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Exception: no protocol ...

Posted on 2004-10-10
Medium Priority
Last Modified: 2012-06-21
Hey everyone,
I've basically made a program that, basically; let's you/the user know whether the links on a webpage have changed/(new ones added/old ones removed).

Here's the code:

//:::::::::::::::::::::::::::::::::::::::  DomainChangeCheck.java :::::::::::::::::::::::::::::::::::::::::\\
import java.io.*;
import java.util.*;
import java.net.*;
import javax.swing.text.html.*;
import javax.swing.text.*;
import java.text.*;

public class DomainChangeCheck {
      static String sDomain = "";
      static String sPage   = "";
      static int http       = 80;
      public static void main ( String [] args ) {
            DomainChangeCheck dcc = new DomainChangeCheck ();
            // Verify that an argument has been passed:
            if ( args.length == 0 ) {
                  System.out.println("Usage: java EeJavaInformer www.domain.com/page.htm");
                  System.exit( 1 );
            String s1 = "",
                     s2 = "";
            sDomain = args[0];
            if ( args[1].length() > 0 ) sPage = args[1];
            // Verify domain existance:
            boolean exist = false;
          try {
              InetAddress addr = InetAddress.getByName( sDomain );
              // This constructor will block until the connection succeeds
              Socket socket = new Socket(addr, http);
              exist = true;
          } catch (Exception e) {      }
          // Exit if domain does not exist.
          if ( /*domain does not*/ !exist ) {
                System.out.println( "Domain: " + sDomain + " cannot be found." );
                System.exit( 1 );
            boolean bFirstTime = true;
      for (;;) {
            s2 = s1;
          // Retrieve all links in HTML document:
          String [] links = dcc.getLinks( "http://" + sDomain + sPage );
          if ( links.length == 0) {
                System.out.println( "Error: Could not find any links in specified document" );
                System.exit( 1 );
          s1 = "";
          // Check to see if any changes to the links on the page have been made:
          for ( int i=0; i<links.length; i++ ) {
                s1 += links[i];
          if ( !(dcc.doDiff( s1, s2 )) ) {
                if ( bFirstTime ) {
                      System.out.println( "\nStarted Successfully..." );
                      bFirstTime = false;
                } else {
                      System.out.println( "\nA change to the page has been made." );
      private boolean doDiff ( String s1, String s2 ) {
            // return true if the two strings are the same. Else, false.
            if ( s1.length() != s2.length() ) return false;
            char [] c1 = s1.toCharArray();
            char [] c2 = s2.toCharArray();
            boolean bSame = true;
            for ( int i=0; i<c1.length; i++ ) {
                  if ( c1[i]!=c2[i] && bSame ) bSame = false;
            return bSame;
    public static String[] getLinks(String uriStr) {
        List result = new ArrayList();
        try {
            // Create a reader on the HTML content
            URL url = new URI(uriStr).toURL();
            URLConnection conn = url.openConnection();
            Reader rd = new InputStreamReader(conn.getInputStream());
            // Parse the HTML
            EditorKit kit = new HTMLEditorKit();
            HTMLDocument doc = (HTMLDocument)kit.createDefaultDocument();
            doc.putProperty("IgnoreCharsetDirective", new Boolean(true));
            kit.read(rd, doc, 0);
            // Find all the A elements in the HTML document
            HTMLDocument.Iterator it = doc.getIterator(HTML.Tag.A);
            while (it.isValid()) {
                SimpleAttributeSet s = (SimpleAttributeSet)it.getAttributes();
                String link = (String)s.getAttribute(HTML.Attribute.HREF);
                if (link != null) {
                    // Add the link to the result list
        } catch (Exception e) {
              System.out.println( "Exception: " + e.getMessage() + "\n" );
        // Return all found links
        return (String[])result.toArray(new String[result.size()]);
//:::::::::::::::::::::::::::::::::::::::  DomainChangeCheck.java :::::::::::::::::::::::::::::::::::::::::\\

Okay now; When I type something like:

java DomainChangeCheck www.positive-websolutions.co.uk /Index.htm

It works fine, but, let's assume that one puts:
java DomainChangeCheck www.experts-exchange.com /Java/

:o\ -- It doesn't work!! I get the following exception (from within the getLinks() method):
well, the  stackTrace:

java.net.MalformedURLException: no protocol: /Programming/Programming_Langauges/Java/

Any ideas why?

ThanQ :)
Question by:DrWarezz
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LVL 86

Expert Comment

ID: 12272005
Are you sure you're not calling getLinks from elsewhere and that the only code you're running is the code you posted?
LVL 86

Expert Comment

ID: 12272023
Also, instead of, or in addition to:

>>System.out.println( "Exception: " + e.getMessage() + "\n" );

could you do

System.err.println( "URI was " + uriStr );



Author Comment

ID: 12272141
I'm sure that all the code I'm running is what's been posted.

I inserted:
System.err.println( "URI was " + uriStr );
into it, and it outputs:

URI was http://www.experts-exchange.com/Java/

:o\ ?

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Author Comment

ID: 12272148
According to the stackTrace, it would seem that it's line 106 that the error is occuring on:

Reader rd = new InputStreamReader(conn.getInputStream());

LVL 86

Expert Comment

ID: 12272154
Yes but i'd like to see *all* the error output with that in it too ;-)

Author Comment

ID: 12272179
Okay, here's EVERYTHING that's outputted:

Exception: no protocol: /Programming/Programming_Languages/Java/

URI was http://www.experts-exchange.com/Java/
java.net.MalformedURLException: no protocol: /Programming/Programming_Languages/Java/
   at java.net.URL.(init)(URL.java.579)
   at java.net.URL.(init)(URL.java.476)
   at java.net.URL.(init)(URL.java.425)
   at sun.net.www.protocol.http.HttpURLConnection.followRedirect(HttpURLConnection.java:1090)
   at sun.net.www.protocol.http.HttpURLConnection.getInputStream(HttpURLConnection.java:681)
   at DomainChangeCheck.getLinks(DomanChangeCheck.java:106)
   at DomainChangeCheck.getLinks(DomanChangeCheck.java:55)
Error: Could not find any links in specified document

And here's the command I type:
java DomainChangeCheck www.experts-exchange.com /Java/

LVL 86

Accepted Solution

CEHJ earned 2000 total points
ID: 12272229
At the risk of repeating myself (i said this yesterday and was accused of being 'unhelpful') the html packages are pretty flaky and/or intolerant when it comes to parsing html, so you'll have to accept uneven results. That


does a redirect to


So if you were to enter http://www.experts-exchange.com/Programming/Programming_Languages/Java/ at the outset, you might have more success

Author Comment

ID: 12272240
lol - You were right! :D -- It's the redirection.

Thanks alot CEHJ :)
LVL 86

Expert Comment

ID: 12272245

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