Can anyone help?I still can't append records in xml...

[Mellihoney Michael]

the servlet class:

 
import beans.*;
import javax.servlet.*;
import javax.servlet.http.*;
import java.io.*;
import java.util.*;
import javax.xml.parsers.*;
import org.w3c.dom.*;
import  org.apache.xml.serialize.OutputFormat;//formating and serializing xml output
import  org.apache.xml.serialize.Serializer;
import  org.apache.xml.serialize.SerializerFactory;
import  org.apache.xml.serialize.XMLSerializer;
public class BookServlet extends HttpServlet {
  /*
   * insertBookToSession
   */
  private boolean insertBookToSession(HttpServletRequest request) throws ServletException, IOException {
    String title = request.getParameter("title");
    String author = request.getParameter("author");
    String isbn = request.getParameter("isbn");
    String publisher = request.getParameter("publisher");
    String publisherCountry = request.getParameter("publisherCountry");
  BookBean newBook = new BookBean(title, author, isbn, publisher, publisherCountry);
  HttpSession session= request.getSession(true);//retrieve session object
  Object books = session.getAttribute("BOOKLIST");//retrieve "BOOKLIST" from session object
//"BOOKLIST" is an array of BookBean
  if (books == null) {//if no booklist stored in seession object
  BookBean [] newbooklist  = new BookBean [10];//create a new booklist with 10 elements
  newbooklist[0] = newBook;//add first book to the lis
  session.setAttribute("BOOKLIST", newbooklist);//insert the booklist into session object
  return true;
  }
  else {
  BookBean [] booklist = (BookBean []) books;
  int newbookindex = 10;//if newbookindex = 10 : represents book list is full
  for (int i=0; i<10; i++) {
    if (booklist[i] == null) {
     newbookindex = i;
     break;
    }
  }
  if (newbookindex == 10) {//booklist is full
  return false;
  }
  else {//booklist is NOT full
  booklist[newbookindex] = newBook;
  session.setAttribute("BOOKLIST", booklist);
  return true;
  }
 }
 }
  
  /*
   * generateDOM
   */
  private Document generateDOM(HttpServletRequest request) throws ServletException, IOException {
DocumentBuilderFactory factory;
DocumentBuilder builder;
try {
factory = DocumentBuilderFactory.newInstance();
builder = factory.newDocumentBuilder();
}
catch (ParserConfigurationException pe) {
throw new IOException("ParserConfiguration problem");
}
  Document document=builder.newDocument();
Element root = document.createElement("booklist");
document.appendChild(root);
HttpSession session= request.getSession(true);//assume there is always a session exist
Object books = session.getAttribute("BOOKLIST");//assume there is always an attribute contain a list of book
//you should do proper checking here in your project.
BookBean [] booklist  = (BookBean []) books;//assume the list contains at most 10 books
int bookcount = 0;
for (int i=0; i<booklist.length; i++) {
if (booklist[i] != null)
bookcount++;
else
continue;
}
//creating the domcument tree that store the records in "BOOKLIST"
for (int j=0; j<bookcount; j++) {
Element bookElement = document.createElement("book");
Element bookTitleElement = document.createElement("title");
Text textnode1 = document.createTextNode(booklist[j].getTitle());
bookTitleElement.appendChild(textnode1);
bookElement.appendChild(bookTitleElement);
Element bookAuthorElement = document.createElement("author");
Text textnode2 = document.createTextNode(booklist[j].getAuthor());
bookAuthorElement.appendChild(textnode2);
bookElement.appendChild(bookAuthorElement);
Element bookISBNElement = document.createElement("isbn");
Text textnode3 = document.createTextNode(booklist[j].getIsbn());
bookISBNElement.appendChild(textnode3);
bookElement.appendChild(bookISBNElement);
Element bookPublisherElement = document.createElement("publisher");
Element publisherNameElement = document.createElement("name");
Text textnode4 = document.createTextNode(booklist[j].getPublisher());
publisherNameElement.appendChild(textnode4);
bookPublisherElement.appendChild(publisherNameElement);
Element publisherCountryElement = document.createElement("country");
Text textnode5 = document.createTextNode(booklist[j].getPublisherCountry());
publisherCountryElement.appendChild(textnode5);
bookPublisherElement.appendChild(publisherCountryElement);
bookElement.appendChild(bookPublisherElement);
root.appendChild(bookElement);
}
  return document;
  }
  /*
   * generateXMLDocument
   */
  public void generateXMLDocument (Document document) throws IOException {
   
