How to modify a xml file?

Question

I use JAXP 1.1 to read a xml file as a DOM tree. I can make change to the DOM tree in the memory, such as add an element or change the node value, but how can I apply these changes to the source xml file, i.e., write the changes back to the disk?

Answer 1

you can write an xml file using DOMWriter.
copy and compile this class
and then use it:
PrintWriter printWriter = //create a printWriter form your xml file
DOMWriter writer = new DOMWriter(printWriter);
writer.print(myXml.toString());
package Zeus.core.XML;
import java.io.*;
import org.w3c.dom.*;
* @author Rodrigo Gonzalez Asensio
* @email [email protected]
public class DOMWriter {
   protected PrintWriter out;
   protected boolean canonical;
   protected String encoding;
public DOMWriter(OutputStreamWriter out) throws UnsupportedEncodingException {
     this(out, false);
public DOMWriter(OutputStreamWriter out, boolean canonical)
     throws UnsupportedEncodingException {
     encoding = out.getEncoding();
     if (encoding == null) {
          throw new UnsupportedEncodingException(out.getEncoding());
     this.out = new PrintWriter(out);
     this.canonical = canonical;
/** Normalizes the given string. */
protected String normalize(String s) {
     StringBuffer str = new StringBuffer();
     int len = (s != null) ? s.length() : 0;
     for (int i = 0; i < len; i++) {
          char ch = s.charAt(i);
          switch (ch) {
               case '<' :
                         str.append("<");
                         break;
               case '>' :
                         str.append(">");
                         break;
               case '&' :
                         str.append("&");
                         break;
               case '"' :
                         str.append(""");
                         break;
               case '\r' :
               case '\n' :
                         if (canonical) {
                              str.append("&#");
                              str.append(Integer.toString(ch));
                              str.append(';');
                              break;
                         // else, default append char
               default :
                         str.append(ch);
     return (str.toString());
public void print(Node node) {
     // is there anything to do?
     if (node == null) {
          return;
     int type = node.getNodeType();
     switch (type) {
          // print document
          case Node.DOCUMENT_NODE :
                    if (!canonical) {
                         out.println("<?xml version=\"1.0\" encoding=\"" + encoding + "\"?>");
                    print(((Document) node).getDocumentElement());
                    out.flush();
                    break;
               // print element with attributes
          case Node.ELEMENT_NODE :
                    out.print('<');
                    out.print(node.getNodeName());
                    Attr attrs[] = sortAttributes(node.getAttributes());
                    for (int i = 0; i < attrs.length; i++) {
                         Attr attr = attrs;
                         out.print(' ');
                         out.print(attr.getNodeName());
                         out.print("=\"");
                         out.print(normalize(attr.getNodeValue()));
                         out.print('"');
                    out.print('>');
                    NodeList children = node.getChildNodes();
                    if (children != null) {
                         int len = children.getLength();
                         for (int i = 0; i < len; i++) {
                              print(children.item(i));
                    break;
               // handle entity reference nodes
          case Node.ENTITY_REFERENCE_NODE :
                    if (canonical) {
                         NodeList children = node.getChildNodes();
                         if (children != null) {
                              int len = children.getLength();
                              for (int i = 0; i < len; i++) {
                                   print(children.item(i));
                    } else {
                         out.print('&');
                         out.print(node.getNodeName());
                         out.print(';');
                    break;
               // print cdata sections
          case Node.CDATA_SECTION_NODE :
                    if (canonical) {
                         out.print(normalize(node.getNodeValue()));
                    } else {
                         out.print("<![CDATA[");
                         out.print(node.getNodeValue());
                         out.print("]]>");
                    break;
               // print text
          case Node.TEXT_NODE :
                    out.print(normalize(node.getNodeValue()));
                    break;
               // print processing instruction
          case Node.PROCESSING_INSTRUCTION_NODE :
                    out.print("<?");
                    out.print(node.getNodeName());
                    String data = node.getNodeValue();
                    if (data != null && data.length() > 0) {
                         out.print(' ');
                         out.print(data);
                    out.print("?>");
                    break;
     if (type == Node.ELEMENT_NODE) {
          out.print("</");
          out.print(node.getNodeName());
          out.print('>');
     out.print("\n");
     out.flush();
} // print(Node)
* Returns a sorted list of attributes
protected Attr[] sortAttributes(NamedNodeMap attrs) {
     int len = (attrs != null) ? attrs.getLength() : 0;
     Attr array[] = new Attr[len];
     for (int i = 0; i < len; i++) {
          array[i] = (Attr) attrs.item(i);
     for (int i = 0; i < len - 1; i++) {
          String name = array[i].getNodeName();
          int index = i;
          for (int j = i + 1; j < len; j++) {
               String curName = array[j].getNodeName();
               if (curName.compareTo(name) < 0) {
                    name = curName;
                    index = j;
          if (index != i) {
               Attr temp = array[i];
               array[i] = array[index];
               array[index] = temp;
     return (array);
regards.