Urls.java Source code

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Here is the source code for Urls.java

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/*
GNU LESSER GENERAL PUBLIC LICENSE
Copyright (C) 2006 The Lobo Project
    
This library 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 2.1 of the License, or (at your option) any later version.
    
This library 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 this library; if not, write to the Free Software
Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
    
Contact info: lobochief@users.sourceforge.net
*/
/*
 * Created on Jun 12, 2005
 */

import java.net.*;
import java.text.DateFormat;
import java.text.SimpleDateFormat;
import java.util.*;
import java.util.logging.*;

public class Urls {
    private static final Logger logger = Logger.getLogger(Urls.class.getName());
    public static final DateFormat PATTERN_RFC1123 = new SimpleDateFormat("EEE, dd MMM yyyy HH:mm:ss zzz",
            Locale.US);

    static {
        DateFormat df = PATTERN_RFC1123;
        df.setTimeZone(TimeZone.getTimeZone("GMT"));
    }

    private Urls() {
        super();
    }

    /** Whether the URL refers to a resource in the local file system. */
    public static boolean isLocal(java.net.URL url) {
        if (isLocalFile(url)) {
            return true;
        }
        String protocol = url.getProtocol();
        if ("jar".equalsIgnoreCase(protocol)) {
            String path = url.getPath();
            int emIdx = path.lastIndexOf('!');
            String subUrlString = emIdx == -1 ? path : path.substring(0, emIdx);
            try {
                URL subUrl = new URL(subUrlString);
                return isLocal(subUrl);
            } catch (java.net.MalformedURLException mfu) {
                return false;
            }
        } else {
            return false;
        }
    }

    /** Whether the URL is a file in the local file system. */
    public static boolean isLocalFile(java.net.URL url) {
        String scheme = url.getProtocol();
        return "file".equalsIgnoreCase(scheme) && !hasHost(url);
    }

    public static boolean hasHost(java.net.URL url) {
        String host = url.getHost();
        return host != null && !"".equals(host);
    }

    /**
     * Creates an absolute URL in a manner equivalent to
     * major browsers. 
     */
    public static URL createURL(URL baseUrl, String relativeUrl) throws java.net.MalformedURLException {
        return new URL(baseUrl, relativeUrl);
    }

    /**
     * Returns the time when the document should be considered expired.
     * The time will be zero if the document always needs to be revalidated.
     * It will be <code>null</code> if no expiration time is specified.
     */
    public static Long getExpiration(URLConnection connection, long baseTime) {
        String cacheControl = connection.getHeaderField("Cache-Control");
        if (cacheControl != null) {
            StringTokenizer tok = new StringTokenizer(cacheControl, ",");
            while (tok.hasMoreTokens()) {
                String token = tok.nextToken().trim().toLowerCase();
                if ("must-revalidate".equals(token)) {
                    return new Long(0);
                } else if (token.startsWith("max-age")) {
                    int eqIdx = token.indexOf('=');
                    if (eqIdx != -1) {
                        String value = token.substring(eqIdx + 1).trim();
                        int seconds;
                        try {
                            seconds = Integer.parseInt(value);
                            return new Long(baseTime + seconds * 1000);
                        } catch (NumberFormatException nfe) {
                            logger.warning("getExpiration(): Bad Cache-Control max-age value: " + value);
                            // ignore
                        }
                    }
                }
            }
        }
        String expires = connection.getHeaderField("Expires");
        if (expires != null) {
            try {
                synchronized (PATTERN_RFC1123) {
                    Date expDate = PATTERN_RFC1123.parse(expires);
                    return new Long(expDate.getTime());
                }
            } catch (java.text.ParseException pe) {
                int seconds;
                try {
                    seconds = Integer.parseInt(expires);
                    return new Long(baseTime + seconds * 1000);
                } catch (NumberFormatException nfe) {
                    logger.warning("getExpiration(): Bad Expires header value: " + expires);
                }
            }
        }
        return null;
    }

    private static String getDefaultCharset(URLConnection connection) {
        URL url = connection.getURL();
        if (Urls.isLocalFile(url)) {
            String charset = System.getProperty("file.encoding");
            return charset == null ? "ISO-8859-1" : charset;
        } else {
            return "ISO-8859-1";
        }
    }

    public static String getNoRefForm(URL url) {
        String host = url.getHost();
        int port = url.getPort();
        String portText = port == -1 ? "" : ":" + port;
        String userInfo = url.getUserInfo();
        String userInfoText = userInfo == null || userInfo.length() == 0 ? "" : userInfo + "@";
        String hostPort = host == null || host.length() == 0 ? "" : "//" + userInfoText + host + portText;
        return url.getProtocol() + ":" + hostPort + url.getFile();
    }

}