File newXMLFile = new File("..//webapps//Sample//xml//booklist.xml");
  
FileWriter xmlwriter = new FileWriter(newXMLFile,true);//append the records
  StringWriter stringOut = new StringWriter();     //Writer will be a String
OutputFormat xmlformat = new OutputFormat(document);
xmlformat.setIndenting(true);
XMLSerializer serializer1 = new XMLSerializer(xmlwriter, xmlformat);
XMLSerializer serializer2 = new XMLSerializer(stringOut, xmlformat);
serializer1.asDOMSerializer();
serializer2.asDOMSerializer();
serializer1.serialize(document.getDocumentElement());
serializer2.serialize(document.getDocumentElement());
System.out.println( "" + stringOut.toString() );
System.out.println("Output completed");
  }

  /*
   * doGet
   */
  public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    doPost(request, response);
  }

  /*
   * doPost
   */
  public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    String action = request.getParameter("action");
    if (action != null && action.equals("SAVE")) {
if (insertBookToSession(request)) {
response.sendRedirect("../jsp/Book.html");
}
else {
response.sendRedirect("../jsp/ListFullError.html");
}
}
else if (action != null && action.equals("CREATE XML")) {
Document newDOMTree = generateDOM(request);
generateXMLDocument(newDOMTree);
HttpSession session= request.getSession(true);//retrieve session object and remove "BOOKLIST"
session.removeAttribute("BOOKLIST");
response.sendRedirect("../jsp/Book.html");
}
  }

}
 

the bean class:

 
package beans;
public class BookBean {
private String title;
private String author;
private String isbn;
private String publisher;
private String publisherCountry;

public BookBean () {}
public BookBean (String t, String a, String i, String p, String pc) {
title = t;
author = a;
isbn = i;
publisher = p;
publisherCountry = pc;
}

public void setTitle (String t) {
title = t;
}
public void setAuthor (String a) {
author = a;
}
public void setIsbn (String i) {
isbn = i;
}
public void setPublisher (String p) {
publisher = p;
}
public void setPublisherCountry (String pc) {
publisherCountry = pc;
}
public String getTitle () {
return title;
}
public String getAuthor () {
return author;
}
public String getIsbn () {
return isbn;
}
public String getPublisher () {
return publisher;
}
public String getPublisherCountry () {
return publisherCountry;
}
public void clear () {
title = author = isbn = publisher = publisherCountry = null;
}
}
 

At first time,the xml is not existed.I add the the first records in this xml file while the file is created:
It appears like:

<?xml version="1.0" encoding="UTF-8"?>
<booklist>
    <book>
        <title>1</title>
        <author>1</author>
        <isbn>1234</isbn>
        <publisher>
            <name>111</name>
            <country>111</country>
        </publisher>
    </book>
</booklist>

but when i add the second record:
it appears like:

<?xml version="1.0" encoding="UTF-8"?>
<booklist>
    <book>
        <title>1</title>
        <author>1</author>
        <isbn>1234</isbn>
        <publisher>
            <name>111</name>
            <country>111</country>
        </publisher>
    </book>
</booklist>
//how to avoid this sentence to be wirtten into xml file
<?xml version="1.0" encoding="UTF-8"?>
<booklist>
    <book>
        <title>1</title>
        <author>1</author>
        <isbn>101-90876-1000</isbn>
        <publisher>
            <name>2</name>
            <country>1</country>
        </publisher>
    </book>
</booklist>

Can anyone explain me how to cope with the duplicated "<?xml version="1.0" encoding="UTF-8"?>"???
Thanks in advance....
[ January 11, 2004: Message edited by: Mellihoney Michael ]

[Frank Carver]

