Java URL Connection getLastModified(URLConnection connection)

Description

get Last Modified

License

Apache License

Declaration

public static long getLastModified(URLConnection connection) throws IOException 

Method Source Code

//package com.java2s;
/*/*from  w w  w.  j  a v  a2s.c o  m*/
 *  Licensed to the Apache Software Foundation (ASF) under one
 *  or more contributor license agreements.  See the NOTICE file
 *  distributed with this work for additional information
 *  regarding copyright ownership.  The ASF licenses this file
 *  to you 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.
 */

import java.io.File;
import java.io.IOException;
import java.net.JarURLConnection;
import java.net.URL;
import java.net.URLConnection;

public class Main {
    public static long getLastModified(URL url) throws IOException {
        if ("file".equals(url.getProtocol())) {
            String externalForm = url.toExternalForm();
            // Remove the "file:"
            File file = new File(externalForm.substring(5));

            return file.lastModified();
        } else {
            return getLastModified(url.openConnection());
        }
    }

    public static long getLastModified(URLConnection connection) throws IOException {
        long modified;
        if (connection instanceof JarURLConnection) {
            // The following hack is required to work-around a JDK bug.
            // getLastModified() on a JAR entry URL delegates to the actual JAR file
            // rather than the JAR entry.
            // This opens internally, and does not close, an input stream to the JAR
            // file.
            // In turn, you cannot close it by yourself, because it's internal.
            // The work-around is to get the modification date of the JAR file
            // manually,
            // and then close that connection again.

            URL jarFileUrl = ((JarURLConnection) connection).getJarFileURL();
            URLConnection jarFileConnection = jarFileUrl.openConnection();

            try {
                modified = jarFileConnection.getLastModified();
            } finally {
                try {
                    jarFileConnection.getInputStream().close();
                } catch (Exception exception) {
                    // Ignored
                }
            }
        } else {
            modified = connection.getLastModified();
        }

        return modified;
    }
}

Related

1. getHttpResponseHeader(URLConnection http)
2. getImageFromURL(String remoteURL)
3. getJar(String jarUrl)
4. getJarUrlForPackage(String packageName)
5. getLastModified(URL url)
6. getLength(String htmlUrl)
7. getLines(final URL url, final int linesToRead)
8. getOutputStream(final URL outputURL)
9. getOutputStream(URL url)