basicnetworkstatus.java

来自「world wind java sdk 源码」· Java 代码 · 共 423 行 · 第 1/2 页

     * unavailability count is effectively set to 0.
     *
     * @param url a url containing the host to mark as available.
     */
    public synchronized void logAvailableHost(URL url)
    {
        if (this.offlineMode)
            return;

        if (url == null)
        {
            String message = Logging.getMessage("nullValue.URLIsNull");
            Logging.logger().severe(message);
            throw new IllegalArgumentException(message);
        }

        String hostName = url.getHost();
        HostInfo hi = this.hostMap.get(hostName);
        if (hi != null)
        {
            this.hostMap.remove(hostName); // host is available again
            firePropertyChange(NetworkStatus.HOST_AVAILABLE, null, url);
        }

        this.lastAvailableLogTime.set(System.currentTimeMillis());
    }

    /**
     * Indicates whether the host has been marked as unavailable. To be marked unavailable a host's attempt count must
     * exceed the specified attempt limit.
     *
     * @param url a url containing the host to check for availability.
     * @return true if the host is marked as unavailable, otherwise false.
     */
    public synchronized boolean isHostUnavailable(URL url)
    {
        if (this.offlineMode)
            return true;

        if (url == null)
        {
            String message = Logging.getMessage("nullValue.URLIsNull");
            Logging.logger().severe(message);
            throw new IllegalArgumentException(message);
        }

        String hostName = url.getHost();
        HostInfo hi = this.hostMap.get(hostName);
        if (hi == null)
            return false;

        if (hi.isTimeToTryAgain())
        {
            hi.logCount.set(0); // info removed from table in logAvailableHost
            return false;
        }

        return hi.isUnavailable();
    }

    /**
     * Indicates whether a public network can be reached or has been reached in the previous five seconds.
     *
     * @return false if the network can be reached or has been reached in the previous five seconds, otherwise true.
     */
    public boolean isNetworkUnavailable()
    {
        return this.offlineMode || this.isNetworkUnavailable(5000L);
    }

    /**
     * Indicates whether a public network can be reached or has been reached in a specified previous amount of time.
     *
     * @param checkInterval the number of milliseconds in the past used to determine whether the server was avaialble
     *                      recently.
     * @return false if the network can be reached or has been reached in a specified time, otherwise true.
     */
    public synchronized boolean isNetworkUnavailable(long checkInterval)
    {
        if (this.offlineMode)
            return true;

        // If there's been success since failure, network assumed to be reachable.
        if (this.lastAvailableLogTime.get() > this.lastUnavailableLogTime.get())
        {
            this.lastNetworkUnavailableResult.set(false);
            return this.lastNetworkUnavailableResult.get();
        }

        long now = System.currentTimeMillis();

        // If there's been success recently, network assumed to be reachable.
        if (!this.lastNetworkUnavailableResult.get() && now - this.lastAvailableLogTime.get() < checkInterval)
        {
            return this.lastNetworkUnavailableResult.get();
        }

        // If query comes too soon after an earlier one that addressed the network, return the earlier result.
        if (now - this.lastNetworkCheckTime.get() < checkInterval)
        {
            return this.lastNetworkUnavailableResult.get();
        }

        this.lastNetworkCheckTime.set(now);

        if (!this.isWorlWindServerUnavailable())
        {
            this.lastNetworkUnavailableResult.set(false); // network not unreachable
            return this.lastNetworkUnavailableResult.get();
        }

        for (String testHost : networkTestSites)
        {
            if (isHostReachable(testHost))
            {
                {
                    this.lastNetworkUnavailableResult.set(false); // network not unreachable
                    return this.lastNetworkUnavailableResult.get();
                }
            }
        }

        if (now - this.lastNetworkStatusReportTime.get() > NETWORK_STATUS_REPORT_INTERVAL)
        {
            this.lastNetworkStatusReportTime.set(now);
            String message = Logging.getMessage("NetworkStatus.NetworkUnreachable");
            Logging.logger().info(message);
        }

        this.lastNetworkUnavailableResult.set(true); // if no successful contact then network is unreachable
        return this.lastNetworkUnavailableResult.get();
    }

    /**
     * Indicates whether the NASA World Wind servers can be reached.
     *
     * @return false if the servers can be reached, otherwise true.
     */
    public boolean isWorlWindServerUnavailable()
    {
        return this.offlineMode || !isHostReachable("worldwind.arc.nasa.gov");
    }

    private static boolean isHostReachable(String hostName)
    {
        try
        {
            // Assume host is unreachable if we can't get its dns entry without getting an exception
            //noinspection ResultOfMethodCallIgnored
            InetAddress.getByName(hostName);
        }
        catch (UnknownHostException e)
        {
            String message = Logging.getMessage("NetworkStatus.UnreachableTestHost", hostName);
            Logging.logger().fine(message);
            return false;
        }
        catch (Exception e)
        {
            String message = Logging.getMessage("NetworkStatus.ExceptionTestingHost", hostName);
            Logging.logger().info(message);
            return false;
        }

        // Was able to get internet address, but host still might not be reachable because the address might have been
        // cached earlier when it was available. So need to try something else.

        URLConnection connection = null;
        try
        {
            URL url = new URL("http://" + hostName);
            Proxy proxy = WWIO.configureProxy();
            if (proxy != null)
                connection = url.openConnection(proxy);
            else
                connection = url.openConnection();

            connection.setConnectTimeout(2000);
            String ct = connection.getContentType();
            if (ct != null)
                return true;
        }
        catch (IOException e)
        {
            String message = Logging.getMessage("NetworkStatus.ExceptionTestingHost", hostName);
            Logging.logger().info(message);
        }
        finally
        {
            if (connection != null && connection instanceof HttpURLConnection)
                ((HttpURLConnection) connection).disconnect();
        }

        return false;
    }
//
//    public static void main(String[] args)
//    {
//        try
//        {
//            NetworkStatus ns = new BasicNetworkStatus();
//            boolean tf = ns.isWorlWindServerUnavailable();
//            tf = ns.isNetworkUnavailable();
//        }
//        catch (Exception e)
//        {
//            e.printStackTrace();
//        }
//    }
}