Can anyone explain me how to cope with the duplicated "<?xml version="1.0" encoding="UTF-8"?>"???
You've got more problems than just that. A valid XML document can have only one "root" element (in your case <booklist> . You really need to rethink how you do this. A simple "append" to a file of serialized XML is never a valid operation.
Essentially it seems you have three choices:

to do your "append", read in the existing file to a DOM, add your new node to the document, and re-serialize the whole thing out to the file.

store your uploaded information in some simpler structure (a database, a CSV file, in memory etc.) where an "append" is simpler, and regenerate the XML file from this intermediate structure each time anything is added

store your uploaded information in some simpler structure (a database, a CSV file, in memory etc.) where an "append" is simpler, and generate the XML file only when it is asked for

Which of these options you choose depends on how many times you think the XML file is likely to be read compared to the number of times it will be written, and how many items you think it is likely to contain in total.

[Mellihoney Michael]

thanks
Frank

[Mellihoney Michael]

Frank,please help:
I choose the first method (READ IN DOM and re-serialize).
I have changed the servlet as the following:

  
import beans.*;//Java bean for book
import javax.servlet.*;
import javax.servlet.http.*;
import java.io.*;
import java.util.*;
import javax.xml.parsers.*;
import org.w3c.dom.*;
import  org.apache.xml.serialize.OutputFormat;//formating and serializing xml output
import  org.apache.xml.serialize.Serializer;
import  org.apache.xml.serialize.SerializerFactory;
import  org.apache.xml.serialize.XMLSerializer;
public class BookServlet extends HttpServlet {
  /*
   * insertBookToSession
   */
  private boolean insertBookToSession(HttpServletRequest request) throws ServletException, IOException {
    String title = request.getParameter("title");
    String author = request.getParameter("author");
    String isbn = request.getParameter("isbn");
    String publisher = request.getParameter("publisher");
    String publisherCountry = request.getParameter("publisherCountry");
  BookBean newBook = new BookBean(title, author, isbn, publisher, publisherCountry);
  HttpSession session= request.getSession(true);//retrieve session object
  Object books = session.getAttribute("BOOKLIST");//retrieve "BOOKLIST" from session object
//"BOOKLIST" is an array of BookBean
  if (books == null) {//if no booklist stored in seession object
  BookBean [] newbooklist  = new BookBean [10];//create a new booklist with 10 elements
  newbooklist[0] = newBook;//add first book to the lis
  session.setAttribute("BOOKLIST", newbooklist);//insert the booklist into session object
  return true;
  }
  else {
  BookBean [] booklist = (BookBean []) books;
  int newbookindex = 10;//if newbookindex = 10 : represents book list is full
  for (int i=0; i<10; i++) {
    if (booklist[i] == null) {
     newbookindex = i;
     break;
    }
  }
  if (newbookindex == 10) {//booklist is full
  return false;
  }
  else {//booklist is NOT full
  booklist[newbookindex] = newBook;
  session.setAttribute("BOOKLIST", booklist);
  return true;
  }
 }
 }
  
  /*
   * if XML file is existed
   */ 
  private boolean isXMLFileCreated(){
    boolean exists=new File("..//webapps//Sample//xml//booklist.xml").exists();
    return exists;
  }

