Java Regular Expression to find CSS import in HTML file

Question

I'm working on building a Java program that will download a copy of a website to a local machine while maintaining the original file hierarchy.

I'm using the following: To find CSS of form http://www.w3schools.com/css/css_howto.asp (note working)

private static final String HTML_CSS_TAG_PATTERN = "\\s*(?i)href\\s*=\\s*(\"([^\"]*\")|'[^']*'|([^'\">\\s]+))";
private static final String CSS_TAG_PATTERN = "(?i)<link([^>]+)>(.+?)>";

To find images (working fine):

private static final String HTML_IMG_TAG_PATTERN = "\\s*(?i)src\\s*=\\s*(\"([^\"]*\")|'[^']*'|([^'\">\\s]+))";
private static final String IMG_TAG_PATTERN = "(?i)<img([^>]+)>(.+?)>";

To find links of form http://www.w3schools.com/html/html_links.asp (working fine)

private static final String HTML_A_HREF_TAG_PATTERN = "\\s*(?i)href\\s*=\\s*(\"([^\"]*\")|'[^']*'|([^'\">\\s]+))";
private static final String HTML_A_TAG_PATTERN = "(?i)<a([^>]+)>(.+?)</a>";

The link and images are working fine, but the CSS file isn't. I would like it to extract the link to the CSS file so that I can save it. Could anyone help me with what I missed?

What's wrong with just using a HTML parser like jsoup.org? Why trying it the overcomplicated and error prone way? — BalusC
– BalusC, Commented Dec 3, 2013 at 1:54

andyf · Accepted Answer · 2013-12-03 01:37:38Z

1

Try: CSS_TAG_PATTERN

<link[^>]+?text/css[^>]*?>

will match

<link rel="stylesheet" type="text/css" href="//cdn.sstatic.net/stackoverflow/all.css?v=0eb8b68aff29">

answered Dec 3, 2013 at 1:37

andyf

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3 Comments

user2680842 Over a year ago

It's throwing the following error: Exception in thread "main" java.lang.IndexOutOfBoundsException: No group 1 at java.util.regex.Matcher.group(Unknown Source) at CSSRegEx.grabHTMLLinks(CSSRegEx.java:42) at HTML.main(HTML.java:63) I think that means that it's finding the reference to the CSS, but there is still a mistake in CSS_TAG_PATTERN?

andyf Over a year ago

what is expected in group 1?

thedapperdev Over a year ago

stackoverflow.com/questions/1732348/…

chili_h · Accepted Answer · 2013-12-03 01:51:18Z

0

To make sure you only get CSS stylesheets try following CSS_TAG_PATTERN:

<link.*\s+rel="stylesheet"([^>]+)>

This pattern will match the following two

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

but not

    <link type="text/css" rel="license"  href="someStuff">

answered Dec 3, 2013 at 1:51

chili_h

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1 Comment

user2680842 Over a year ago

I'm not sure what you mean.

Abhishek Anand · Accepted Answer · 2013-12-03 02:47:24Z

0

Try this pattern

<link[.]+?text/css[.]*?>

It will match

<link rel="stylesheet" type="text/css" href="theme.css">
<link type="text/css" rel="stylesheet"  href="theme.css">
<link type="text/css" rel="license"  href="someStuff">

answered Dec 3, 2013 at 2:47

Abhishek Anand

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