Java-XML in 3 minutes

XML is a clear and concise way to describe data.

Let’s see an example:

<?xml version="1.0" encoding="UTF-8"?>
<message id="123">
    <from>Nikos</from>
    <to>Sofia</to>
    <text>Hello from XML!</text>
</message>

This simple document represents a “message”.

<message>
    ...
</message>

The message has an attribute called @id.

<message id="...">
    ...
</message>

It has also three children.

<from> ... </from>
<to> ... </to>
<text> ... </text>

Step 1. Download dom4j

To download dom4j go to dom4j.org → Download → Download the current release SourceForge → dom4j-1.6.1.jar

Note:

If you are using Java 1.5 download dom4j-1.5.2.jar, and
If you are using Java 1.4 download dom4j-1.4.zip; it has a dom4j-full.jar inside.

Step 2. Place the jar in the classpath

In Eclipse: Project → Java Build Path → Libraries → Add External JARs…

In Netbeans: File → ”Project” Properties → Libraries → Add JAR/Folder

In JDeveloper 11g: Tools → Project Properties… → Libraries and Classpath → Add JAR/Directory…

Step 3. Create the XML document

	// Create the document
	Document document = DocumentHelper.createDocument();
	// Add the root
	Element root = document.addElement("message").addAttribute("id", "123");
	// Add the "from" element
	root.addElement("from").addText("Nikos");
	// Add the "to" element
	root.addElement("to").addText("Sofia");
	// Add the "text" element
	root.addElement("text").addText("Hello from XML!");

That’s all!

Step 4. Save the XML document

// Make a pretty output
		OutputFormat format = OutputFormat.createPrettyPrint();
		format.setEncoding("UTF-8");
		format.setTrimText(false);
// Save it
		XMLWriter writer = new XMLWriter(new FileWriter("C:/message.xml"), format);
		writer.write(document);
		writer.close();

Step 5. Read the XML document

// Locate the file
URL url = new File("C:/message.xml").toURI().toURL();
// Parse the document
Document document = new SAXReader().read(url);

Step 6. Get the information

// Get the root element
Element root = document.getRootElement();
// Get the id attribute
root.attributeValue("id");
// Get the from element
Element from = root.element("from");
if (from != null) {
   from.getText();
}

Step 7. Use some XPATH

// Get the root element
Element root = document.getRootElement();
// Get the id attribute
root.valueOf("@id");
// Get the from element
Node from = root.selectSingleNode("./from");
if (from != null) {
   from.getText();
}

A good XML tutorial can be found at w3schools.com.

Thank you.

Tags: dom4j, Java, XML