  /*
   * read existing XML file
   */  
  public Document readXMLFile() throws ServletException, IOException {
    Document documentIn=null;
    Document documentOut=null;
    try {
     //create an input source
     File xmlFile = new File("..//webapps//Sample//xml//booklist.xml");
     //launch a DocumentBuilderFactory
     DocumentBuilderFactory docFactory = DocumentBuilderFactory.newInstance();
     // launch a DocumentBuilder
     DocumentBuilder docBuilder = docFactory.newDocumentBuilder();
     documentIn = docBuilder.parse(xmlFile);
     documentOut = docBuilder.newDocument();
     //get node
     Node rootNode = documentIn.getDocumentElement();
     System.out.println("The root node is : "+rootNode.getNodeName()+ "\n");
     //append root
   Element root = documentOut.createElement(rootNode.getNodeName());
   documentOut.appendChild(root);
     /*//get attributes
     NamedNodeMap nnm1 = rootNode.getAttributes();
     if (nnm1!= null) {
       for (int i=0;i < nnm1.getLength(); i++) {
          Node n1 = nnm1.item(i);
          System.out.println("The attribute name is : "+n1.getNodeName()+ " and the attribute value is - "+n1.getNodeValue()+"\n");      
       }
     }*/
     //get the children of the root element and process ALL the child node.
     NodeList children = rootNode.getChildNodes();
     for (int i=0;i < children.getLength(); i++) {
       //get child node
       Node childNode = children.item(i);
       System.out.println("The child node is : "+childNode.getNodeName()+ " and the node value is: "+childNode.getNodeValue()+"\n");
       //append child node
   Element childElement = documentOut.createElement(childNode.getNodeName());
   Text textnode = documentOut.createTextNode(childNode.getNodeValue());
   childElement.appendChild(textnode);
     root.appendChild(childElement);
       // nested loop to find nested elements
       if (childNode.hasChildNodes()){
         recursiveFindingChild(childNode,childElement,documentOut);
       }
     }
    }
    catch (Exception e){
     //
    }
 
    return documentOut;
   }

  /* recursive finding child - algorithm for own servlet use */
  private void recursiveFindingChild(Node parentNode,Element parentElement,Document documentOut) throws ServletException{
     NodeList children = parentNode.getChildNodes();
     for (int i=0;i < children.getLength(); i++) {
       //deep child node
       Node childNode = children.item(i);
       System.out.println("The deep child node is : "+childNode.getNodeName()+ " and the node value is: "+childNode.getNodeValue()+"\n");
       //append deep child node
   Element childElement = documentOut.createElement(childNode.getNodeName());
   Text textnode = documentOut.createTextNode(childNode.getNodeValue());
   childElement.appendChild(textnode);
     parentElement.appendChild(childElement);    
       /*
       NamedNodeMap nnm2 = n.getAttributes();
       if (nnm2!= null) {
         for (int j=0;j < nnm2.getLength(); j++) {
           Node n2 = nnm2.item(j);
           System.out.println("The attribute name is :"+n2.getNodeName()+ "; and the attribute value is - "+n2.getNodeValue()+"\n");
         }
       }
       */
       // nested loop to find nested elements
       if (childNode.hasChildNodes()){
         recursiveFindingChild(parentNode,parentElement,documentOut);
       }
     }
   }

  /*
   * reorgDOM
   */
  private Document reorgDOM(HttpServletRequest request,Document d) throws ServletException, IOException {
DocumentBuilderFactory factory;
DocumentBuilder builder;
try {
factory = DocumentBuilderFactory.newInstance();
builder = factory.newDocumentBuilder();
}
catch (ParserConfigurationException pe) {
throw new IOException("ParserConfiguration problem");
}
  
  //build the document
  Document document = builder.newDocument();
  Document documentIn = d;
  //append root
Element root = document.createElement("booklist");
document.appendChild(root);

  // ADD PREVIOUS ONES
     //get node
     Node rootNode = documentIn.getDocumentElement();
     System.out.println("The root node is : "+rootNode.getNodeName()+ "\n");
     //get the children of the root element and process ALL the child node.
     NodeList children = rootNode.getChildNodes();
     for (int i=0;i < children.getLength(); i++) {
       //get child node
       Node childNode = children.item(i);
       System.out.println("The child node is : "+childNode.getNodeName()+ " and the node value is: "+childNode.getNodeValue()+"\n");
       //append child node
   Element childElement = document.createElement(childNode.getNodeName());
   Text textnode = document.createTextNode(childNode.getNodeValue());
   childElement.appendChild(textnode);
     root.appendChild(childElement);
       // nested loop to find nested elements
       if (childNode.hasChildNodes()){
         recursiveFindingChild(childNode,childElement,document);
       }
     }

