Reg exp in form

Question

Hello,
I need some help on reg expressions.
I want to allow users to type a url on my html page. The way I currently handle this situations is this:
myString = myString.replaceAll("(?:https?|ftp)://\\S+(?<![,.?!)])", "<a href=\"$0\">$0</a>");
so when the user types in a url such as http://www.java.sun it would display it back as a url that he/she can click on. This part works fine
However, if the user types in something like this:
<img src="http://www.someUrl.com/img.gif"/> it fails. In this case the user should see the image but he/she does not.
How can I make sure that only those instances get replaced where only URL is typed which is not part of other html. Should I add blank spaces before and after the url?
Thank you.

Answer 1

Will there be any links in the source document that are already in the processed format? That is, http://www.somewhere.org/If so, you'll need to match the whole element so don't accidentally match a URL within it. Then you can deal with the situation you brought up, where a start tag has a URL attribute. For that, just match any complete start tag and plug it back in. That should take care of any URL's that are contained within larger structures, leaving only "naked" URL's that need to be processed.
A simple replaceAll() won't work here, because you're doing different things with the text depending on what was matched. The Matcher class provides lower-level operations that let you do that kind of thing, but Elliott Hughes has written a nice little utility called Rewriter that does most of the work for you. Here's how you might use it:     String regex = "(?is)"  // CASE-INSENSITIVE and DOTALL modes
                + "<a\\s[^>]++>.*?</a>"  // a complete A element
                + "|"                    // or
                + "<[a-z]+\\s[^>]++>"    // a start tag with attributes
                + "|"                    // or
                + "(?:https?|ftp)://\\S+(?<![,.?!)])";  // a URL
    Rewriter rewriter = new Rewriter(regex)
      public String replacement()
        String found = group(0);
        return found.startsWith("<") ? found :
            "<a href=\"" + found + "\">" + found + "</a>";
    String resultStr = rewriter.rewrite(args[0]);