java.net.HttpURLConnection#getLastModified ( )源码实例Demo

@Override
public CacheEntry call() throws Exception {
    LOGGER.log(Level.FINE, "Attempting to fetch remote avatar: {0}", url);
    long start = System.nanoTime();
    try {
        HttpURLConnection connection = (HttpURLConnection) new URL(url).openConnection();
        try {
            connection.setConnectTimeout(10000);
            connection.setReadTimeout(30000);
            if (!connection.getContentType().startsWith("image/")) {
                return new CacheEntry(url);
            }
            int length = connection.getContentLength();
            // buffered stream should be no more than 16k if we know the length
            // if we don't know the length then 8k is what we will use
            length = length > 0 ? Math.min(16384, length) : 8192;
            try (InputStream is = connection.getInputStream();
                BufferedInputStream bis = new BufferedInputStream(is, length)) {
                BufferedImage image = ImageIO.read(bis);
                if (image == null) {
                    return new CacheEntry(url);
                }
                return new CacheEntry(url, image, connection.getLastModified());
            }
        } finally {
            connection.disconnect();
        }
    } catch (IOException e) {
        LOGGER.log(Level.INFO, e.getMessage(), e);
        return new CacheEntry(url);
    } finally {
        long end = System.nanoTime();
        long duration = TimeUnit.NANOSECONDS.toMillis(end - start);
        LOGGER.log(duration > 250 ? Level.INFO : Level.FINE, "Avatar lookup of {0} took {1}ms",
            new Object[]{url, duration}
        );
    }
}
 

/**
 * isValid
 * 
 * @return boolean
 */
public boolean isValid() {
	if (timestamp == -1) {
		return false;
	}
	if (expires >= System.currentTimeMillis()) {
		return true;
	}
	try {
		URLConnection connection = getURI().toURL().openConnection();
		if (connection instanceof HttpURLConnection) {
			connection.setIfModifiedSince(timestamp);
			((HttpURLConnection) connection).setRequestMethod("HEAD"); //$NON-NLS-1$
		}
		connection.connect();
		if (connection instanceof HttpURLConnection) {
			HttpURLConnection httpConnection = (HttpURLConnection) connection;
			long lastModified = httpConnection.getLastModified();
			if (httpConnection.getResponseCode() == HttpURLConnection.HTTP_NOT_MODIFIED || (lastModified != 0 && timestamp >= lastModified)) {
				expires = System.currentTimeMillis();
				long expiration = connection.getExpiration();
				long date = connection.getDate();
				if (expiration != 0 && date != 0 && expiration > date) {
					expires += (expiration - date);
				} else {
					expires += 10 * 1000; // 10 sec
				}
				return true;
			}
		}
	} catch (IOException e) {
		IdeLog.logError(CorePlugin.getDefault(), e);
	}
	return false;
}
 

void updatePropertiesFromResponse(HttpURLConnection request) {
    // ETag
    this.getProperties().setEtag(request.getHeaderField(Constants.HeaderConstants.ETAG));

    // Last Modified
    if (0 != request.getLastModified()) {
        final Calendar lastModifiedCalendar = Calendar.getInstance(Utility.LOCALE_US);
        lastModifiedCalendar.setTimeZone(Utility.UTC_ZONE);
        lastModifiedCalendar.setTime(new Date(request.getLastModified()));
        this.getProperties().setLastModified(lastModifiedCalendar.getTime());
    }
}
 

protected void updateEtagAndLastModifiedFromResponse(HttpURLConnection request) {
    // ETag
    this.getProperties().setEtag(request.getHeaderField(Constants.HeaderConstants.ETAG));

    // Last Modified
    if (0 != request.getLastModified()) {
        final Calendar lastModifiedCalendar = Calendar.getInstance(Utility.LOCALE_US);
        lastModifiedCalendar.setTimeZone(Utility.UTC_ZONE);
        lastModifiedCalendar.setTime(new Date(request.getLastModified()));
        this.getProperties().setLastModified(lastModifiedCalendar.getTime());
    }
}
 

private void updatePropertiesFromResponse(HttpURLConnection request) {
    // ETag
    this.getProperties().setEtag(request.getHeaderField(Constants.HeaderConstants.ETAG));

