MQSeries.net :: View topic - Null pointer exception in custom Java node

prasadpav · Posted: Sun May 01, 2005 2:40 am Post subject:

Hi all,
I'm creating java message processing node to
navigate through the message and modify an element if
it exists. And this is on Message Broker V5.0, CSD 02
on windows XP.
The sample XML i'm working on is:

<listofItems>
<Item>
<ItemTypeA>Data 1:Some data in here<\ItemTypeA>
<\Item
<Item>
<ItemTypeB>Data 2:Someother Typedata<\ItemTypeB>
<\Item>
<Item>
<ItemTypeA>Data 3:Some data in here<\ItemTypeA>
<\Item
<Item>
<ItemTypeA>Data 4:Some data in here<\ItemTypeA>
<\Item
<\listofItems>

Idea is to loop through all the repeating elements
<Item> and change the data for all those elements
which has element name as "ItemTypeA". <ItemTypeB>
should be left unchanged. We are using custom Java
node to this because we want to compress the data and
then Base64 encode the content.

I'm having problem in navigating to the next siblings
of <Item>. I tried lot of combinations but no success.
Here is the bit of code i'm doing:

within the evaluate method:

try {

MbMessage newMsg = new
MbMessage(oldAssembly.getMessage());
MbMessageAssembly newAssembly = new
MbMessageAssembly(oldAssembly, newMsg);

MbElement rootElement =
newAssembly.getMessage().getRootElement();

MbElement [] itemElement =
rootElement.getAllElementsByPath("/XML/listofItems//Item");

MbElement sibling = rootElement.getLastChild().getLastChild().getFirstChild().getFirstChild();
MbElement innerElement = rootElement.getFirstElementByPath("/XML/listofItems/Item/ItemTypeA");

for (int i=0; i< itemElement.length; i++)
{
if (innerElement.getName().equals("ItemTypeA")
{
.....<Then do something here>
}
else {
...<do nothing>....
}

sibling = sibling.getNextSibling(); // gives me next <item>
innerElement = sibling.getFirstChild(); //gives me <ItemTypeA> or <ItemTypeB> depending upon which one exists
}

Couple of problems i'm having while trying to execute this code:
1) In the following piece of code sibling is always null, I expected it to go to the next sibling of <Item>. At sibling.getFirstChild() is the point where i'm getting java.null pointer exception.
sibling = sibling.getNextSibling();
innerElement = sibling.getFirstChild();
2) The for loop worked the for the first occurance of the element <Item>, ONLY because I specified as following before for loop:
MbElement innerElement = rootElement.getFirstElementByPath ("/XML/listofItems/Item/ItemTypeA");
This actually must be sibling.getFirstChild(); (or) sibling.getLastChild() (doesn't make a difference for this example, i guess). If I had mentioned this, then i get null pointer exception in the If statement.

I'm debugging by generating system out println to the console.

Can anyone please suggest to make the looping for the repeatable element work and where i was wrong in the above code?? Sorry for this lengthy posting.....if you see this message till here...then you really are a very patient man !!!!!!

Cheers,
Prasad