Sample xPaths: http://stackoverflow.com/questions/39457005/returning-empty-string-when-attribute-does-not-match-return-text-when-attribute

SaxonXPathGist.java

package com.proquest.xslt;

import java.io.StringReader;
import java.util.Iterator;

import javax.xml.transform.stream.StreamSource;

import net.sf.saxon.s9api.DocumentBuilder;
import net.sf.saxon.s9api.Processor;
import net.sf.saxon.s9api.SaxonApiException;
import net.sf.saxon.s9api.XPathCompiler;
import net.sf.saxon.s9api.XPathExecutable;
import net.sf.saxon.s9api.XPathSelector;
import net.sf.saxon.s9api.XdmItem;
import net.sf.saxon.s9api.XdmNode;

/**
 * Created by BDF on 9/13/16.
 *
 * @author BDF
 */
public class SaxonXPathGist {


	public static void main(String [] args) throws SaxonApiException {
		String xPath1 = "for $a in /test " +
				"    return " +
				"        (if ($a/value[@cat=\"mythology\"]) then " +
				"            $a/value[@cat=\"mythology\"] else " +
				"            \"\")";

		String xPath2 = "for $a in /test/value " +
				" return " +
				"    if ($a[@cat='mythology']) then " +
				"  $a[@cat='mythology'] else " +
				"\"\"";

		String xml = "<test>\n" +
				"    <value cat=\"fiction\">At the edge of the orchard</value>\n" +
				"    <value cat=\"mythology\">Hero with a thousand faces</value>\n" +
				"    <value cat=\"fiction\">Spill simmer falter wither</value>\n" +
				"</test>";

		Processor proc = new Processor(true);
		XPathCompiler xPathCompiler = proc.newXPathCompiler();
		xPathCompiler.setLanguageVersion("3.1");

		DocumentBuilder docBuilder = proc.newDocumentBuilder();
		XdmNode xdmNode = docBuilder.build(new StreamSource(new StringReader(xml)));
		printResults(xPath1, xPathCompiler, xdmNode);
		printResults(xPath2, xPathCompiler, xdmNode);
	}

	private static void printResults(String xPath1, XPathCompiler xPathCompiler, XdmNode xdmNode) throws SaxonApiException {
		XPathExecutable xPathExe = xPathCompiler.compile(xPath1);
		final XPathSelector selector = xPathExe.load();
		selector.setContextItem(xdmNode);
		Iterator<XdmItem> iter = selector.iterator();
		while (iter.hasNext()) {
			System.out.println(String.format("'%s'", iter.next().getStringValue()));
		}
		System.out.println();
	}
}