9

I need to check whether a URL exists or not. I want to write a servlet for this i.e. to check whether a URL exists or not. If the URL entered does not exist, then it should return some message.

Glorfindel
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ha22109
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4 Answers4

26

Better solution for HTTP : 

public static boolean exists(String URLName){
    try {
      HttpURLConnection.setFollowRedirects(false);
      // note : you may also need
      //        HttpURLConnection.setInstanceFollowRedirects(false)
      HttpURLConnection con =
         (HttpURLConnection) new URL(URLName).openConnection();
      con.setRequestMethod("HEAD");
      return (con.getResponseCode() == HttpURLConnection.HTTP_OK);
    }
    catch (Exception e) {
       e.printStackTrace();
       return false;
    }
  }

If you are looking for any other URL try this code 

  public static boolean exists(String URLName){
      boolean result = false;
      try {
          url = new URL("ftp://ftp1.freebsd.org/pub/FreeBSD/");
          //url = new URL("ftp://ftp1.freebsd.org/pub/FreeBSD123/");//this will fail

          input = url.openStream();

           System.out.println("SUCCESS");
           result = true;

            } catch (Exception ex) {
               Logger.getLogger(NewClass.class.getName()).log(Level.SEVERE, null, ex);
            }
         return result;
  }

Source :http://www.rgagnon.com/javadetails/java-0059.html

jmj
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    `http` is not the only protocol/scheme in an URL. – Michael Konietzka Nov 14 '10 at 15:00
  • @Michael Konietzka Update probably answers your comment – jmj Nov 14 '10 at 16:05
  • I need to use Httpclient and its methods to check for url existence can u please tell how to use httpClient service.I tried to write this service in one servelt but it is giving exception. – ha22109 Nov 14 '10 at 16:46
  • @ha22109 if you are only concern with HTTP then first code should work for you perfectly – jmj Nov 14 '10 at 16:53
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    what about `mailto:example@example.com`? – Michael Konietzka Nov 14 '10 at 17:02
  • @Michael Konietzka by URL I mean address to some resource above can't be checked for validity ,in such cases you need to contact @example.com – jmj Nov 14 '10 at 17:14
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    but is is a valid URL which exists. ;-) – Michael Konietzka Nov 14 '10 at 17:16
  • @Michael Konietzka OP is just concern about HTTP protocol :) it is not given in requirement list ;) – jmj Nov 14 '10 at 17:18
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    I cannot see this in the requirements. ;-) OP is talking from URLs in general. ;-). Additionally the interpretation of `exist` is not clear. What does existence of a URL mean? From my point of view, the URL already exists when I write it down resp create it. Maybe the OP just wanted to know if an HTTP-Resource represented by a HTTP-URL would be accessible for him, but that was not what the OP asked. ;-) – Michael Konietzka Nov 14 '10 at 17:37
  • @Michael Konietzka from the comment of OP in the same thread it is clear that he wants to ask about HTTP protocol only, he has asked it globally actually – jmj Nov 14 '10 at 17:39
  • @org.life.java: My last comment contained some ironic note based on my sunday evening mood, which was lost when transporting via HTTP. ;-) – Michael Konietzka Nov 14 '10 at 18:03
2

You could try HTTP's HEAD method to see if the server returns a status code of 200 on a particular URL and act accordingly.

See http://en.wikipedia.org/wiki/Hypertext_Transfer_Protocol and scroll down to the Request Methods.

aefxx
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0

You can make a connection, get the input stream back, and check for null.

duffymo
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-3

I used this bash script for check urls, but need put all files in a file "urls.csv"

#!/bin/bash

###############################################
# mailto: ggerman@gmail.com
# checkurls
# https://github.com/ggerman/checkurls/
# require curl
###############################################

url() {
  cat urls.csv | 
  replace  | 
  show
}

replace() {
  tr ',' ' '
}

show() {
  awk '{print $1}'
}

url | \
while read CMD; do
  echo $CMD
  curl -Is $CMD | head -n 1
done
ggerman
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