XMLWriterDOM.java

package orderprocessing.service;

import java.io.File;
import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.transform.OutputKeys;
import javax.xml.transform.Transformer;
import javax.xml.transform.TransformerFactory;
import javax.xml.transform.dom.DOMSource;
import javax.xml.transform.stream.StreamResult;
import orderprocessing.data.Order;
import org.w3c.dom.Document;
import org.w3c.dom.Element;
import org.w3c.dom.Node;
 
 
public class XMLWriterDOM {
	
	private static XMLWriterDOM instance = null;
	private final String retrievePath;
	
	private XMLWriterDOM(){
		retrievePath="/path/to/orders.xml";
	}
	
	public static XMLWriterDOM getInstance() {
		if(instance == null){
			instance= new XMLWriterDOM();
		}
		return instance;
	}
	
	public void saveOrder(Order order){
		DocumentBuilderFactory dbFactory = DocumentBuilderFactory.newInstance();
        DocumentBuilder dBuilder;
        try {
            dBuilder = dbFactory.newDocumentBuilder();
           Document doc = dBuilder.parse(retrievePath);
           
            Element rootElement = doc.getDocumentElement();
 
            rootElement.appendChild(getOrder(order, doc));
 
            TransformerFactory transformerFactory = TransformerFactory.newInstance();
            Transformer transformer = transformerFactory.newTransformer();

            transformer.setOutputProperty(OutputKeys.INDENT, "yes");
            DOMSource source = new DOMSource(doc);
 
            StreamResult console = new StreamResult(System.out);
            StreamResult file = new StreamResult(new File(retrievePath));
 
            transformer.transform(source, console);
            transformer.transform(source, file);
            System.out.println("DONE");
 
        } catch (Exception e) {
            e.printStackTrace();
        }
	}
 
    
    private Node getOrder(Order order,Document doc){
    	Element orderElement = doc.createElement("Order");
    	
    	Element indexElement = doc.createElement("index");
    	indexElement.setTextContent(order.getIndex());
    	
    	Element priceElement = doc.createElement("price");
    	priceElement.setTextContent(Double.toString(order.getPrice()));
    	
    	orderElement.appendChild(indexElement);
    	orderElement.appendChild(priceElement);
    	
    	return orderElement;
    	
    }
 
}