Extracting data by tag name from xml object

Question

Im trying to extract data from a database using xml tags but I keeping getting this error

'java.lang.String org.w3c.dom.Node.getNodeValue()' on a null object reference

Not sure why its saying the tag is null when I have a log of the string before I try to extracts the data and it looks like it should I believe.

<?xml version="1.0" ?>
  <database>
    <account>
     <id>1</id>
     <fname>john</fname>
     <lname>smith</lname>
     <status>1</status>
   </account>
 </database>

That is the output from the string which I'm trying to extract the data from and here is the code I'm using to extract it.

        DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();;
        DocumentBuilder db = dbf.newDocumentBuilder();
        Document dom = db.parse (new ByteArrayInputStream(s.getBytes()));
        Element docEle = dom.getDocumentElement ();

        NodeList nl = docEle.getElementsByTagName("account");

        Element entry = (Element)nl.item(0);
        Element id = (Element)entry.getElementsByTagName("id").item(0);
        Element fname= (Element)entry.getElementsByTagName("fname").item(0);
        Element lname = (Element)entry.getElementsByTagName("lname").item(0);
        Element status= (Element)entry.getElementsByTagName("status").item(0);

        user_id = id.getFirstChild().getNodeValue();
        user_fname = fname.getFirstChild().getNodeValue();
        user_lname = lname.getFirstChild().getNodeValue();
        user_status = status.getFirstChild().getNodeValue();

The app crashes when it try's to get the node value from the first element, any help Is appreciated and thanks in advance

The code above is very likely subtly wrong. If the default `file.encoding` is not UTF-8 (on Windows, it's Cp1252), `s.getBytes()` will return an array of Windows-1252 data, but since the XML doesn't declare an encoding it will default to UTF-8. Any characters above code point 127 will either be garbled, or the parse will fail. Never call the overload of `getBytes()` that doesn't take a `Charset`. Use `s.getBytes(StandardCharsets.UTF_8)`. — David Conrad, Feb 12 '17 at 14:26
Hi, I added the code you suggested but the app is still crashing, the server I am connecting to linux based if that makes a difference. — Andrew Dean, Feb 12 '17 at 14:33
Which one comes up `null`? Possible duplicate of [What is a NullPointerException and how do I fix it?](http://stackoverflow.com/questions/218384/what-is-a-nullpointerexception-and-how-do-i-fix-it) — David Conrad, Feb 12 '17 at 14:42
You should learn [How to debug small programs](https://ericlippert.com/2014/03/05/how-to-debug-small-programs/). It is much more effective than asking here. — Thomas Fritsch, Feb 12 '17 at 15:08

score 0 · Answer 1 · answered Feb 12 '17 at 13:55

0

You have started the <account> tag but did not end it. Change </user> to </account>

answered Feb 12 '17 at 13:55

Rishav Sengupta

241
2
4

I did correct that mistake but it made no difference – Andrew Dean Feb 12 '17 at 14:26
1

@AndrewDean Your code doesn't even compile. There are no `radius` and `loc` variables. Post your real code if you want real help. – David Conrad Feb 12 '17 at 14:28
@DavidConrad my apologises I changed some of the variable names as its part of assignment but have corrected them on the post. – Andrew Dean Feb 12 '17 at 14:38

score 0 · Accepted Answer · answered Feb 12 '17 at 15:08

Managed to figure it out, and this would be helpful for anyone with similar issues i hope.

to be able to read the tag names from an xml string I did the following (s is the xml string variable)

            InputSource is = new InputSource();
            is.setCharacterStream(new StringReader(s));

            DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();;
            DocumentBuilder db = dbf.newDocumentBuilder();
            Document dom = db.parse(is);
            Element docEle = dom.getDocumentElement ();

            NodeList nl = docEle.getChildNodes();

            if (nl != null) {
                int length = nl.getLength();
                for (int i = 0; i < length; i++) {
                    if (nl.item(i).getNodeType() == Node.ELEMENT_NODE) {
                        Element el = (Element) nl.item(i);
                        if (el.getNodeName().contains("account")) {
                            user_id = el.getElementsByTagName("id").item(0).getTextContent();
                            user_fname = el.getElementsByTagName("fname").item(0).getTextContent();
                            user_lname = el.getElementsByTagName("lname").item(0).getTextContent();
                            user_status = el.getElementsByTagName("status").item(0).getTextContent();
                        }
                    }
                }
            }

the user_ variables have the xml tag values

Extracting data by tag name from xml object

2 Answers2