Question

I have a wysiwyg text area in a Java webapp. Users can input text and style it or paste some already HTML-formatted text.

What I am trying to do is to linkify the text. This means, converting all possible URLs within text, to their ‘working counterpart’, i.e. adding < a href=’…’>…< /a>.

This solution works when all I have is plain text:

String r = 'http(s)?://([\\w+?\\.\\w+])+([a-zA-Z0-9\\~\\!\\@\\#\\$\\%\\^\\&amp;\\*\\(\\)_\\-\\=\\+\\\\\\/\\?\\.\\:\\;\\'\\,]*)?'; Pattern pattern = Pattern.compile(r, Pattern.DOTALL | Pattern.UNIX_LINES | Pattern.CASE_INSENSITIVE); Matcher matcher = pattern.matcher(comment); comment = matcher.replaceAll('<a href=\'$0\'>$0</a>'); // group 0 is the whole expression 

But the problem is when there is some already formatted text, i.e. that it already has the < a href=’…’>…< /a> tags.

So I am looking for some way for the pattern not to match whenever it finds the text between two HTML tags (< a>). I have read this can be achieved with lookahead or lookbehind but I still can’t make it work. I am sure I am doing it wrong because the regex still matches. And yes, I have been playing around/ debugging groups, changing $0 to $1 etc.

Any ideas?

Answer 1

You are close. You can use a ‘negative lookbehind’ like so:

(?<!href=')http:// etc 

All results preceded by href will be ignored.