com.google.android.apps.authenticator.timesync.NetworkTimeProvider.java Source code

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Here is the source code for com.google.android.apps.authenticator.timesync.NetworkTimeProvider.java

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/*
 * Copyright 2012 Google Inc. All Rights Reserved.
 *
 * Licensed 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.
 */

package com.google.android.apps.authenticator.timesync;

import android.util.Log;

import org.apache.http.Header;
import org.apache.http.HttpEntity;
import org.apache.http.HttpResponse;
import org.apache.http.client.ClientProtocolException;
import org.apache.http.client.HttpClient;
import org.apache.http.client.methods.HttpHead;
import org.apache.http.impl.cookie.DateParseException;
import org.apache.http.impl.cookie.DateUtils;

import java.io.IOException;
import java.util.Date;

/**
 * Provider of network time that obtains the time by making a network request to Google.
 *
 * @author klyubin@google.com (Alex Klyubin)
 */
public class NetworkTimeProvider {

    private static final String LOG_TAG = NetworkTimeProvider.class.getSimpleName();
    private static final String URL = "https://www.google.com";

    private final HttpClient mHttpClient;

    public NetworkTimeProvider(HttpClient httpClient) {
        mHttpClient = httpClient;
    }

    /**
     * Gets the system time by issuing a request over the network.
     *
     * @return time (milliseconds since epoch).
     *
     * @throws IOException if an I/O error occurs.
     */
    public long getNetworkTime() throws IOException {
        HttpHead request = new HttpHead(URL);
        Log.i(LOG_TAG, "Sending request to " + request.getURI());
        HttpResponse httpResponse;
        try {
            httpResponse = mHttpClient.execute(request);
        } catch (ClientProtocolException e) {
            throw new IOException(String.valueOf(e));
        } catch (IOException e) {
            throw new IOException("Failed due to connectivity issues: " + e);
        }

        try {
            Header dateHeader = httpResponse.getLastHeader("Date");
            Log.i(LOG_TAG, "Received response with Date header: " + dateHeader);
            if (dateHeader == null) {
                throw new IOException("No Date header in response");
            }
            String dateHeaderValue = dateHeader.getValue();
            try {
                Date networkDate = DateUtils.parseDate(dateHeaderValue);
                return networkDate.getTime();
            } catch (DateParseException e) {
                throw new IOException("Invalid Date header format in response: \"" + dateHeaderValue + "\"");
            }
        } finally {
            // Consume all of the content of the response to facilitate HTTP 1.1 persistent connection
            // reuse and to avoid running out of connections when this methods is scheduled on different
            // threads.
            try {
                HttpEntity responseEntity = httpResponse.getEntity();
                if (responseEntity != null) {
                    responseEntity.consumeContent();
                }
            } catch (IOException e) {
                // Ignored because this is not an error that is relevant to clients of this transport.
            }
        }
    }
}