abstract class AbstractInjector {
030
031        private static HeadElement head;
032
033        /**
034         * Gets the document header.
035         * 
036         * @return the document header
037         */
038        protected static HeadElement getHead() {
039                if (head == null) {
040                        Element element =
041                                        Document.get().getElementsByTagName("head").getItem(0);
042                        assert element != null : "HTML Head element required";
043                        HeadElement head = HeadElement.as(element);
044                        AbstractInjector.head = head;
045                }
046                return AbstractInjector.head;
047        }
048}