How to read XML file in Java using DOM parser?

Use the DOM parser to read XML files, first create DocumentBuilderFactory and DocumentBuilder, parse XML into Document object, call normalize() to normalize the structure, and then get the node list through getElementsByTagName() and traverse the data to extract. At the same time, try-catch needs to be used to handle ParserConfigurationException, SAXException and IOException exceptions.

To read an XML file in Java using the DOM parser, you use the built-in Document Object Model (DOM) API provided by Java's javax.xml.parsers package. The DOM parser loads the entire XML document into memory as a tree structure, allowing easy traversal and manipulation.

1. Set Up the DOM Parser

Use DocumentBuilderFactory and DocumentBuilder to parse the XML file into a Document object.

Example:

 DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();
DocumentBuilder builder = factory.newDocumentBuilder();
Document document = builder.parse(new File("input.xml"));

2. Normalize the XML Structure

Call document.getDocumentElement().normalize() to ensure the root element is properly set and whitespace is handled consistently.

This step helps avoid issues when accessing child elements.

Example:

 document.getDocumentElement().normalize();

3. Access Elements by Tag Name

Use getElementsByTagName() to retrieve a list of nodes matching a tag name.

Example: Reading all <student> elements

 NodeList nodeList = document.getElementsByTagName("student");

for (int i = 0; i < nodeList.getLength(); i ) {
    Node node = nodeList.item(i);
    
    if (node.getNodeType() == Node.ELEMENT_NODE) ​​{
        Element element = (Element) node;
        String id = element.getAttribute("id");
        String name = element.getElementsByTagName("name").item(0).getTextContent();
        String grade = element.getElementsByTagName("grade").item(0).getTextContent();
        
        System.out.println("ID: " id ", Name: " name ", Grade: " grade);
    }
}

4. Handle Exceptions

Always wrap your code in a try-catch block to handle possible exceptions like ParserConfigurationException , SAXException , or IOException .

Example:

 try {
    // parsing code here
} catch (ParserConfigurationException | SAXException | IOException e) {
    e.printStackTrace();
}

Reading XML with DOM is straightforward for small to medium files. It gives full control over the document but uses more memory since the whole file is loaded at once. Basically that's all you need to get started.

The above is the detailed content of How to read XML file in Java using DOM parser?. For more information, please follow other related articles on the PHP Chinese website!