Preferred Java way to ping an HTTP URL for availability

Question

I need a monitor class that regularly checks whether a given HTTP URL is available  I can take care of the  regularly  part using the Spring TaskExecutor abstraction  so that s not the topic here  The question is  What is the preferred way to ping a URL in java   Here is my current code as a starting point   try       final URLConnection connection   new URL url  openConnection        connection connect        LOG info  Service     url     available  yeah         available   true    catch  final MalformedURLException e        throw new IllegalStateException  Bad URL      url  e     catch  final IOException e        LOG info  Service     url     unavailable  oh no    e       available   false       Is this any good at all  will it do what I want   Do I have to somehow close the connection  I suppose this is a GET request  Is there a way to send HEAD instead

User · Answer

Instead of using URLConnection use HttpURLConnection by calling openConnection() on your URL object.

Then use getResponseCode() will give you the HTTP response once you've read from the connection.

here is code:

    HttpURLConnection connection = null;
    try {
        URL u = new URL("http://www.google.com/");
        connection = (HttpURLConnection) u.openConnection();
        connection.setRequestMethod("HEAD");
        int code = connection.getResponseCode();
        System.out.println("" + code);
        // You can determine on HTTP return code received. 200 is success.
    } catch (MalformedURLException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    } catch (IOException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    } finally {
        if (connection != null) {
            connection.disconnect();
        }
    }

Also check similar question How to check if a URL exists or returns 404 with Java?

Hope this helps.

User · Answer

here the writer suggests this   public boolean isOnline         Runtime runtime   Runtime getRuntime        try           Process ipProcess   runtime exec   system bin ping -c 1 8 8 8 8            int     exitValue   ipProcess waitFor            return  exitValue    0         catch  IOException   InterruptedException e    e printStackTrace          return false      Possible Questions   Is this really fast enough Yes  very fast  Couldn   t I just ping my own page  which I want to request anyways  Sure  You could even check both  if you want to differentiate between    internet connection available    and your own servers beeing reachable What if the DNS is down  Google DNS  e g  8 8 8 8  is the largest public DNS service in the world  As of 2013 it serves 130 billion requests a day  Let    s just say  your app not responding would probably not be the talk of the day    read the link  its seems very good  EDIT  in my exp of using it  it s not as fast as this method   public boolean isOnline         NetworkInfo netInfo   connectivityManager getActiveNetworkInfo        return netInfo    null  amp  amp  netInfo isConnectedOrConnecting        they are a bit different but in the functionality for just checking the connection to internet the first method may become slow due to the connection variables

User · Answer

Consider using the Restlet framework  which has great semantics for this sort of thing  It s powerful and flexible   The code could be as simple as   Client client   new Client Protocol HTTP   Response response   client get url   if  response getStatus   isError             uh oh

User · Answer

You could also use HttpURLConnection  which allows you to set the request method  to HEAD for example    Here s an example that shows how to send a request  read the response  and disconnect

User · Answer

Is this any good at all  will it do what I want     You can do so  Another feasible way is using java net Socket   public static boolean pingHost String host  int port  int timeout        try  Socket socket   new Socket              socket connect new InetSocketAddress host  port   timeout           return true        catch  IOException e            return false     Either timeout or unreachable or failed DNS lookup            There s also the InetAddress isReachable     boolean reachable   InetAddress getByName hostname  isReachable      This however doesn t explicitly test port 80  You risk to get false negatives due to a Firewall blocking other ports        Do I have to somehow close the connection    No  you don t explicitly need  It s handled and pooled under the hoods        I suppose this is a GET request  Is there a way to send HEAD instead    You can cast the obtained URLConnection to HttpURLConnection and then use setRequestMethod   to set the request method  However  you need to take into account that some poor webapps or homegrown servers may return HTTP 405 error for a HEAD  i e  not available  not implemented  not allowed  while a GET works perfectly fine  Using GET is more reliable in case you intend to verify links resources not domains hosts        Testing the server for availability is not enough in my case  I need to test the URL  the webapp may not be deployed    Indeed  connecting a host only informs if the host is available  not if the content is available  It can as good happen that a webserver has started without problems  but the webapp failed to deploy during server s start  This will however usually not cause the entire server to go down  You can determine that by checking if the HTTP response code is 200   HttpURLConnection connection    HttpURLConnection  new URL url  openConnection    connection setRequestMethod  HEAD    int responseCode   connection getResponseCode    if  responseCode    200           Not OK         lt  100 is undetermined     1nn is informal  shouldn t happen on a GET HEAD     2nn is success    3nn is redirect    4nn is client error    5nn is server error   For more detail about response status codes see RFC 2616 section 10  Calling connect   is by the way not needed if you re determining the response data  It will implicitly connect    For future reference  here s a complete example in flavor of an utility method  also taking account with timeouts          Pings a HTTP URL  This effectively sends a HEAD request and returns  lt code gt true lt  code gt  if the response code is in     the 200-399 range      param url The HTTP URL to be pinged      param timeout The timeout in millis for both the connection timeout and the response read timeout  Note that    the total timeout is effectively two times the given timeout      return  lt code gt true lt  code gt  if the given HTTP URL has returned response code 200-399 on a HEAD request within the    given timeout  otherwise  lt code gt false lt  code gt       public static boolean pingURL String url  int timeout        url   url replaceFirst   https    http       Otherwise an exception may be thrown on invalid SSL certificates       try           HttpURLConnection connection    HttpURLConnection  new URL url  openConnection            connection setConnectTimeout timeout           connection setReadTimeout timeout           connection setRequestMethod  HEAD            int responseCode   connection getResponseCode            return  200  lt   responseCode  amp  amp  responseCode  lt   399         catch  IOException exception            return false

User · Answer

The following code performs a HEAD request to check whether the website is available or not   public static boolean isReachable String targetUrl  throws IOException       HttpURLConnection httpUrlConnection    HttpURLConnection  new URL              targetUrl  openConnection        httpUrlConnection setRequestMethod  HEAD         try               int responseCode   httpUrlConnection getResponseCode             return responseCode    HttpURLConnection HTTP OK        catch  UnknownHostException noInternetConnection                return false

[java] Preferred Java way to ping an HTTP URL for availability

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