Replace text by HTML links

[Elías Turbay]

Hi, sorry for my poor english

I need to replace any valid URL (Example: "https://coderanch.com") with an HTML link,

<a href='https://coderanch.com' rel='nofollow' rel="nofollow">www.coderanch.com</a>

I searched all over the net and I could not find the way to go generic.

I understand that I have to use regular expressions, but I have no experience with them.

Thanks in advance

[Sebastian Janisch]

Weird, the first result on google is this: http://geekswithblogs.net/casualjim/archive/2005/12/01/61722.aspx

[Elías Turbay]

Hi Sebastian

When I try to use it:

  String regExp = "^((ht|f)tp(s?)\:\/\/|~/|/)?([\w]+:\w+@)?([a-zA-Z]{1}([\w\-]+\.)+([\w]{2,5}))(:[\d]{1,5})?((/?\w+/)+|/?)(\w+\.[\w]{3,4})?((\?\w+=\w+)?(&\w+=\w+)*)?";  

I get the following errors :

Multiple markers at this line
- Syntax error on tokens, delete these tokens
- Syntax error on tokens, delete these tokens
- Syntax error, insert "AssignmentOperator Expression" to complete
Expression
- Invalid escape sequence (valid ones are \b \t \n \f \r \" \' \\ )
- Syntax error, insert ";" to complete BlockStatements
- Syntax error on tokens, delete these tokens
- The left-hand side of an assignment must be a variable

Can you help me with this?

[Elías Turbay]

I tried to remove all the invalid escape sequences:

String regExp = "^((ht|f)tp(s?)://|~/|/)?([w]+:w+@)?([a-zA-Z]{1}([w-]+.)+([w]{2,5}))(:[d]{1,5})?((/?w+/)+|/?)(w+.[w]{3,4})?((?w+=w+)?(&w+=w+)*)?";

But when I do:

  Pattern pattern = Pattern.compile(regExp);  

I get the following error:

    
Exception in thread "main" java.util.regex.PatternSyntaxException: Unknown inline modifier near index 109
^((ht|f)tp(s?)://|~/|/)?([w]+:w+@)?([a-zA-Z]{1}([w-]+.)+([w]{2,5}))(:[d]{1,5})?((/?w+/)+|/?)(w+.[w]{3,4})?((?w+=w+)?(&w+=w+)*)?
                                                                                                             ^

[Paul Clapham]

When you see a regex string (or any string, really) which contains backslashes, and you want to make a Java string literal out of it, you have to replace each \ by \\.

[Elías Turbay]

Tanks Paul.

Now I have this code, and it works fine...

	public static String generateLinks(String text) {
		String regExp = "^((ht|f)tps?\\:\\/\\/[a-zA-Z0-9_\\-]+(?:\\.[a-zA-Z0-9_\\-]+)*\\.[a-zA-Z]{2,4}(?:\\/[a-zA-Z0-9_]+)*(?:\\/[a-zA-Z0-9_]+\\.[a-zA-Z]{2,4}(?:\\?[a-zA-Z0-9_]+\\=[a-zA-Z0-9_]+)?)?(?:\\&[a-zA-Z0-9_]+\\=[a-zA-Z0-9_]+)*)$";
		String fFRAGMENT = "<a  rel='nofollow' rel="nofollow">$1</a>";
		
		Pattern pattern = Pattern.compile(regExp);
        Matcher matcher = pattern.matcher(text);

        return matcher.replaceAll(fFRAGMENT);
	}

But I need another thing and I don't know how to do it. For example:

  System.out.println( generateLinks("Bla bla bla bla https://coderanch.com bla bla bla") );  

And the result should be:

  Bla bla bla bla <a href='https://coderanch.com' rel='nofollow' rel="nofollow">www.coderanch.com</a> bla bla bla 

[Sebastian Janisch]

^ marks the beginning of a string literal, $ marks the end. Now do the math ;)

[Henry Wong]

I understand that I have to use regular expressions, but I have no experience with them.

I am really not a fan of this. IMO, if you don't have experience with regex, you should not start with complex regexes. Using code that you don't understand is never a good idea.

Get up to speed on regex. Use it for simple stuff til you get more comfortable. And in the meantime, I recommend that you just use the regular string methods such as substring(), charAt(), etc. You can always port it to regex later once you get better at it.

Henry

[Sege Stephen]

Elías Turbay wrote:Tanks Paul.

Now I have this code, and it works fine...

	public static String generateLinks(String text) {
		String regExp = "^((ht|f)tps?\\:\\/\\/[a-zA-Z0-9_\\-]+(?:\\.[a-zA-Z0-9_\\-]+)*\\.[a-zA-Z]{2,4}(?:\\/[a-zA-Z0-9_]+)*(?:\\/[a-zA-Z0-9_]+\\.[a-zA-Z]{2,4}(?:\\?[a-zA-Z0-9_]+\\=[a-zA-Z0-9_]+)?)?(?:\\&[a-zA-Z0-9_]+\\=[a-zA-Z0-9_]+)*)$";
		String fFRAGMENT = "<a  rel='nofollow' rel="nofollow">$1</a>";
		
		Pattern pattern = Pattern.compile(regExp);
        Matcher matcher = pattern.matcher(text);
        return matcher.replaceAll(fFRAGMENT);
	}

But I need another thing and I don't know how to do it. For example:

  System.out.println( generateLinks("Bla bla bla bla https://coderanch.com bla bla bla") );  

And the result should be:

  Bla bla bla bla <a href='https://coderanch.com' rel='nofollow' rel="nofollow">www.coderanch.com</a> bla bla bla 

Did you find a solution? Please post it, I want to solve the same problem to be displayed in a chat window

[Sean Clark]

^ marks the beginning of a string literal, $ marks the end. Now do the math ;)

Sebastian above give a big hint on how to solve this.

Please read the posts above.

Sean

[Rob Spoor]

You might want to try and find a copy of "Mastering Regular Expressions" by Jeff Friedl, as it handles this exact problem as an example. Perhaps you can find it at your local library.