  // ADD NEW RECORDS
HttpSession session= request.getSession(true);//assume there is always a session exist
Object books = session.getAttribute("BOOKLIST");//assume there is always an attribute contain a list of book
BookBean [] booklist  = (BookBean []) books;//assume the list contains at most 10 books
int bookcount = 0;
for (int i=0; i<booklist.length; i++) {
if (booklist[i] != null)
bookcount++;
else
continue;
}
//creating the domcument tree that store the records in "BOOKLIST"
for (int j=0; j<bookcount; j++) {
Element bookElement = document.createElement("book");
Element bookTitleElement = document.createElement("title");
Text textnode1 = document.createTextNode(booklist[j].getTitle());
bookTitleElement.appendChild(textnode1);
bookElement.appendChild(bookTitleElement);
Element bookAuthorElement = document.createElement("author");
Text textnode2 = document.createTextNode(booklist[j].getAuthor());
bookAuthorElement.appendChild(textnode2);
bookElement.appendChild(bookAuthorElement);
Element bookISBNElement = document.createElement("isbn");
Text textnode3 = document.createTextNode(booklist[j].getIsbn());
bookISBNElement.appendChild(textnode3);
bookElement.appendChild(bookISBNElement);
Element bookPublisherElement = document.createElement("publisher");
Element publisherNameElement = document.createElement("name");
Text textnode4 = document.createTextNode(booklist[j].getPublisher());
publisherNameElement.appendChild(textnode4);
bookPublisherElement.appendChild(publisherNameElement);
Element publisherCountryElement = document.createElement("country");
Text textnode5 = document.createTextNode(booklist[j].getPublisherCountry());
publisherCountryElement.appendChild(textnode5);
bookPublisherElement.appendChild(publisherCountryElement);
bookElement.appendChild(bookPublisherElement);
root.appendChild(bookElement);
}
  return document;
  }

  /*
   * generateDOM
   */
  private Document generateDOM(HttpServletRequest request) throws ServletException, IOException {
DocumentBuilderFactory factory;
DocumentBuilder builder;
try {
factory = DocumentBuilderFactory.newInstance();
builder = factory.newDocumentBuilder();
}
catch (ParserConfigurationException pe) {
throw new IOException("ParserConfiguration problem");
}
  
  //build the document
  Document document = builder.newDocument();
  //append root
Element root = document.createElement("booklist");
document.appendChild(root);

  // ADD NEW RECORDS
HttpSession session= request.getSession(true);//assume there is always a session exist
Object books = session.getAttribute("BOOKLIST");//assume there is always an attribute contain a list of book
BookBean [] booklist  = (BookBean []) books;//assume the list contains at most 10 books
int bookcount = 0;
for (int i=0; i<booklist.length; i++) {
if (booklist[i] != null)
bookcount++;
else
continue;
}
//creating the domcument tree that store the records in "BOOKLIST"
for (int j=0; j<bookcount; j++) {
Element bookElement = document.createElement("book");
Element bookTitleElement = document.createElement("title");
Text textnode1 = document.createTextNode(booklist[j].getTitle());
bookTitleElement.appendChild(textnode1);
bookElement.appendChild(bookTitleElement);
Element bookAuthorElement = document.createElement("author");
Text textnode2 = document.createTextNode(booklist[j].getAuthor());
bookAuthorElement.appendChild(textnode2);
bookElement.appendChild(bookAuthorElement);
Element bookISBNElement = document.createElement("isbn");
Text textnode3 = document.createTextNode(booklist[j].getIsbn());
bookISBNElement.appendChild(textnode3);
bookElement.appendChild(bookISBNElement);
Element bookPublisherElement = document.createElement("publisher");
Element publisherNameElement = document.createElement("name");
Text textnode4 = document.createTextNode(booklist[j].getPublisher());
publisherNameElement.appendChild(textnode4);
bookPublisherElement.appendChild(publisherNameElement);
Element publisherCountryElement = document.createElement("country");
Text textnode5 = document.createTextNode(booklist[j].getPublisherCountry());
publisherCountryElement.appendChild(textnode5);
bookPublisherElement.appendChild(publisherCountryElement);
bookElement.appendChild(bookPublisherElement);
root.appendChild(bookElement);
}
  return document;
  }
  /*
   * generateXMLDocument
   */
  public void generateXMLDocument (Document document) throws IOException {
   
