Java EE (Java Enterprise Edition) General Discussion

I apologise if this question has been answered before, but I haven't been able to find a precise answer to my problem.

Here is a snippet of my XML file:
<organization...>
<title>
<item...>
<title>
<adlcp:prerequisites>
...


What I want to do is search this file based on item title (org->item->title). When I find the corresponding entry, I want to traverse back up the tree to retrieve an attribute of the <item> tag, the <title> belonging to the organisation, and I also want to record the sibling node <adlcp:prerequisites>.

I have no trouble obtaining traversing up the tree from the item <title>, but as soon as I try calling getFirstChild() or getNextSibling(), my method throws an exception.

Here is an excerpt of my (somewhat shoddy) code:


try
{
DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();
DocumentBuilder db = dbf.newDocumentBuilder();
docScorm = db.parse(strScorm);

Element root = docScorm.getDocumentElement();
NodeList children = root.getChildNodes();
int n = children.getLength();

String strTopicName = "";
int i = 0 ;
Node genericNode = null ;
Node topicNode = null ;

while(i < n)
{
NodeList topicList = docScorm.getElementsByTagName("title");
genericNode = topicList.item(i);
strTopicName = genericNode.getFirstChild().getNodeValue();

if (strTopicName.equals(strTopic))
{
topicNode = topicList.item(i) ;
}

i++ ;
}

//Save the information in the ScormInfo object.
siItem.setTitle(strTopicName) ;
//We have the topic name - get the other info.
if (topicNode != null)
{
Node itemNode = topicNode.getParentNode() ;
NamedNodeMap nnmItemAtt = itemNode.getAttributes() ;
Node itemIdentifierNode = nnmItemAtt.getNamedItem("identifier") ;
//Fill in the ScormInfo object details.
siItem.setIdentifier(itemIdentifierNode.getFirstChild().getNodeValue()) ;


//I'd given up getting the organisation title, and settled for the identifier attribute instead.
Node orgNode = itemNode.getParentNode() ;
NamedNodeMap nnmOrgAtt = orgNode.getAttributes() ;
Node orgTitleNode = nnmOrgAtt.getNamedItem("identifier") ;
siItem.setOrganisation(orgTitleNode.getFirstChild().getNodeValue()) ;

//Try to get the sibling.
Node preReqNode = topicNode.getNextSibling() ;

...

====================================

And this is the point where it all goes wrong. Can anyone shed some light on what I am doing wrong? Any help would be greatly appreciated.