XML child node attribute value

Question

I'm trying to read xml file, ex :

<entry>
    <title>FEED TITLE</title>
    <id>5467sdad98787ad3149878sasda</id>
    <tempi type="application/xml">
      <conento xmlns="http://mydomainname.com/xsd/radiofeed.xsd" madeIn="USA" />
    </tempi>
</entry>

Here is the code I have so far :

Here is my attempt of trying to code this, what to say not successful thats why I started bounty. Here it is http://pastebin.com/huKP4KED .

Bounty update :

I really really tried to do this for days now didn't expect to be so hard, I'll accept useful links/books/tutorials but prefer code because I need this done yesterday.

Here is what I need:

Concerning xml above :

• I need to get value of title, id
• attribute value of tempi as well as madeIn attribute value of contento

What is the best way to do this ?

EDIT:

@Pascal Thivent

Maybe creating method would be good idea like public String getValue(String xml, Element elementname), where you specify tag name, the method returns tag value or tag attribute(maybe give it name as additional method argument) if the value is not available

What I really want to get certain tag value or attribute if tag value(s) is not available, so I'm in the process of thinking what is the best way to do so since I've never done it before

Answer 1

Use Element.getAttribute and Element.setAttribute

In your example, ((Node) content.item(0)).getFirstChild().getAttributes(). Assuming that content is a typo, and you mean contento, getFirstChild is correctly returning NULL as contento has no children. Try: ((Node) contento.item(0)).getAttributes() instead.

Another issue is that by using getFirstChild and getChildNodes()[0] without checking the return value, you are running the risk of picking up child text nodes, instead of the element you want.

Answer 2

As pointed out, <contento> doesn't have any child so instead of:

(contento.item(0)).getFirstChild().getAttributes()

You should treat the Node as Element and use getAttribute(String), something like this:

((Element)contento.item(0)).getAttribute("madeIn")

Here is a modified version of your code (it's not the most robust code I've written):

InputStream inputStream = new ByteArrayInputStream(xml.getBytes());
DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();
DocumentBuilder db = dbf.newDocumentBuilder();
Document doc = db.parse(inputStream);
doc.getDocumentElement().normalize();
System.out.println("Root element " + doc.getDocumentElement().getNodeName());
NodeList nodeLst = doc.getElementsByTagName("entry");
System.out.println("Information of all entries");

for (int s = 0; s < nodeLst.getLength(); s++) {

    Node fstNode = nodeLst.item(s);

    if (fstNode.getNodeType() == Node.ELEMENT_NODE) {

        Element fstElmnt = (Element) fstNode;

        NodeList title = fstElmnt.getElementsByTagName("title").item(0).getChildNodes();
        System.out.println("Title : " + (title.item(0)).getNodeValue());

        NodeList id = fstElmnt.getElementsByTagName("id").item(0).getChildNodes();
        System.out.println("Id: " + (id.item(0)).getNodeValue());

        Node tempiNode = fstElmnt.getElementsByTagName("tempi").item(0);
        System.out.println("Type : " + ((Element) tempiNode).getAttribute("type"));

        Node contento = tempiNode.getChildNodes().item(0);
        System.out.println("Made in : " + ((Element) contento).getAttribute("madeIn"));
    }
}

Running it on your XML snippet produces the following output:

Root element entry
Information of all entries
Title : FEED TITLE
Id: 5467sdad98787ad3149878sasda
Type : application/xml
Made in : USA

By the way, did you consider using something like Rome instead?

Answer 3

The best solution for this is to use XPath. Your pastebin is expired, but here's what I gathered. Let's say we have the following feed.xml file:

<?xml version="1.0" encoding="UTF-8" ?>
<entries>
<entry>
    <title>FEED TITLE 1</title>
    <id>id1</id>
    <tempi type="type1">
      <conento xmlns="dontcare?" madeIn="MadeIn1" />
    </tempi>
</entry>
<entry>
    <title>FEED TITLE 2</title>
    <id>id2</id>
    <tempi type="type2">
      <conento xmlns="dontcare?" madeIn="MadeIn2" />
    </tempi>
</entry>
<entry>
    <id>id3</id>
</entry>
</entries>

Here's a short but compile-and-runnable proof-of-concept (with feed.xml file in the same directory).

import javax.xml.xpath.*;
import javax.xml.parsers.*;
import org.w3c.dom.*;
import java.io.*;
import java.util.*;

public class XPathTest {
    static class Entry {
        final String title, id, origin, type;
        Entry(String title, String id, String origin, String type) {
            this.title = title;
            this.id = id;
            this.origin = origin;
            this.type = type;
        }
        @Override public String toString() {
            return String.format("%s:%s(%s)[%s]", id, title, origin, type);
        }
    }

    final static XPath xpath = XPathFactory.newInstance().newXPath();
    static String evalString(Node context, String path) throws XPathExpressionException {
        return (String) xpath.evaluate(path, context, XPathConstants.STRING);
    }

    public static void main(String[] args) throws Exception {
        File file = new File("feed.xml");
        Document document = DocumentBuilderFactory.newInstance().newDocumentBuilder().parse(file);
        NodeList entriesNodeList = (NodeList) xpath.evaluate("//entry", document, XPathConstants.NODESET);

        List<Entry> entries = new ArrayList<Entry>();
        for (int i = 0; i < entriesNodeList.getLength(); i++) {
            Node entryNode = entriesNodeList.item(i);
            entries.add(new Entry(
                evalString(entryNode, "title"),
                evalString(entryNode, "id"),
                evalString(entryNode, "tempi/conento/@madeIn"),
                evalString(entryNode, "tempi/@type")
            ));
        }
        for (Entry entry : entries) {
            System.out.println(entry);
        }
    }
}

This produces the following output:

id1:FEED TITLE 1(MadeIn1)[type1]
id2:FEED TITLE 2(MadeIn2)[type2]
id3:()[]

Note how using XPath makes the value retrieval very simple, intuitive, readable, and straightforward, and "missing" values are also gracefully handled.

API links

• package javax.xml.xpath
• http://www.w3.org/TR/xpath
• Wikipedia/XPath