    // Last Modified
    if (0 != request.getLastModified()) {
        final Calendar lastModifiedCalendar = Calendar.getInstance(Utility.LOCALE_US);
        lastModifiedCalendar.setTimeZone(Utility.UTC_ZONE);
        lastModifiedCalendar.setTime(new Date(request.getLastModified()));
        this.getProperties().setLastModified(lastModifiedCalendar.getTime());
    }
}
 

private void updatePropertiesFromResponse(HttpURLConnection request) {
    // ETag
    this.getProperties().setEtag(request.getHeaderField(Constants.HeaderConstants.ETAG));

    // Last Modified
    if (0 != request.getLastModified()) {
        final Calendar lastModifiedCalendar = Calendar.getInstance(Utility.LOCALE_US);
        lastModifiedCalendar.setTimeZone(Utility.UTC_ZONE);
        lastModifiedCalendar.setTime(new Date(request.getLastModified()));
        this.getProperties().setLastModified(lastModifiedCalendar.getTime());
    }
}
 

protected void updateEtagAndLastModifiedFromResponse(HttpURLConnection request) {
    // ETag
    this.getProperties().setEtag(request.getHeaderField(Constants.HeaderConstants.ETAG));

    // Last Modified
    if (0 != request.getLastModified()) {
        final Calendar lastModifiedCalendar = Calendar.getInstance(Utility.LOCALE_US);
        lastModifiedCalendar.setTimeZone(Utility.UTC_ZONE);
        lastModifiedCalendar.setTime(new Date(request.getLastModified()));
        this.getProperties().setLastModified(lastModifiedCalendar.getTime());
    }
}
 

/**
 * Check if there is a new version of the script engine
 * 
 * @throws IOException
 *             if any error occur
 */
private void download() throws IOException {
    boolean is32 = "32".equals( System.getProperty( "sun.arch.data.model" ) );
    String fileName;
    final String os = System.getProperty( "os.name", "" ).toLowerCase();
    if( os.contains( "windows" ) ) {
        fileName = is32 ? "win32" : "win64";
    } else if( os.contains( "mac" ) ) {
        fileName = is32 ? "mac" : "mac64";
    } else if( os.contains( "linux" ) ) {
        fileName = is32 ? "linux-i686" : "linux-x86_64";
    } else {
        throw new IllegalStateException( "Unknown OS: " + os );
    }
    File target = new File( System.getProperty( "java.io.tmpdir" ) + "/SpiderMonkey" );
    URL url = new URL( "https://archive.mozilla.org/pub/firefox/nightly/latest-mozilla-central/jsshell-" + fileName + ".zip" );
    System.out.println( "\tDownload: " + url );
    command = target.getAbsolutePath() + "/js";
    HttpURLConnection conn = (HttpURLConnection)url.openConnection();
    conn.setConnectTimeout( 5000 );
    if( target.exists() ) {
        conn.setIfModifiedSince( target.lastModified() );
    }
    InputStream input;
    try {
        input = conn.getInputStream();
    } catch( IOException ex ) {
        if( target.exists() ) {
            System.err.println( ex );
            return;
        }
        throw ex;
    }
    if( conn.getResponseCode() == HttpURLConnection.HTTP_NOT_MODIFIED ) {
        System.out.println( "\tUP-TP-DATE, use version from " + Instant.ofEpochMilli( target.lastModified() ) );
        return;
    }
    long lastModfied = conn.getLastModified();
    extractStream( input, false, target );
    target.setLastModified( lastModfied );
    System.out.println( "\tUse Version from " + Instant.ofEpochMilli( lastModfied ) );
}
 

private URLConnection openConnection(URL aSource) throws IOException {

            // set up the URL connection
            URLConnection connection = aSource.openConnection();
            // modify the headers
            // NB: things like user authentication could go in here too.
            if (hasTimestamp) {
                connection.setIfModifiedSince(timestamp);
            }

