Get URLConnection Expiration
/*
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();
}
}
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