import org.jdom2.Attribute;
import org.jdom2.Document;
import org.jdom2.Element;
import org.jdom2.JDOMException;
import org.jdom2.input.SAXBuilder;
import org.jdom2.output.Format;
import org.jdom2.output.XMLOutputter;

import java.io.File;
import java.io.FileInputStream;
import java.io.FileWriter;
import java.io.IOException;

public class WriteXml2 {
    public static void Writer() throws JDOMException, IOException {

        Document document = null;
        Element root = null;

        File xmlFile = new File("test.xml");
        if(xmlFile.exists()) {
            // try to load document from xml file if it exist
            // create a file input stream
            FileInputStream fis = new FileInputStream(xmlFile);
            // create a sax builder to parse the document
            SAXBuilder sb = new SAXBuilder();
            // parse the xml content provided by the file input stream and create a Document object
            document = sb.build(fis);
            // get the root element of the document
            root = document.getRootElement();
            fis.close();
        } else {
            // if it does not exist create a new document and new root
            document = new Document();
            root = new Element("productlist");
        }

        String nom = "linux";
        String ref = "F598";
        String date_deb = "20 jan 2020";
        String date_fin = "20 sep 2020";
        String nb_heurs = "350";
        String ens = "salouha";
        Element child = new Element("Formation");
        child.setAttribute(new Attribute("ref", ref));
        child.addContent(new Element("nom").setText(nom));
        child.addContent(new Element("date_deb").setText(date_deb));
        child.addContent(new Element("date_fin").setText(date_fin));
        child.addContent(new Element("nb_heurs").setText(nb_heurs));

        root.addContent(child);
        document.setContent(root);
        try {
            FileWriter writer = new FileWriter("test.xml");
            XMLOutputter outputter = new XMLOutputter();
            outputter.setFormat(Format.getPrettyFormat());
            outputter.output(document, writer);
            outputter.output(document, System.out);
            writer.close(); // close writer
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}