如何在javax XPath中写入日期转换条件？

Question

My XML is:

<?xml version="1.0"?>
<company>
    <staff id="1001" thedate="2013-01-01">
        <firstname>yong</firstname>
        <lastname>mook kim</lastname>
        <nickname>mkyong</nickname>
        <salary>100000</salary>
    </staff>
    <staff id="2001" thedate="2014-01-01">
        <firstname>low</firstname>
        <lastname>yin fong</lastname>
        <nickname>fong fong</nickname>
        <salary>200000</salary>
    </staff>
</company>

I need a java code, which can compare dates from XML. I wrote this java code, but it does not work:

public static void main(String[] args) {
    try {
        File fXmlFile = new File("c:\\tmp\\test.xml");
        DocumentBuilderFactory dbFactory = DocumentBuilderFactory.newInstance();
        DocumentBuilder dBuilder;
        dBuilder = dbFactory.newDocumentBuilder();
        Document doc = dBuilder.parse(fXmlFile);
        NodeList nList = doc.getElementsByTagName("staff");
        for (int temp = 0; temp < nList.getLength(); temp++) {
            Node nNode = nList.item(temp);
            String exp = "xs:date(@thedate) &gt; xs:date('2013-05-01')"; //here comes the expression, but it does not work
            System.out.println(selectBooleanValue(nNode,exp));
        }
    } catch (Exception e) {
        e.printStackTrace();
    }
}
private static boolean selectBooleanValue(Node node, String xpathString) {
    try {
        XPath xpath = XPATH_FACTORY.get().newXPath();
        XPathExpression expr = xpath.compile(xpathString);
        boolean result = Boolean.valueOf(expr.evaluate(node, XPathConstants.BOOLEAN).toString());
        return result;
    } catch (XPathExpressionException e) {
        return false;
    }
}
private static ThreadLocal<XPathFactory> XPATH_FACTORY = new ThreadLocal<XPathFactory>() {
    @Override
    protected XPathFactory initialValue() {
        return XPathFactory.newInstance();
    };
};

I always get "false, false" output, so it does not work. The corresponding output would be: "false, true"

This line is the main question here:

String exp = "xs:date(@thedate) > xs:date('2013-05-01')"; //here comes the expression, but it does not work

I tried without xs: but it is also does not work. I know there are other ways, but I need to solve this problem with that line! What kind of expression should I use to compare date values which are String variables actually?

I tried my code to compare strings, and it is works with it, but I need to compare dates!

Thank you!

Answer 1

XPath 2.0 which you seem to use has two greater than comparison operators, one is > , the other is gt . So try the expression xs:date(@thedate) > xs:date('2013-05-01') or the expression xs:date(@thedate) gt xs:date('2013-05-01') . > is only used inside XSLT code to make sure the code is following XML rules, that is not something needed in pure XPath. But I wonder whether you use an XPath 2.0 implementation at all and whether you also do not need to set up a namespace resolver to map the xs prefix to the XML schema namespace.

Assuming you have the Java built-in XPath 1.0 implementation all you can do is compare numbers so you could use number(translate(@thedate, '-', '')) > 20130501 .