com.calclab.emite.browser.PageAssist.java Source code

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Here is the source code for com.calclab.emite.browser.PageAssist.java

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/*
 * ((e)) emite: A pure Google Web Toolkit XMPP library
 * Copyright (c) 2008-2011 The Emite development team
 * 
 * This file is part of Emite.
 *
 * Emite is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Lesser General Public License as
 * published by the Free Software Foundation, either version 3
 * of the License, or (at your option) any later version.
 *
 * Emite is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU Lesser General Public License for more details.
 * 
 * You should have received a copy of the GNU Lesser General Public
 * License along with Emite.  If not, see <http://www.gnu.org/licenses/>.
 */

package com.calclab.emite.browser;

import static com.google.common.base.Preconditions.checkNotNull;

import javax.annotation.Nullable;

import com.google.gwt.dom.client.Document;
import com.google.gwt.dom.client.Element;
import com.google.gwt.dom.client.NodeList;
import com.google.gwt.user.client.DOM;

/**
 * An utility class to perform actions based on meta tags.
 */
public final class PageAssist {

    /**
     * Get the value of meta information written in the html page. The meta
     * information is a html tag with name of meta usually placed inside the the
     * head section with two attributes: id and content. For example:
     * 
     * <code>&lt;meta name="name" value="userName" /&gt;</code>
     * 
     * @param id
     *            the 'id' value of the desired meta tag
     * @param defaultValue
     *            the default value to return if the meta is not found
     * @return the value of the attribute 'value' or null if not found
     */
    @Nullable
    public static final String getMeta(final String id, @Nullable final String defaultValue) {
        checkNotNull(id);
        final NodeList<Element> elements = Document.get().getElementsByTagName("meta");
        for (int i = 0; i < elements.getLength(); i++) {
            final Element candidate = elements.getItem(i);
            if (id.equals(candidate.getAttribute("name")))
                return candidate.getPropertyString("content");
        }

        final Element domElement = DOM.getElementById(id);
        if (domElement != null)
            return domElement.getPropertyString("content");

        return defaultValue;
    }

    /**
     * Return an int value for the meta
     * 
     * @param id
     *            the 'id' value of the desired meta tag
     * @param defaultValue
     *            the default value to return if the meta is not found
     * @return the int value of the meta tag, null if it is invalid or doesn't
     *         exist
     */
    public static final int getMeta(final String id, final int defaultValue) {
        final String metaValue = getMeta(id, null);

        if (metaValue == null)
            return defaultValue;

        try {
            return Integer.parseInt(metaValue);
        } catch (final NumberFormatException e) {
            return defaultValue;
        }
    }

    /**
     * Returns the true/false value of a meta tag.
     * 
     * @param id
     *            the 'id' value of the desired meta tag
     * @param defaultValue
     *            the value to return if the meta value is neither
     *            <code>"true"</code> nor <code>"false"</code>
     * @return true if the given meta is "true", false if the given meta is
     *         "false" otherwise the defaultValue.
     */
    public static final boolean getMeta(final String id, final boolean defaultValue) {
        final String metaValue = getMeta(id, null);

        if (metaValue == null)
            return defaultValue;

        return Boolean.parseBoolean(metaValue);
    }

    private PageAssist() {
    }

}