File newXMLFile = new File("..//webapps//Sample//xml//booklist.xml");
  
FileWriter xmlwriter = new FileWriter(newXMLFile);
  StringWriter stringOut = new StringWriter();     //Writer will be a String
OutputFormat xmlformat = new OutputFormat(document);
xmlformat.setIndenting(true);
XMLSerializer serializer1 = new XMLSerializer(xmlwriter, xmlformat);
XMLSerializer serializer2 = new XMLSerializer(stringOut, xmlformat);
serializer1.asDOMSerializer();
serializer2.asDOMSerializer();
serializer1.serialize(document.getDocumentElement());
serializer2.serialize(document.getDocumentElement());
System.out.println( "" + stringOut.toString() );
System.out.println("Output completed");
  }

  /*
   * doGet
   */
  public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    doPost(request, response);
  }

  /*
   * doPost
   */
  public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    String action = request.getParameter("action");
    if (action != null && action.equals("SAVE")) {
  if (insertBookToSession(request)) {
  response.sendRedirect("../jsp/Book.html");
  }
  else {
  response.sendRedirect("../jsp/ListFullError.html");
  }
  }
  else if (action != null && action.equals("CREATE XML")) {
      try{
        if (!isXMLFileCreated()){
       Document newDOMTree = generateDOM(request);
      generateXMLDocument(newDOMTree);
      HttpSession session= request.getSession(true);//retrieve session object and remove "BOOKLIST"
      session.removeAttribute("BOOKLIST");
      response.sendRedirect("../jsp/Book.html");
        }
        else{
          Document newDOMTree = reorgDOM(request,readXMLFile());
          System.out.println(readXMLFile());
      generateXMLDocument(newDOMTree);
      HttpSession session= request.getSession(true);//retrieve session object and remove "BOOKLIST"
      session.removeAttribute("BOOKLIST");
      response.sendRedirect("../jsp/Book.html");
        }
      }
      catch (Exception e){
        //
      }
  }
  }
}

but when I add new records, it always overwrites the previous one,why?

<?xml version="1.0" encoding="UTF-8"?>
<booklist>
    <book>
        <title>Titanic</title>
        <author>Mic</author>
        <isbn>101-90876-1000</isbn>
        <publisher>
            <name>Mic</name>
            <country>England</country>
        </publisher>
    </book>
</booklist>

WHEN I ADD A NEW RECORD:

<?xml version="1.0" encoding="UTF-8"?>
<booklist>
    <book>
        <title>JAVA</title>
        <author>Kevin</author>
        <isbn>101-90876-1000</isbn>
        <publisher>
            <name>Mic</name>
            <country>USA</country>
        </publisher>
    </book>
</booklist>

IT TURNS OUT:

<booklist>
    <book>
        <title>JAVA</title>
        <author>Kevin</author>
        <isbn>101-90876-1000</isbn>
        <publisher>
            <name>Mic</name>
            <country>USA</country>
        </publisher>
    </book>
</booklist>

INSTEAD OF :

<?xml version="1.0" encoding="UTF-8"?>
<booklist>
    <book>
        <title>Titanic</title>
        <author>Mic</author>
        <isbn>101-90876-1000</isbn>
        <publisher>
            <name>Mic</name>
            <country>England</country>
        </publisher>
    </book>
    <book>
        <title>JAVA</title>
        <author>Kevin</author>
        <isbn>101-90876-1000</isbn>
        <publisher>
            <name>Mic</name>
            <country>USA</country>
        </publisher>
    </book>
</booklist>

And I couldn't find where is going wrong...
could u help me?

[ January 11, 2004: Message edited by: Mellihoney Michael ]

[Frank Carver]

Hmm. It's difficult to tell. You have a lot of code there, some of it duplicated, and most of it grouped into pretty big methods with side effects - all of which makes for hard-to-test code. On the other hand, you seem to have plenty of diagnostic printouts - what did they produce? What DOM is being loaded when you read the existing flle? What DOM is being created when you append your new nodes?
I am worried that you have put a gag in the mouth of your system by silently swallowing exceptions, though. An empty catch-block is never a good idea, and one that catches Exception is particularly awful. You simply lose the information if your program is throwing an exception or not. Please put an e.printStackTrace() in your catch block, and let us know what it says.

