I would like to select the value of the first href attribute from documents

Question

0

Asked: May 17, 20262026-05-17T23:41:11+00:00 2026-05-17T23:41:11+00:00

I would like to select the value of the first href attribute from documents

0

I would like to select the value of the first “href” attribute from documents like this using XPath:

<div>
  <a href="#a">
    <span>foo</span>
  </a>

  <a href="#b">
    <span>bar</span>
  </a>

  <a href="#c">
    <span>baz</span>
  </a>
</div>

However, I am only interested in those a elements that govern spans with text content “bar” or “baz”. I was hoping that I could achieve that with the following Java code:

Document document = getDocument(); // returns non-null Document

XPath xpath = XPathFactory.newInstance().newXPath();
String href = xpath.evaluate("//a[fn:matches(span, '^ba.$')]/attribute::href", document);

but whenever I’m using one of the fn: functions in an XPathExpression, I get

javax.xml.transform.TransformerException: Unknown error in XPath.
    at com.sun.org.apache.xpath.internal.XPath.execute(XPath.java:363)
    at com.sun.org.apache.xpath.internal.XPath.execute(XPath.java:301)
    at com.sun.org.apache.xpath.internal.jaxp.XPathImpl.eval(XPathImpl.java:210)
    at com.sun.org.apache.xpath.internal.jaxp.XPathImpl.evaluate(XPathImpl.java:275)
    at com.sun.org.apache.xpath.internal.jaxp.XPathImpl.evaluate(XPathImpl.java:365)
    at MyCode(MyCode.java:71)
Caused by: java.lang.NullPointerException
    at com.sun.org.apache.xpath.internal.functions.FuncExtFunction.execute(FuncExtFunction.java:206)
    at com.sun.org.apache.xpath.internal.axes.PredicatedNodeTest.executePredicates(PredicatedNodeTest.java:340)
[...]

Similar Exceptions are thrown when I use fn:starts-with. I’m using JDK 1.6 on GNU/Linux.

Any ideas what I’m doing wrong? Thanks!