What is the best/simplest way to read in an XML file in Java application? [closed]

Currently our Java application uses the values held within a tab delimited *.cfg file. We need to change this application so that it now uses an XML file.

What is the best/simplest library to use in order to read in values from this file?

There are of course a lot of good solutions based on what you need. If it is just configuration, you should have a look at Jakarta commons-configuration and commons-digester.

You could always use the standard JDK method of getting a document :

import java.io.File;
import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
import org.w3c.dom.Document;

[...]

File file = new File("some/path");
DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();
DocumentBuilder db = dbf.newDocumentBuilder();
Document document = db.parse(file);

XML Code:

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

Java Code:

import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.parsers.DocumentBuilder;
import org.w3c.dom.Document;
import org.w3c.dom.NodeList;
import org.w3c.dom.Node;
import org.w3c.dom.Element;
import java.io.File;

public class ReadXMLFile {

  public static void main(String argv[]) {
    try {
    File fXmlFile = new File("/Users/mkyong/staff.xml");
    DocumentBuilderFactory dbFactory = DocumentBuilderFactory.newInstance();
    DocumentBuilder dBuilder = dbFactory.newDocumentBuilder();
    Document doc = dBuilder.parse(fXmlFile);
    doc.getDocumentElement().normalize();

    System.out.println("Root element :" + doc.getDocumentElement().getNodeName());
    NodeList nList = doc.getElementsByTagName("staff");
    System.out.println("----------------------------");

    for (int temp = 0; temp < nList.getLength(); temp++) {
        Node nNode = nList.item(temp);
        System.out.println("\nCurrent Element :" + nNode.getNodeName());
        if (nNode.getNodeType() == Node.ELEMENT_NODE) {
            Element eElement = (Element) nNode;
            System.out.println("Staff id : "
                               + eElement.getAttribute("id"));
            System.out.println("First Name : "
                               + eElement.getElementsByTagName("firstname")
                                 .item(0).getTextContent());
            System.out.println("Last Name : "
                               + eElement.getElementsByTagName("lastname")
                                 .item(0).getTextContent());
            System.out.println("Nick Name : "
                               + eElement.getElementsByTagName("nickname")
                                 .item(0).getTextContent());
            System.out.println("Salary : "
                               + eElement.getElementsByTagName("salary")
                                 .item(0).getTextContent());
        }
    }
    } catch (Exception e) {
    e.printStackTrace();
    }
  }
}

Output:

----------------

Root element :company
----------------------------

Current Element :staff
Staff id : 1001
First Name : yong
Last Name : mook kim
Nick Name : mkyong
Salary : 100000

Current Element :staff
Staff id : 2001
First Name : low
Last Name : yin fong
Nick Name : fong fong
Salary : 200000

I recommended you reading this: Normalization in DOM parsing with java - how does it work?

Example source.