Count the no of a particular element in xml file

[pramod talekar]

Hi,

Could anyone please tell me how to count the number of a particular tag in xml

e.g. a file contains <abc> tag 2 times , then is there a function to count it's no. of occurances ?


Please advise.

[Paul Clapham]

You could load the file into a Document, then use getElementsByTagName("abc") to return a list of those elements.

[g tsuji]

I would say, even though it is not as radically different of how to count the number of dust particles in a clean room from how to count the number of a molecule in a molar volumn or from the number of cards in a dealing shoe, the way of counting the number of tag abc is still... different for different operation context. What then is the context?

[H Paul]

The idea is to use xpath count function

1. count(//help)
This is NO xml namespace. This is OK by the method useInputSource(). The count is 1 as expected.

2. count(//mylaws:help)
This is with xml namespace. This is NOT OK by the method useDom() and selectCount(Object inputSource, String expression) { // This is for useDom()
The count is 0.

I tested with XPath-View and it return 1 as expected.

What/where/why is the issue in the method selectCount(Object inputSource, String expression) { // This is for useDom()

public class XPathTool {

	/**
	 * @param args
	 */
	public static void main(String[] args) {
		// TODO Auto-generated method stub

		useDom(); // with xml namespace
		useInputSource(); // without xml namespace
	}
	
	private static void useDom() {
		// TODO Auto-generated method stub

		InputSource inputSource = new InputSource(
				new StringReader(
						"<mylaws:law xmlns:mylaws=\"http://www.mylaws.org\"><mylaws:help>to help to is to helped</mylaws:help></mylaws:law>"));

		DocumentBuilderFactory documentBuilderFactory = DocumentBuilderFactory
				.newInstance();
documentBuilderFactory.setNamespaceAware(true);  // Added this missing code as suggested by g tsuji and it works. Thanks
		DocumentBuilder documentBuilder;
		try {
			documentBuilder = documentBuilderFactory.newDocumentBuilder();
			Document document = documentBuilder.parse(inputSource);
			String expression = "count(//mylaws:help)";
			int count= selectCount(document, expression);
			System.out.println(count);
			display(document);
		} catch (ParserConfigurationException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		} catch (SAXException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		} catch (IOException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}

	}



	public static int selectCount(Object inputSource, String expression) {  // This is for useDom()
		XPathFactory xPathFactory = XPathFactory.newInstance();
		XPath xPath = xPathFactory.newXPath();
		xPath.setNamespaceContext(new NamespaceContext() {
			@Override
			public String getNamespaceURI(String prefix) {
				if ("mylaws".equals(prefix))
					return "http://www.mylaws.org";
				return null;
			}

			@Override
			public String getPrefix(String namespaceURI) {
				// TODO Auto-generated method stub
				if ("http://www.mylaws.org".equals(namespaceURI))
					return "mylaws";
				return null;
			}

			@Override
			public Iterator getPrefixes(String namespaceURI) {
				// TODO Auto-generated method stub
				return null;
			}
		});
		int count = 0;
		try {
			XPathExpression xPathExpression = xPath.compile(expression);
			count = Integer.parseInt(xPathExpression.evaluate(inputSource));
		} catch (XPathExpressionException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}

		return count;

	}

	private static void useInputSource() {
		// TODO Auto-generated method stub
		InputSource inputSource = new InputSource(new StringReader(
				"<law><help>to help to is to helped</help></law>"));
		String expression = "count(//help)";
		int count= selectCount(inputSource, expression);
		System.out.println(count);
	}
	
	public static int selectCount(InputSource inputSource, String expression) {  // This is for useInputSource()
		XPathFactory xPathFactory = XPathFactory.newInstance();
		XPath xPath = xPathFactory.newXPath();
		int count = 0;
		try {
			XPathExpression xPathExpression = xPath.compile(expression);
			count = Integer.parseInt(xPathExpression.evaluate(inputSource));
		} catch (XPathExpressionException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}

		return count;

	}

	
	public static void display(Document document) {
		TransformerFactory transformerFactory = TransformerFactory
				.newInstance();
		try {
			Transformer transformer = transformerFactory.newTransformer();

			transformer.transform(new DOMSource(document), new StreamResult(
					System.out));
		} catch (TransformerConfigurationException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		} catch (TransformerException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
	}
}

[g tsuji]

        DocumentBuilderFactory documentBuilderFactory = DocumentBuilderFactory   
                .newInstance();   
        documentBuilderFactory.setNamespaceAware(true);
        DocumentBuilder documentBuilder;

Maybe you should open your own thread for your own problem.

[H Paul]

1. Missing code added and works.

2. In which scenario (XML Input), the following method will be called

            public Iterator getPrefixes(String namespaceURI) {   
                // TODO Auto-generated method stub   
                return null;   
            }   

[pramod talekar]

Hi All,

At least for my problem, I just made some changes in the java class which was generating my xml so that xml won't have the same data twice.
Why I needed the count function is that I wanted to check if there was any duplicate data in the xml.

Thank you all for your advise.