Java HTML / XML How to - Use XPath to parse an XML file for attribute value

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Question

We would like to know how to use XPath to parse an XML file for attribute value.

Answer

import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.xpath.XPathConstants;
import javax.xml.xpath.XPathExpression;
import javax.xml.xpath.XPathFactory;
/* www .j  ava2  s. c o m*/
import org.w3c.dom.Document;

public class Main {

  private static final String CFG_FILE = "test.xml";
  private static final String XPATH_FOR_PRM_MaxThread = "/config/param[@id='MaxThread']/text()";

  public static void main(String[] args) throws Exception {
    DocumentBuilderFactory docFactory = DocumentBuilderFactory.newInstance();
    docFactory.setNamespaceAware(true);
    DocumentBuilder builder;
    builder = docFactory.newDocumentBuilder();
    Document doc = builder.parse(CFG_FILE);
    XPathExpression expr = XPathFactory.newInstance().newXPath()
        .compile(XPATH_FOR_PRM_MaxThread);
    Object result = expr.evaluate(doc, XPathConstants.NUMBER);
    if (result instanceof Double) {
      System.out.println(((Double) result).intValue());
    }

  }
}

test.xml

<?xml version="1.0" encoding="UTF-8"?>
<config>
    <param id="MaxThread" desc="MaxThread"        type="int">250</param>
    <param id="rTmo"      desc="RespTimeout (ms)" type="int">5000</param>
</config>

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