In order to use dom4j and Xpath the first thing is download the jar file you need .

Dom4j code need two jar file .  1. [dom4j.jar](https://dom4j.github.io) 2. [jaxen.jar](https://sourceforge.net/projects/jaxen/)

Click and download the jar file , add it to your project .
Next is one of my project , you can see my jar file.

One of the first things you'll probably want to do is to parse an XML document of some kind. This is easy to do in dom4j. The following code demonstrates how to this.
   
code: ``` import java.net.URL;

public Document parse(URL url) throws DocumentException {
    SAXReader reader = new SAXReader();
    Document document = reader.read(url);
    return document;
} } ```

From the code , my can know that dom4j read xml by using SAXReader() , except this , we also know it can read url .

public void bar(Document document) throws DocumentException {

        Element root = document.getRootElement();

        // iterate through child elements of root
        for ( Iterator i = root.elementIterator(); i.hasNext(); ) {
            Element element = (Element) i.next();
            // do something
        }

        // iterate through child elements of root with element name "foo"
        for ( Iterator i = root.elementIterator( "foo" ); i.hasNext(); ) {
            Element foo = (Element) i.next();
            // do something
        }

        // iterate through attributes of root 
        for ( Iterator i = root.attributeIterator(); i.hasNext(); ) {
            Attribute attribute = (Attribute) i.next();
            // do something
        }
     }

public void bar(Document document) {
        List list = document.selectNodes( "//foo/bar" );

        Node node = document.selectSingleNode( "//foo/bar/author" );

        String name = node.valueOf( "@name" );
    }

public void findLinks(Document document) throws DocumentException {

        List list = document.selectNodes( "//a/@href" );

        for (Iterator iter = list.iterator(); iter.hasNext(); ) {
            Attribute attribute = (Attribute) iter.next();
            String url = attribute.getValue();
        }
    }

public void treeWalk(Document document) {
        treeWalk( document.getRootElement() );
    }

    public void treeWalk(Element element) {
        for ( int i = 0, size = element.nodeCount(); i < size; i++ ) {
            Node node = element.node(i);
            if ( node instanceof Element ) {
                treeWalk( (Element) node );
            }
            else {
                // do something....
            }
        }
    }

But I don't recommend you use this code to walk the xml tree , I'd like to use the code next .

    public static Element getRootElement(Document doc){//get root of the xml tree.
        return doc.getRootElement();
    }

    public static void treeWalk(Element element){//start recursion.
        for (Iterator i = element.elementIterator(); i.hasNext(); ){
            Element p = (Element) i.next();

            if (p.hasMixedContent()){
                Attribute attribute = p.attribute("name");//take the "name" Attribute.
                if (attribute!=null) {
                    System.out.println(attribute.getName() + ":" + attribute.getValue());
                }
                System.out.println(p.getName()+":path is "+p.getPath());
                treeWalk(p);//start the recursion.
            }else{
                System.out.println("test.xml last node: "+p.getPath()+" "+p.getText());

            }
        }
    }

import org.dom4j.Document;
import org.dom4j.DocumentHelper;
import org.dom4j.Element;

public class Foo {

    public Document createDocument() {
        Document document = DocumentHelper.createDocument();
        Element root = document.addElement( "root" );

        Element author1 = root.addElement( "author" )
            .addAttribute( "name", "James" )
            .addAttribute( "location", "UK" )
            .addText( "James Strachan" );
        
        Element author2 = root.addElement( "author" )
            .addAttribute( "name", "Bob" )
            .addAttribute( "location", "US" )
            .addText( "Bob McWhirter" );

        return document;
    }
}

public static void findInfobox(Document document) {

        Element rootElement = document.getRootElement();

        String outpath = "/Volumes/Slow Disk/GraduatonData/GraduationDataCSV/test.csv";

        CsvWriter writer = new CsvWriter(outpath, ',', Charset.forName("Utf8"));

        for (Iterator i = rootElement.elementIterator();i.hasNext();){

            Element p = (Element) i.next();

            String mainNodeName = p.valueOf("./@name");

            List<Node> inbox = p.selectNodes("./infobox/item");//this is right code.

            for (Iterator item = inbox.iterator();item.hasNext();){

                Element itemElement =(Element) item.next();

                //String rdf = mainNodeName;

                //writer.write(mainNodeName);

                //List<String> rdftemp;

                String[] rdftemp = new String[3];

                rdftemp[0] = mainNodeName;
                for (Iterator i1 = itemElement.elementIterator();i1.hasNext();){

                    Element p1 = (Element) i1.next();

                    if (p1.getName().equals("name")){
                        rdftemp[2] = p1.getText();
                        //rdf+=p1.getText()+",";

                        //writer.write(p1.getText());
                    }

                    if (p1.getName().equals("value")){
                        rdftemp[1] = p1.getText();
                        //rdf+=p1.getText()+")";

                        //writer.write(p1.getText());
                    }

                }

                //rdf p1 = new rdf(rdf);



                try {
                    rdfList.add(new rdf(rdftemp));
                    writer.writeRecord(rdftemp);
                }
                catch (Exception e){
                    System.out.println(e.getMessage());
                }

                //writer.writeRecord(rdf);
                //System.out.println(rdf);
            }
        }
    }

Just as you see , I used Xpath to select the node I want , which is convenient .

Next figure show my xml file tree which I use my code on it.