            // in case the plugin manager is its own project, this can become an authenticator
            boolean isSecureProcotol = "https".equalsIgnoreCase(aSource.getProtocol());
            boolean isAuthInfoSet = !Strings.isNullOrEmpty(aSource.getUserInfo());
            if (isAuthInfoSet) {
                if (!isSecureProcotol) {
                    throw new IOException("Basic auth is only supported for HTTPS!");
                }
                String basicAuth = Base64.encodeBytes(aSource.getUserInfo().getBytes(StandardCharsets.UTF_8));
                connection.setRequestProperty("Authorization", "Basic " + basicAuth);
            }

            if (connection instanceof HttpURLConnection) {
                ((HttpURLConnection) connection).setInstanceFollowRedirects(false);
                connection.setUseCaches(true);
                connection.setConnectTimeout(5000);
            }
            connection.setRequestProperty("ES-Version", Version.CURRENT.toString());
            connection.setRequestProperty("ES-Build-Hash", Build.CURRENT.hashShort());
            connection.setRequestProperty("User-Agent", "elasticsearch-plugin-manager");

            // connect to the remote site (may take some time)
            connection.connect();

            // First check on a 301 / 302 (moved) response (HTTP only)
            if (connection instanceof HttpURLConnection) {
                HttpURLConnection httpConnection = (HttpURLConnection) connection;
                int responseCode = httpConnection.getResponseCode();
                if (responseCode == HttpURLConnection.HTTP_MOVED_PERM ||
                        responseCode == HttpURLConnection.HTTP_MOVED_TEMP ||
                        responseCode == HttpURLConnection.HTTP_SEE_OTHER) {
                    String newLocation = httpConnection.getHeaderField("Location");
                    URL newURL = new URL(newLocation);
                    if (!redirectionAllowed(aSource, newURL)) {
                        return null;
                    }
                    return openConnection(newURL);
                }
                // next test for a 304 result (HTTP only)
                long lastModified = httpConnection.getLastModified();
                if (responseCode == HttpURLConnection.HTTP_NOT_MODIFIED
                        || (lastModified != 0 && hasTimestamp && timestamp >= lastModified)) {
                    // not modified so no file download. just return
                    // instead and trace out something so the user
                    // doesn't think that the download happened when it
                    // didn't
                    return null;
                }
                // test for 401 result (HTTP only)
                if (responseCode == HttpURLConnection.HTTP_UNAUTHORIZED) {
                    String message = "HTTP Authorization failure";
                    throw new IOException(message);
                }
            }

            //REVISIT: at this point even non HTTP connections may
            //support the if-modified-since behaviour -we just check
            //the date of the content and skip the write if it is not
            //newer. Some protocols (FTP) don't include dates, of
            //course.
            return connection;
        }
 

@Override
protected Long getLastModifiedForScheme(URI uri) {
	getLogger()
			.warn(MessageFormat
					.format("The URI [{0}] seems to represent an absolute HTTP or HTTPS URL. "
							+ "Getting the last modification timestamp is only possible "
							+ "if the URL is accessible "
							+ "and if the server returns the [Last-Modified] header correctly. "
							+ "This method is not reliable and is likely to fail. "
							+ "In this case the last modification timestamp will be assumed to be unknown.",
							uri));
	try {
		final URL url = uri.toURL();
		try {
			final URLConnection urlConnection = url.openConnection();
			if (urlConnection instanceof HttpURLConnection) {
				final HttpURLConnection httpURLConnection = (HttpURLConnection) urlConnection;
				httpURLConnection.setInstanceFollowRedirects(true);
				final long lastModified = httpURLConnection
						.getLastModified();
				if (lastModified == 0) {
					getLogger()
							.error(MessageFormat
									.format("Could not retrieve the last modification timestamp for the URI [{0}] from the HTTP URL connection. "
											+ "The [Last-Modified] header was probably not set correctly.",
											uri));

				} else {
					getLogger()
							.debug(MessageFormat
									.format("HTTP connection to the URI [{0}] returned the last modification timestamp [{1,date,yyyy-MM-dd HH:mm:ss.SSS}].",
											uri, lastModified));
					return lastModified;
				}
			} else {
				getLogger()
						.error(MessageFormat
								.format("URL connection for the URI [{0}] is not a HTTP or HTTPS connection, can't read the [Last-Modified] header.",
										uri));
			}
		} catch (IOException ioex) {
			getLogger()
					.error(MessageFormat.format(
							"Error opening the URL connection for the URI [{0}].",
							uri), ioex);
		}
	} catch (MalformedURLException murlex) {
		getLogger().error(MessageFormat.format("URI [{0}].", uri), murlex);
	}
	getLogger()
			.warn(MessageFormat
					.format("Last modification of the URI [{0}] is not known.",
							uri));
	return null;
}