Java HTTP Response getResourceLastModified(URLConnection connection)

Description

get Resource Last Modified

License

Apache License

Declaration

public static long getResourceLastModified(URLConnection connection) throws IOException 

Method Source Code

//package com.java2s;
/*//from ww w.  ja v  a2 s  .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 getResourceLastModified(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 getResourceLastModified(url.openConnection());
        }
    }

    public static long getResourceLastModified(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. getResourceModifiedTime(URL url)
2. getResponse(HttpURLConnection httpConn, StringBuilder responseContent, StringBuilder responseCode, HashMap headers)
3. getResponse(URL request)
4. getResponse(URL url)