Read data from an xml file and process it with Java.

XML is a data format very flexible and widely used. With Java is very simple to read data from an xml source and process them or print them.

Suppose you have a file like this:

Code:

<?xml version="1.0" ?>
<?xml-stylesheet type="text/xsl" href="books.xsl" ?>
<books>
	<book>
		<title>Programming in XML</title>
		<author>Marc Vince</author>
		<pages>348</pages>
		<category>Programming</category>
	</book>
	<book>
		<title>Programming in C#</title>
		<author>Loren Gallipyos</author>
		<pages>234</pages>
		<category>Programming</category>
	</book>
	<book>
		<title>Android</title>
		<author>Norman Bert</author>
		<pages>419</pages>
		<category>Operating Systems</category>
	</book>
	<book>
		<title>Linux</title>
		<author>Hurth Francy</author>
		<pages>294</pages>
		<category>Operating Systems</category>
	</book>
	<book>
		<title>WordPress</title>
		<author>Milena Zarch</author>
		<pages>364</pages>
		<category>CMS</category>
	</book>
	<book>
		<title>Joomla!</title>
		<author>Denise Patrics</author>
		<pages>163</pages>
		<category>CMS</category>
	</book>
	<book>
		<title>jQuery</title>
		<author>Teresa Curtis</author>
		<pages>349</pages>
		<category>Programming</category>
	</book>
</books>

The example shows how to read the file and print the data on screen:

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 xmlFile = new File("books.xml");
			DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();
			DocumentBuilder db = dbf.newDocumentBuilder();
			Document doc = db.parse(xmlFile);
			doc.getDocumentElement().normalize();

			System.out.println("List of the books" );
			NodeList nl = doc.getElementsByTagName("book");
			System.out.println("------------------------------------");

				for (int n = 0; n < nl.getLength(); n++) {
					Node node = nl.item(n);
					if (node.getNodeType() == Node.ELEMENT_NODE) {
						Element e = (Element) node;
						System.out.println();
						System.out.println("Title : "  + getTagValue("title",e));
						System.out.println("Author : "  + getTagValue("author",e));
						System.out.println("Pages : "  + getTagValue("pages",e));
						System.out.println("Category : "  + getTagValue("category",e));
					}
				}
			} catch (Exception e) {
				e.printStackTrace();
		}
	}
 
	private static String getTagValue(String sTag, Element e)
	{
	NodeList nlList= e.getElementsByTagName(sTag).item(0).getChildNodes();
	Node nValue = (Node) nlList.item(0); 
	return nValue.getNodeValue();
	}
}

Result:

>java -cp . ReadXMLFile
List of the books
------------------------------------

Title : Programming in XML
Author : Marc Vince
Pages : 348
Category : Programming

Title : Programming in C#
Author : Loren Gallipyos
Pages : 234
Category : Programming

Title : Android
Author : Norman Bert
Pages : 419
Category : Operating Systems

Title : Linux
Author : Hurth Francy
Pages : 294
Category : Operating Systems

Title : WordPress
Author : Milena Zarch
Pages : 364
Category : CMS

Title : Joomla!
Author : Denise Patrics
Pages : 163
Category : CMS

Title : jQuery
Author : Teresa Curtis
Pages : 349
Category : Programming
>Exit code: 0