Xpath查找给定子项具有最大值的元素

Question

Here is the XML:

<root>
  <ACTS>
    <ACT>Play</ACT>
    <A>
      <Day>1</Day>
      <time>Fri Feb 28 13:21:42 IST 2014</time>
    </A>
    <A>
      <Day>2</Day>
      <time>Fri Feb 28 13:21:43 IST 2014</time>
    </A>    
  </ACTS>
  <ACTS>
    <ACT>Study</ACT>
    <A>
      <Day>1</Day>
      <time>Fri Feb 28 13:21:42 IST 2014</time>
    </A>
    <A>
      <Day>2</Day>
      <time>Fri Feb 28 13:21:43 IST 2014</time>
    </A> 
    <A>
      <Day>3</Day>
      <time>Fri Feb 28 13:21:43 IST 2014</time>
    </A>   
  </ACTS>
</root>

How can I find the element A and its children for ACT = 'Study' for which the value of Day is maximum? Here is the Java program:

String xp = "//ACTS[ACT='Study']/A[not(Day < //ACTS[ACT='Study']/A/Day)]";
XPathExpression expr = xpath.compile(xp);
NodeList nl = (NodeList) expr.evaluate(doc, XPathConstants.NODESET);
if (null != nl && null != nl.item(0)) {
    String abc = nl.item(0).getChildNodes().item(0).getNodeValue();
    System.out.println(abc);
}

Note: With this XPath I am able to get the maximum value for Day by

NodeList nl = (NodeList) expr.evaluate(doc, XPathConstants.NODESET);
if (null != nl && null != nl.item(0)) {
    maxAttemptNumber = nl.item(0).getTextContent();
} 

but need help in getting element A and its children.

Answer 1

If you're using Java, then you can use XQuery as easily as XPath 2.0 or XPath 1.0 (eg with the Saxon library). The answer is then

(for $a in //ACTS[ACT="Study"]/A
order by number($a/Day))[last()]