Simple, thread-safe xpath with namespace support

SimpleXPath.java

/**
 * Thread-safe xpath with namespace support.
 */
public class SimpleXPath {
    private final String expression;

    public SimpleXPath(String expression) {
        this.expression = expression;
    }

    public String evaluate(String xml) {
        return this.evaluate(new InputSource(new StringReader(xml)));
    }

    public String evaluate(InputSource source) {
        XPathFactory factory = XPathFactory.newInstance();
        XPath xpath = factory.newXPath();
        xpath.setNamespaceContext(MyNamespaceContext.getInstance());
        try {
            XPathExpression expr = xpath.compile(expression);
            return expr.evaluate(source);
        } catch (XPathExpressionException e) {
            throw new RuntimeException(e);
        }
    }
}

class MyNamespaceContext {
    
    private static SimpleNamespaceContext instance;
    
    static {
        instance = new SimpleNamespaceContext();
        instance.addNamespace("soap", "http://schemas.xmlsoap.org/soap/envelope/");
        // TODO: add your namespaces here
    }
    
    private MyNamespaceContext() {
    }

    public static NamespaceContext getInstance() {
        return instance;
    }
}