reading, updating problem with dom4j library

this is my code to write xml file:

public void generateDocument(){
        Document document = DocumentHelper.createDocument();
             Element catalogElement = document.addElement("catalog");
             catalogElement.addComment("An XML Catalog");
             catalogElement.addProcessingInstruction("target","text");
             Element journalElement =  catalogElement.addElement("journal");
             journalElement.addAttribute("title", "XML Zone");
             journalElement.addAttribute("publisher", "IBM developerWorks");


             Element articleElement=journalElement.addElement("article");
             articleElement.addAttribute("level", "Intermediate");
             articleElement.addAttribute("date", "December-2001");
             Element  titleElement=articleElement.addElement("title");
             titleElement.setText("Java configuration with XML Schema");
             Element authorElement=articleElement.addElement("author");
             Element  firstNameElement=authorElement.addElement("firstname");
             firstNameElement.setText("Marcello");
             Element lastNameElement=authorElement.addElement("lastname");
             lastNameElement.setText("Vitaletti");
                //pass this xml document
             DTDGenerator dtd=new DTDGenerator(document,"catalog.dtd");
             document.addDocType("catalog",
                                 null,"catalog.dtd");
            try{
            XMLWriter output = new XMLWriter(
                    new FileWriter( new File("catalog.xml") ));
                output.write( document );
                output.close();

                }
             catch(IOException e){System.out.println(e.getMessage());}

        }

my reading code is:

public static void modifyDocument(File inputXml){

          try{
           SAXReader saxReader = new SAXReader();
           Document document = saxReader.read(inputXml);

           List list = document.selectNodes("//article/@level" );
           Iterator iter=list.iterator();
           while(iter.hasNext()){
            Attribute attribute=(Attribute)iter.next();
            if(attribute.getValue().equals("Intermediate"))
              attribute.setValue("Introductory"); 

               }

           list = document.selectNodes("//article/@date" );
           iter=list.iterator();
           while(iter.hasNext()){
            Attribute attribute=(Attribute)iter.next();
            if(attribute.getValue().equals("December-2001"))
              attribute.setValue("October-2002");

               }

           list = document.selectNodes("//article" );
           iter=list.iterator();
           while(iter.hasNext()){
            Element element=(Element)iter.next();
            Iterator iterator=element.elementIterator("title");
              while(iterator.hasNext()){
                Element titleElement=(Element)iterator.next();
                if(titleElement.getText().equals("Java configuration with XML Schema"))
                titleElement.setText("Create flexible and extensible XML schema");

                  }

                                        }

            list = document.selectNodes("//article/author" );
            iter=list.iterator();
             while(iter.hasNext()){
             Element element=(Element)iter.next();
             Iterator iterator=element.elementIterator("firstname");
             while(iterator.hasNext()){
              Element firstNameElement=(Element)iterator.next();
              if(firstNameElement.getText().equals("Marcello"))
              firstNameElement.setText("Ayesha");
                                             }

                                      }

            list = document.selectNodes("//article/author" );
            iter=list.iterator();
             while(iter.hasNext()){
              Element element=(Element)iter.next();
              Iterator iterator=element.elementIterator("lastname");
             while(iterator.hasNext()){
              Element lastNameElement=(Element)iterator.next();
              if(lastNameElement.getText().equals("Vitaletti"))
              lastNameElement.setText("Malik");

                                          }

                                       }
             XMLWriter output = new XMLWriter(
              new FileWriter( new File("catalog-modified.xml") ));
             output.write( document );
             output.close();
           }

          catch(DocumentException e)
                         {
                          System.out.println(e.getMessage());
                                    }

          catch(IOException e){
                               System.out.println(e.getMessage());
                            }
         }

I am using dom4j library and also taken help of DTDGenerator to generate dtd file from my created xml. everything working fine at writing part..But reading is cursing me. I believe there is something wrong with my DTD..but my output dtd is quite impressive to look..But not helping in reading the xml:(.开发者_如何学编程. My Dtd ouput:

<!ELEMENT article ( title, author ) >
<!ATTLIST article date NMTOKEN #REQUIRED >
<!ATTLIST article level NMTOKEN #REQUIRED >

<!ELEMENT author ( firstname, lastname ) >

<!ELEMENT catalog ( journal ) >

<!ELEMENT firstname ( #PCDATA ) >

<!ELEMENT journal ( article ) >
<!ATTLIST journal publisher CDATA #REQUIRED >
<!ATTLIST journal title CDATA #REQUIRED >

<!ELEMENT lastname ( #PCDATA ) >

<!ELEMENT title ( #PCDATA ) >

My Xml file is:

<?xml version="1.0" encoding="UTF-8"?>

<!DOCTYPE catalog SYSTEM "catalog.dtd">
-<catalog>
<!--An XML Catalog-->

<?target text?>
-<journal title="XML Zone" publisher="IBM developerWorks">-<article date="December-2001" level="Intermediate"><title>Java configuration with XML Schema</title>-<author><firstname>Marcello</firstname><lastname>Vitaletti</lastname></author></article></journal></catalog>

and the error is:

Exception in thread "main" java.lang.NoClassDefFoundError: org/jaxen/JaxenException
    at org.dom4j.DocumentFactory.createXPath(DocumentFactory.java:230)
    at org.dom4j.tree.AbstractNode.createXPath(AbstractNode.java:207)
    at org.dom4j.tree.AbstractNode.selectNodes(AbstractNode.java:164)
    at com.xmlsample.XMLSampleRead.modifyDocument(XMLSampleRead.java:35)
    at com.xmlsample.XMLSampleRead.main(XMLSampleRead.java:24)
Caused by: java.lang.ClassNotFoundException: org.jaxen.JaxenException
    at java.net.URLClassLoader$1.run(Unknown Source)
    at java.net.URLClassLoader$1.run(Unknown Source)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.net.URLClassLoader.findClass(Unknown Source)
    at java.lang.ClassLoader.loadClass(Unknown Source)
    at sun.misc.Launcher$AppClassLoader.loadClass(Unknown Source)
    at java.lang.ClassLoader.loadClass(Unknown Source)
    ... 5 more

This has nothing to do with your DTD. You need to include jaxen on your classpath. Jaxen is the xpath engine used internally by dom4j when evaluating xpath expressions. Jaxen is part of the dom4j distribution.