How to Read and Write XML Data in Java Using the DOM?

How to Access and Modify XML Data with Java

The Document Object Model (DOM) provides a standard interface for accessing and editing XML documents in Java. Here's a detailed guide on how to read and write XML files using DOM:

Reading XML Files:

1. Import Libraries: Begin by importing the necessary XML-related libraries:

   import javax.xml.parsers.*;
   import javax.xml.transform.*;
   import javax.xml.transform.dom.*;
   import javax.xml.transform.stream.*;
   import org.xml.sax.*;
   import org.w3c.dom.*;

2. Instantiate DocumentBuilderFactory: Create an instance of DocumentBuilderFactory, responsible for creating DocumentBuilder objects:

   DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();

3. Create DocumentBuilder: Use the factory to obtain a DocumentBuilder instance for parsing the XML document:

   DocumentBuilder db = dbf.newDocumentBuilder();

4. Parse XML Document: Invoke parse() on the builder to parse the XML file and create a DOM model of the document:

   Document dom = db.parse(xmlFile);

5. Access XML Elements: Utilize getElementsByTagName(tag) to retrieve nodes corresponding to the specified tag:

   NodeList nl = doc.getElementsByTagName(tag);

6. Extract Text Value: If the node has child nodes, use getFirstChild().getNodeValue() to retrieve the text value:

   String value = nl.item(0).getFirstChild().getNodeValue();

Writing XML Files:

1. Initialize Document: Create a new Document instance:

   Document dom = db.newDocument();

2. Create Root Element: Establish the root element of the XML document:

   Element rootElement = dom.createElement("rootElement");

3. Add Child Elements: Append child elements to the root element and provide their text content:

   Element childElement = dom.createElement("childElement");
   childElement.appendChild(dom.createTextNode("text content"));
   rootElement.appendChild(childElement);

4. Append Root Element to Document: Add the root element to the document:

   dom.appendChild(rootElement);

5. Instantiate Transformer: Create a Transformer instance for transforming the DOM model into an XML document:

   Transformer tr = TransformerFactory.newInstance().newTransformer();

6. Set Transformer Properties: Configure the transformer to indent the XML and use proper encoding:

   tr.setOutputProperty(OutputKeys.INDENT, "yes");
   tr.setOutputProperty(OutputKeys.METHOD, "xml");
   tr.setOutputProperty(OutputKeys.ENCODING, "UTF-8");

7. Transform and Save XML: Pass the DOM source to the transformer and specify the destination file for saving as XML:

   tr.transform(new DOMSource(dom), new StreamResult(new FileOutputStream(outputFile)));

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