[Mellihoney Michael]

I listed methods which may cause potential errors:

  /*
   * read existing XML file - DOM used when readind the existing flle
   */  
  public Document readXMLFile() throws ServletException, IOException {
    Document documentIn=null;
    Document documentOut=null;
    try {
     //create an input source
     File xmlFile = new File("..//webapps//Sample//xml//booklist.xml");
     //launch a DocumentBuilderFactory
     DocumentBuilderFactory docFactory = DocumentBuilderFactory.newInstance();
     // launch a DocumentBuilder
     DocumentBuilder docBuilder = docFactory.newDocumentBuilder();
     documentIn = docBuilder.parse(xmlFile);
     documentOut = docBuilder.newDocument();
     //get node
     Node rootNode = documentIn.getDocumentElement();                                        
                                                                             //*******************************
     System.out.println("The root node is : "+rootNode.getNodeName()+ "\n"); //****it prints out "booklist"***
                                                                             //*******************************  
     //append root
   Element root = documentOut.createElement(rootNode.getNodeName());
   documentOut.appendChild(root);
     /*//get attributes
     NamedNodeMap nnm1 = rootNode.getAttributes();
     if (nnm1!= null) {
       for (int i=0;i < nnm1.getLength(); i++) {
          Node n1 = nnm1.item(i);
          System.out.println("The attribute name is : "+n1.getNodeName()+ " and the attribute value is - "+n1.getNodeValue()+"\n");      
       }
     }*/
     //get the children of the root element and process ALL the child node.
     NodeList children = rootNode.getChildNodes();
     for (int i=0;i < children.getLength(); i++) {
       //get child node
                                          //*****************************************************************
       Node childNode = children.item(i); //********  it says in RunTime that childNode is null,why?   ******
       System.out.println(childNode);     //*****************************************************************                                              
       System.out.println("The child node is : "+childNode.getNodeName()+ " and the node value is: "+childNode.getNodeValue()+"\n");
       //append child node
   Element childElement = documentOut.createElement(childNode.getNodeName());
   Text textnode = documentOut.createTextNode(childNode.getNodeValue());
   childElement.appendChild(textnode);
     root.appendChild(childElement);
       // nested loop to find nested elements
       if (childNode.hasChildNodes()){
         recursiveFindingChild(childNode,childElement,documentOut);
       }
     }
    }
    catch (Exception e){
     e.printStackTrace();//DOMException because of the null childNode
    }
 
    return documentOut;
   }

  /*
   * reorgDOM - DOM used when appending new nodes
   */
  private Document reorgDOM(HttpServletRequest request,Document d) throws ServletException, IOException {
DocumentBuilderFactory factory;
DocumentBuilder builder;
try {
factory = DocumentBuilderFactory.newInstance();
builder = factory.newDocumentBuilder();
}
catch (ParserConfigurationException pe) {
throw new IOException("ParserConfiguration problem");
}
  
  //build the document
  Document document = builder.newDocument();
  Document documentIn = d;
  //append root
Element root = document.createElement("booklist");
document.appendChild(root);

  // ADD PREVIOUS ONES
     //get node
     Node rootNode = documentIn.getDocumentElement();
     System.out.println("The root node is : "+rootNode.getNodeName()+ "\n");
     //get the children of the root element and process ALL the child node.
     NodeList children = rootNode.getChildNodes();
     for (int i=0;i < children.getLength(); i++) {
       //get child node
       Node childNode = children.item(i);
       System.out.println("The child node is : "+childNode.getNodeName()+ " and the node value is: "+childNode.getNodeValue()+"\n");
       //append child node
   Element childElement = document.createElement(childNode.getNodeName());
   Text textnode = document.createTextNode(childNode.getNodeValue());
   childElement.appendChild(textnode);
     root.appendChild(childElement);
       // nested loop to find nested elements
       if (childNode.hasChildNodes()){
         recursiveFindingChild(childNode,childElement,document);
       }
     }

