Question

I have an inventory record XML file to store the quantity of each item.

<Inventory>
<Item>
    <ManufacturerName>Brand1</ManufacturerName>
    <ProductType>TV</ProductType>
    <Quantity>146</Quantity>
</Item>
<Item>
    <ManufacturerName>Brand2</ManufacturerName>
    <ProductType>TV</ProductType>
    <Quantity>221</Quantity>
</Item>
<Item>
    <ManufacturerName>Brand3</ManufacturerName>
    <ProductType>TV</ProductType>
    <Quantity>36</Quantity>
</Item>
</Inventory>

In my java program, if I get a request for a certain item, I check the quantity of items of that type remaining (Quantity parameter) and, if there are enough, subtract that amount from the XML file. I can do this by looping through each node of the XML and checking the one I want, but I was hoping there was a faster way of accessing one particular node right away. Maybe the structure of the XML file can be changed to make it more accessible but I can’t think of one.

Answer 1

What you are looking for is XPath, here is a small sample:

import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.xpath.XPath;
import javax.xml.xpath.XPathConstants;
import javax.xml.xpath.XPathExpression;
import javax.xml.xpath.XPathFactory;

import org.w3c.dom.Document;
import org.w3c.dom.NodeList;

public class GetAllTheChildren {
    public static void main(String[] args) {
    
        try{
            DocumentBuilderFactory documentBuilderFactory = DocumentBuilderFactory.newInstance();
            documentBuilderFactory.setNamespaceAware(true);
            DocumentBuilder builder = documentBuilderFactory.newDocumentBuilder();
            Document doc = builder.parse("/home/eugen/Desktop/input.txt");
            
            XPathFactory xPathFactory = XPathFactory.newInstance();
            XPath xpath = xPathFactory.newXPath();
        
            XPathExpression expression = xpath.compile("/Inventory/Item[Quantity>200]/*");
        
            NodeList nodes = (NodeList) expression.evaluate(doc, XPathConstants.NODESET);
        
            for(int i = 0;i<nodes.getLength();i++){
                System.out.println(nodes.item(i).getNodeName());
                System.out.println(nodes.item(i).getTextContent());
            }
        } catch(Exception exception){
            exception.printStackTrace();
        }
    }
}

You probably need to play a bit more with it

Cheers, Eugene.