java.lang.ClassCastException, DeepNodeListImpl cannot be cast

Question

here is my code :

 public void Login() {  
    try{
        DocumentBuilderFactory builderfactory = DocumentBuilderFactory.newInstance();
        DocumentBuilder db = builderfactory.newDocumentBuilder();

        File path = new File("src/dataPengguna/dataPengguna.xml");

        Document doc = db.parse(path);

        Element pengguna = (Element) doc.getElementsByTagName("pengguna");

        NodeList list = pengguna.getElementsByTagName("user");

        for (int i = 0; i < list.getLength(); i++) {
            Element user =  (Element) list.item(i);
            Node username =   user.getElementsByTagName("username").item(i);
            Node password =   user.getElementsByTagName("password").item(i);

            if(loginuser.getText().equals(username.getTextContent()) 
               && loginpass.getText().equals(password.getTextContent())){ 
                JOptionPane.showMessageDialog(rootPane, "welcome");
            }
        }
    }catch(Exception e){
      e.printStackTrace();

    }
    }

here is my xml :

     <?xml version="1.0" encoding="UTF-8"?>
     <pengguna>

         <user>
         <nama>septian</nama>
         <username>septiansykes</username>
         <password>1234</password>
         <status>belumpinjam</status> 
         </user>    

         <user>
         <nama>koko</nama>
         <username>kokosan</username>
         <password>12er</password>
         <status>belumpinjam</status> 
         </user>

         <user>
         <nama>tamrin</nama>
         <username>tamrincs</username>
         <password>gt234</password>
         <status>belumpinjam</status> 
         </user>

    </pengguna>

and here is my error :

  java.lang.ClassCastException:com.sun.org.apache.xerces.internal.dom.DeepNodeListImpl cannot be cast to org.w3c.dom.Element

i try to get the element at the xml file, i want to check the element username and password, but there is an error about the cast class, it's seem difficult for me,... thanks before

Answer 1

This is the problem:

Element pengguna = (Element) doc.getElementsByTagName("pengguna");

getElementsByTagName doesn't return a single element - it returns multiple elements. You probably want something like:

NodeList penggunas = doc.getElementsByTagName("pengguna");
if (penggunas.getLength() != 1) {
    // Handle this - e.g. throw an exception
}
Element pengguna = (Element) penggunas.item(0);

EDIT: Later, you've got a bug here:

Node username =   user.getElementsByTagName("username").item(i);
Node password =   user.getElementsByTagName("password").item(i);

This should be:

Node username =   user.getElementsByTagName("username").item(0);
Node password =   user.getElementsByTagName("password").item(0);

You're already within the user element - so you always want the first username and password elements within that element. Otherwise you're asking for the second username element within the second user element, the third username element within the third user element etc. The numbering is relevant to the element that you're in, not some global count.

Answer 2

getElementByTagName() returns a NodeList and you try to cast it to an Element . This line is incorrect and will give you the ClassCastException :

Element pengguna = (Element) doc.getElementsByTagName("pengguna");