  // ADD NEW RECORDS
HttpSession session= request.getSession(true);
Object books = session.getAttribute("BOOKLIST");
BookBean [] booklist  = (BookBean []) books;
int bookcount = 0;
for (int i=0; i<booklist.length; i++) {
if (booklist[i] != null)
bookcount++;
else
continue;
}
//creating the domcument tree that store the records in "BOOKLIST"
for (int j=0; j<bookcount; j++) {
Element bookElement = document.createElement("book");
Element bookTitleElement = document.createElement("title");
Text textnode1 = document.createTextNode(booklist[j].getTitle());
bookTitleElement.appendChild(textnode1);
bookElement.appendChild(bookTitleElement);
Element bookAuthorElement = document.createElement("author");
Text textnode2 = document.createTextNode(booklist[j].getAuthor());
bookAuthorElement.appendChild(textnode2);
bookElement.appendChild(bookAuthorElement);
Element bookISBNElement = document.createElement("isbn");
Text textnode3 = document.createTextNode(booklist[j].getIsbn());
bookISBNElement.appendChild(textnode3);
bookElement.appendChild(bookISBNElement);
Element bookPublisherElement = document.createElement("publisher");
Element publisherNameElement = document.createElement("name");
Text textnode4 = document.createTextNode(booklist[j].getPublisher());
publisherNameElement.appendChild(textnode4);
bookPublisherElement.appendChild(publisherNameElement);
Element publisherCountryElement = document.createElement("country");
Text textnode5 = document.createTextNode(booklist[j].getPublisherCountry());
publisherCountryElement.appendChild(textnode5);
bookPublisherElement.appendChild(publisherCountryElement);
bookElement.appendChild(bookPublisherElement);
root.appendChild(bookElement);
}
  return document;
  }

  /*
   * generateDOM - DOM used when creating file at the first time
   */
  private Document generateDOM(HttpServletRequest request) throws ServletException, IOException {
DocumentBuilderFactory factory;
DocumentBuilder builder;
try {
factory = DocumentBuilderFactory.newInstance();
builder = factory.newDocumentBuilder();
}
catch (ParserConfigurationException pe) {
throw new IOException("ParserConfiguration problem");
}
  
  //build the document
  Document document = builder.newDocument();
  //append root
Element root = document.createElement("booklist");
document.appendChild(root);

  // ADD NEW RECORDS
HttpSession session= request.getSession(true);
Object books = session.getAttribute("BOOKLIST");
BookBean [] booklist  = (BookBean []) books;
int bookcount = 0;
for (int i=0; i<booklist.length; i++) {
if (booklist[i] != null)
bookcount++;
else
continue;
}
//creating the domcument tree that store the records in "BOOKLIST"
for (int j=0; j<bookcount; j++) {
Element bookElement = document.createElement("book");
Element bookTitleElement = document.createElement("title");
Text textnode1 = document.createTextNode(booklist[j].getTitle());
bookTitleElement.appendChild(textnode1);
bookElement.appendChild(bookTitleElement);
Element bookAuthorElement = document.createElement("author");
Text textnode2 = document.createTextNode(booklist[j].getAuthor());
bookAuthorElement.appendChild(textnode2);
bookElement.appendChild(bookAuthorElement);
Element bookISBNElement = document.createElement("isbn");
Text textnode3 = document.createTextNode(booklist[j].getIsbn());
bookISBNElement.appendChild(textnode3);
bookElement.appendChild(bookISBNElement);
Element bookPublisherElement = document.createElement("publisher");
Element publisherNameElement = document.createElement("name");
Text textnode4 = document.createTextNode(booklist[j].getPublisher());
publisherNameElement.appendChild(textnode4);
bookPublisherElement.appendChild(publisherNameElement);
Element publisherCountryElement = document.createElement("country");
Text textnode5 = document.createTextNode(booklist[j].getPublisherCountry());
publisherCountryElement.appendChild(textnode5);
bookPublisherElement.appendChild(publisherCountryElement);
bookElement.appendChild(bookPublisherElement);
root.appendChild(bookElement);
}
  return document;
  }