从html行中提取href的正确正则表达式是什么？ （JAVA）

Question

Hi I am trying to extract text which a href defines in a html line. For example:

<link rel="stylesheet" href="style.css" type="text/css">

I want to get "style.css" or:

<a href="target0.html"><img align="center" src="thumbnails/image001.jpg" width="154" height="99">

I want to get "target0.html"

What would be the correct Java code to do this?

Answer 1

    public static String getHref(String str)
    {
        int startIndex = str.indexOf("href=");
        if (startIndex < 0)
            return "";
        return str.substring(startIndex + 6, str.indexOf("\"", startIndex + 6));
    }

This method assumes that the html is well formed and it only works for the first href in the string but I'm sure you can extrapolate from here.

Answer 2

I realize you asked about using regular expressions, but jsoup makes this so simple and is much less error prone:

import java.io.IOException;

import nu.xom.ParsingException;
import nu.xom.ValidityException;

import org.jsoup.Jsoup;
import org.jsoup.nodes.Document;
import org.jsoup.nodes.Element;
import org.jsoup.select.Elements;
import org.xml.sax.SAXException;

public class HrefExtractor {
    public static void main(final String[] args) throws SAXException, ValidityException, ParsingException, IOException {
        final Document document = Jsoup.parse("<a href=\"target0.html\"><img align=\"center\" src=\"thumbnails/image001.jpg\" width=\"154\" height=\"99\">");
        final Elements links = document.select("a[href]");
        for (final Element element : links) {
            System.out.println(element.attr("href"));
        }
    }
}

Answer 3

I have not try the following but it should be something like this:

'Pattern.compile("<(?:link|a\\s+)[^>] href=\\"(. ?)\\"")'

But I'd recommend you to use one of available HTML or even XML parsers for this task.