chrsan/css-selectors

An implementation of the W3C Selectors Level 3 specification.

Overview

A Java implementation of the W3C Selectors Specification.

This README covers the API for version 2.x, see the wiki for the old API.

Selector matching

Selectors are matched against a node in a DOM. More specifically they are matched against a DOMNode which provides an abstraction over a concrete DOM implementation.

This library provides the W3CNode which wraps a org.w3c.dom.Node, but you could always roll your own.

For simple one off selector matching it's easiest to specify the selectors as a string:

Selectors selectors = new Selectors(new W3CNode(document));
List<Node> result = selectors.querySelectorAll("head > :not(meta)");
Node firstDiv = selectors.querySelector("div");

When matching selectors more than once, you'd benefit by parsing the selectors string into a selector list.

List<Selector> selectorList = Selectors.parse("head > :not(meta)");
Selectors selectors = new Selectors(new W3CNode(document));
List<Node> result = selectors.querySelectorAll(selectorList);
Node firstDiv = selectors.querySelector(selectorList);

Custom selector matching

This library provides the functionality that's specified in the spec, but it's possible to hook into the matching machinery by using an implementation of the SimpleSelectorMatcher interface. This implementation will then be used when no node could be matched using the default matching machinery.

Let's say that we liked the :contains() functional pseudo class that has been removed from the spec.

SimpleSelectorMatcher<W3CNode> matcher = new SimpleSelectorMatcher<W3CNode>() {
    @Override
    public boolean matches(SimpleSelector simpleSelector, W3CNode node) {
        if (!(simpleSelector instanceof PseudoFunctionSelector)) {
            return false;
        }

        PseudoFunctionSelector selector = (PseudoFunctionSelector) simpleSelector;
        if (!selector.name.equals("contains")) {
            return false;
        }

        String text = node.getUnderlying().getTextContent();
        return text != null && text.contains(selector.arguments);
    }
};

Selectors selectors = new Selectors(new W3CNode(document), matcher);
List<Node> result = selectors.querySelectorAll(":contains('Boom')");

Credit

Much of the inspiration for the 2.x rewrite came from the excellent CSS libraries that are used in Servo.