How to build an XML document tree with the DOM API?

If you want to build an XML document tree with the DOM (Document Object Model) API, you can follow these suggestions:

1. Use the factory class to create DocumentBuilder object:

      DocumentBuilderFactory f = DocumentBuilderFactory.newInstance();
      DocumentBuilder b = f.newDocumentBuilder();

2. Call the newDocument() method on the DocumentBuilder object to create a new Document object:

      Document d = b.newDocument();
      System.out.println("Implementation class:\n   "+d.getClass().getName());

3. Call the createElement() method on the Document object to create a new Element object. Then add it to the Document as the root element:

      Element e = d.createElement("User"); 
      d.appendChild(e);

3. Call the createElement() method on the Document object repeatedly to create new Element objects. Then add them to parent elements to build the XML document tree:

	  Element c = d.createElement("ID");
	  c.appendChild(d.createTextNode("202"));
	  e.appendChild(c);

Here is a complete example of parsing an XML file with DOM API, DomXmlParser.java:

// Copyright (c) 2017 FYIcenter.com
import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.parsers.DocumentBuilder;
import org.w3c.dom.Document;
import org.w3c.dom.Element;
import org.w3c.dom.Text;
import org.w3c.dom.Node;
import org.w3c.dom.NodeList;

public class DomDocumentTree {
   static String dot = "............................................................";
   public static void main(String[] args) throws Exception {
      DocumentBuilderFactory f = DocumentBuilderFactory.newInstance();
      DocumentBuilder b = f.newDocumentBuilder();
      Document d = b.newDocument();
      System.out.println("Implementation class:\n   "+d.getClass().getName());

      Element e = d.createElement("User"); 
      d.appendChild(e);
	  
	  Element c = d.createElement("ID");
	  c.appendChild(d.createTextNode("202"));
	  e.appendChild(c);

	  c = d.createElement("Name");
	  c.appendChild(d.createTextNode("Frank Y. Ivy"));
	  e.appendChild(c);

	  c = d.createElement("BirthDate");
	  c.appendChild(d.createTextNode("1970-01-01"));
	  e.appendChild(c);
	  
      System.out.println("DOM object elements and text contents:");
	  Node n = d.getDocumentElement();
	  printText(n, 1);
   }
   
   public static void printText(Node n, int l) {
      String v = "";
      if (n.getNodeType()==Node.TEXT_NODE) v = n.getTextContent();
      System.out.println(dot.substring(0,l)+n.getNodeName()+":"+v);
	  NodeList c = n.getChildNodes();
	  for (int i=0; i<c.getLength(); i++) {
	     printText(c.item(i),l+1);
	  }
   }
}

Compile and run the example program, DomDocumentTree.java:

>\fyicenter\jdk-1.8.0\bin\javac DomDocumentTree.java

>\fyicenter\jdk-1.8.0\bin\java DomDocumentTree

Implementation class:
   com.sun.org.apache.xerces.internal.dom.DocumentImpl
   
DOM object elements and text contents:
.User:
..ID:
...#text:202
..Name:
...#text:Frank Y. Ivy
..BirthDate:
...#text:1970-01-01

⇒Using XML DOM API with Apache Xerces

⇒⇒FAQ for Apache Xerces XML Parser