Java Tutorial/XML/Comment

Add a comment at the beginning of the document

import java.io.File;
import javax.xml.parsers.DocumentBuilderFactory;
import org.w3c.dom.rument;
import org.w3c.dom.Document;
import org.w3c.dom.Element;
import org.w3c.dom.NodeList;
public class Main {
  public static void main(String[] argv) throws Exception {
    DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();
    factory.setValidating(true);
    factory.setExpandEntityReferences(false);
    Document doc = factory.newDocumentBuilder().parse(new File("filename"));
    Element element = doc.getDocumentElement();
    Comment comment = doc.createComment("A Document Comment");
    element.getParentNode().insertBefore(comment, element);
  }
}

Find all elements with the name "entry" and append a comment

import java.io.File;
import javax.xml.parsers.DocumentBuilderFactory;
import org.w3c.dom.rument;
import org.w3c.dom.Document;
import org.w3c.dom.Element;
import org.w3c.dom.NodeList;
public class Main {
  public static void main(String[] argv) throws Exception {
    DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();
    factory.setValidating(true);
    factory.setExpandEntityReferences(false);
    Document doc = factory.newDocumentBuilder().parse(new File("filename"));
    NodeList list = doc.getElementsByTagName("entry");
    for (int i = 0; i < list.getLength(); i++) {
      Element element = (Element) list.item(i);
      Comment comment = doc.createComment("index=" + i);
      element.getParentNode().insertBefore(comment, element.getNextSibling());
    }
  }
}

Ignoring Comments While Parsing an XML File

import java.io.File;
import javax.xml.parsers.DocumentBuilderFactory;
import org.w3c.dom.Document;
public class Main {
  public static void main(String[] argv) throws Exception{
    DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();
    factory.setIgnoringComments(true);
    Document doc = factory.newDocumentBuilder().parse(new File("infilename.xml"));
  }
}

Insert a comment in front of the element node

import java.io.File;
import javax.xml.parsers.DocumentBuilderFactory;
import org.w3c.dom.rument;
import org.w3c.dom.Document;
import org.w3c.dom.Element;
public class Main {
  public static void main(String[] argv) throws Exception {
    DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();
    factory.setValidating(true);
    factory.setExpandEntityReferences(false);
    Document doc = factory.newDocumentBuilder().parse(new File("filename"));
    Element element = doc.getElementById("key1");
    element = doc.createElement("root");
    doc.appendChild(element);
    Comment comment = doc.createComment("a comment");
    doc.insertBefore(comment, element);
  }
}

"--" must never appear in the text used to create the comment

import java.io.File;
import javax.xml.parsers.DocumentBuilderFactory;
import org.w3c.dom.rument;
import org.w3c.dom.Document;
public class Main {
  public static void main(String[] argv) throws Exception {
    DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();
    factory.setValidating(true);
    factory.setExpandEntityReferences(false);
    Document doc = factory.newDocumentBuilder().parse(new File("filename"));
    Comment comment = doc.createComment("invalid -- comment");
    boolean validComment = comment.getNodeValue().indexOf("--") < 0;
  }
}