How to add external CSS to HTML 'style'

Question

How can I convert an external CSS style sheet into the 'style' section of my HTML using Java?

I want to be able to have my external CSS exist in the 'style' section so that I can parse it to inline styles rather than external and the easiest way I have seen to do this is to have the CSS directly in the HTML rather than linked.

I would like to change this in my HTML:

<link rel="stylesheet" href="smartdoc.css" />

To this (Ideally by passing the CSS file as an argument for a method):

<style>
    Content from external CSS.
</style>

So that I can apply JSoup to convert it to inline style using something like this:

public static String inlineCss(String html) {
final String style = "style";
Document doc = Jsoup.parse(html);
Elements els = doc.select(style);// to get all the style elements
for (Element e : els) {
  String styleRules = e.getAllElements().get(0).data().replaceAll("\n", "").trim();
  String delims = "{}";
  StringTokenizer st = new StringTokenizer(styleRules, delims);
  while (st.countTokens() > 1) {
    String selector = st.nextToken(), properties = st.nextToken();
    if (!selector.contains(":")) { // skip a:hover rules, etc.
      Elements selectedElements = doc.select(selector);
      for (Element selElem : selectedElements) {
        String oldProperties = selElem.attr(style);
        selElem.attr(style,
            oldProperties.length() > 0 ? concatenateProperties(
                oldProperties, properties) : properties);
      }
    }
  }
  e.remove();
}
return doc.toString();
}

private static String concatenateProperties(String oldProp, @NotNull String newProp) {
oldProp = oldProp.trim();
if (!oldProp.endsWith(";"))
  oldProp += ";";
return oldProp + newProp.replaceAll("\\s{2,}", " ");
}

Any suggestions for this?

Stephan · Accepted Answer · 2016-09-02 09:32:57Z

I assume that all your files are on a local hard drive encoded in UTF-8.

dummy.html

<link rel="stylesheet" href="smartdoc.css" />

smartdoc.css

a {
  background-color: red;
}

p {
  background-color: green;
}

SAMPLE CODE

To replace the link node with the CSS file content, do the following:

// Load HTML file
String charsetName = "UTF-8";
Document doc = Jsoup.parse(new File("dummy.html"), charsetName);
System.out.println("BEFORE:\n" + doc.outerHtml());

// Replace each link nodes with its respective CSS file content
for (Element link : doc.select("link[rel=stylesheet]")) {
    String cssFilename = link.attr("href");

    Element style = new Element(Tag.valueOf("style"), "");
    style.appendText("/* " + cssFilename + " */");
    style.appendText(loadCssFileContent(cssFilename, charsetName));

    link.replaceWith(style);
}

System.out.println("\nAFTER:\n" + doc.outerHtml());

private static String loadCssFileContent(String path, String charsetName) throws IOException {
    byte[] encoded = Files.readAllBytes(Paths.get(path));
    return new String(encoded, charsetName);
}

OUTPUT

BEFORE:
<html>
 <head>
  <link rel="stylesheet" href="smartdoc.css">
 </head>
 <body></body>
</html>

AFTER:
<html>
 <head>
  <style>/* smartdoc.css */a { background-color: red; } p { background-color: green; }</style>
 </head>
 <body></body>
</html>

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