Regex to add tag before

Question

I need to write a util to add a tag before any

Test string points to <p><a href="http://www.acdevents.com/au2005/">Acd Event</a> with an image <a href="http://www.acdevents.com"><img src="image.jpg"></a>

This needs to be changed to

Test string points to <p><span class="test_class"><a href="http://www.acdevents.com/au2005/">Acd Event</a></span> with an image <a href="http://www.acdevents.com"><img src="image.jpg"></a>

As you can see the tag needs to be added only in case of a url pointing to a physical page and not if its an image.

I was planning to use regex to achieve this, but w/o any luck so far.

Any pointer on this will be highly appeciated.

-Thanks

Trying to do this with a regex sounds painful. Maybe you could use [XSLT](http://www.w3schools.com/xsl/)? Are you working with well-formed HTML documents, or tags embedded in plain text (like in the example)? — Brandon Bohrer, Mar 17 '11 at 21:47
regex + html = pain. Use DOM instead: http://stackoverflow.com/questions/3524431/wrap-dom-element-in-another-dom-element-in-php — Marc B, Mar 17 '11 at 21:47
I'm feeling the pain of using regex but there's no other way out. For some weird reason, I'm receiving html bosy text as String from a different service. I need to do some formatting and pre-processing, part of which is the question I had put. There's no scope for a XSLT. — Shamik, Mar 17 '11 at 21:55
I agree with Brandon: regular expressions aren't the right tool for the job. I'd advise the use of a parser such as John Cowan's 'TagSoup' to write some code to filter the HTML. If you prefer something more DOM-like than SAX-like, there's NekoHTML. — Keith Gaughan, Mar 17 '11 at 21:55

Keith Gaughan · Accepted Answer · 2011-03-17T22:29:29.597

Turning my comment into an answer, regular expressions aren't the right tool for the job. I'd advise the use of a parser such as John Cowan's 'TagSoup' to write some code to filter the HTML. If you prefer something more DOM-like than SAX-like, there's NekoHTML.

If you're absolutely certain you want to go down the regular expression route and you're using PCRE or another regex engine that supports look-ahead, you can use assertions, thus this regex may do the job for you:

s.replaceAll("<a[^>]*?>(?!<img.*)(.+?)</a>", "<span class=\"test_class\">$0</span>");

I haven't tested that, but the gist is correct. The important thing there is (?!<img.*), which asserts that you don't want to match <img followed by anything at that position. That may do the job for you, but I'm still of the opinion that a little bit of parsing is the best route.

Thanks Keith for taking the time. Your solution works like a charm. I agree with you that parser is the best solution. Having said that,I'm receiving this string without any html or a body tag, though it's supposed to represent the body content. It doesn't conform to the standards either.I think, most of the parsers will fail during the parse time.On top of that,its a fairly small size String with a few occurrence of tags, which kind of prompted me to take the regex route. Thanks a bunch for your help, appreciate it. — Shamik, Mar 17 '11 at 22:38

Adam Ayres · Answer 2 · 2011-03-17T22:19:16.933

1

If you have a library like jQuery on the page you could do it with something like this:

$("a").wrap("<span class='test_class' />");

Or if you need to do some check against the URL first:

$("a").each(function(){ 
    var element = $(this);
    var href = element.attr("href");
    if (href.indexOf("http://someUrl") > -1){ 
        element..wrap("<span class='test_class' />");
    }
});

If you don't have jQuery you could do it like this:

var elements = document.body.getElementsByTagName("a");
for (var i = 0; i < elements.length; i++) {
    var element = elements[i];
    var clone = element.cloneNode(true);
    var parent = element.parentNode;

    var span = document.createElement("span");
    span.setAttribute("class", "test_class");
    span.appendChild(clone);
    parent.replaceChild(span, element); 
}

You could do something very similar in Java using the Document interface:

DocumentBuilder builder = DocumentBuilderFactory.newDocumentBuilder();
Document doc = builder.parse(yourJavaHtmlString);
NodeList nodes = doc.getElementsByTagName("a");
for (int i = 0; i < nodes.getLength(); i++) {
    Element element = (Element) nodes.item(i);
    String href = element.getAttribute("href");
    if (!href.equals("http://www.acdevents.com")) {
        Element clone = element.cloneNode(true);
        Element parent = element.getParentNode();

        Element span = doc.createElement("span");
        span.setAttribute("class", "test_class");
        span.appendChild(clone);
        parent.replaceChild(span, element);
    }
}

edited Mar 17 '11 at 22:19

answered Mar 17 '11 at 21:49

Adam Ayres

8,732
1
32
25

OP did say 'java', though, so I'd assume the wrapping should be done server-side, which precludes javascript. – Marc B Mar 17 '11 at 21:51
Thanks Adam .. unfortunately this needs to happen in a java code. – Shamik Mar 17 '11 at 21:53
Sorry, missed that you wanted it in Java – Adam Ayres Mar 17 '11 at 21:56
I tried the following regex which works well for adding , but I'm not able to filter for the image href. This is adding the all all tags. testStr.replaceAll("]*>(.+?)","$0"); – Shamik Mar 17 '11 at 22:02
I added how the same thing could be done in Java using the Document interface in Java. – Adam Ayres Mar 17 '11 at 22:08
Thanks for the solution. I was primarily trying to void the parsing route since the input String (containing the html tags) is relatively small and occurrence is limited. I was more inclined to apply a quick regex solution. I'll try out the DOM route (referring your sample code) and apply the additional logic of ignoring applying the if is associating an image.Thanks for your help again. – Shamik Mar 17 '11 at 22:20

Regex to add tag before

2 Answers2