Details
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Bug
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Status: Open
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Major
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Resolution: Unresolved
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2.9.1
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None
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None
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n/a
Description
SUMMARY:
When a Node object is adopted into a CoreDocumentImpl Document, the top-most Node has its UserData copied from it's owning document into the adopting document, but other child nodes in the node tree below the top-most node do not get their UserData copied over.
SOLUTION:
The likely solution is to have adoptNode() traverse the Node's child tree and copy hashtable UserData entries from the Node's owning document into the adopting document's UserData hashtable.
REPRO STEPS:
In particular, I am trying to add Line Number information to Node objects
in a xerces document. There is a handy xerces sample application that
shows me how to do this, you can find the sample in
Xerces-J-src.2.9.1.zip:xerces-2_9_1\samples\dom\DOMAddLines.java.
This sample is great! It got me started in the right direction and works
perfectly as long as you are not trying to clone nodes or adopt them to
other documents with the expectation that your line numbers will stick.
The first problem is that the sample does not provide a UserDataHandler
when it calls setUserData(), so I changed my sample around to include my
own handler:
public class DOMLineNumberUserDataHandler implements UserDataHandler
{
public void handle(short operation, String key, Object data, Node src,
Node dst)
{
System.out.println("\nDOMLineNumberUserDataHandler Called: operation="
+ operation + ", key=" +
key + ", data=" + data + ", src=" + src + ", dst=" + dst);
if (operation == UserDataHandler.NODE_ADOPTED)
{ System.out.println("(Current Operation is NODE_ADOPTED)"); }if (dst != null)
{ dst.setUserData(key, data, this); }}
}
That's my handler code, then the sample needed to be changed around, I
added a private UserDataHandler like so at the top of the DOMAddLines:
private UserDataHandler userDataHandler = new DOMLineNumberUserDataHandler();
Then I changed the two lines from this:
node.setUserData("startLine", String.valueOf(locator.getLineNumber()), null);
to this:
node.setUserData("startLine", String.valueOf(locator.getLineNumber()),
this.userDataHandler);
Those two lines are in the DOMAddLines "startDocument" and "startElement"
methods.
With my handler in place, cloning nodes works beautifully.
However, adopting nodes from one document to another does not work.
Here is a brief test case that exemplifies the behaviour I am seeing:
public void testLineNumberStuff()
{
try
catch (Exception e)
{ System.out.println("Caught exception: " + e.getMessage()); e.printStackTrace(); }}
The output of this test case is:
ORIGINAL DOCUMENT BEFORE ADOPTION:
content4:<no></no>3:<with></with>2:<document></document>1:<some></some>
ADOPTING DOCUMENT BEFORE ADOPTION:
document2:<other></other>1:<some></some>
DOMLineNumberUserDataHandler Called: operation=5, key=startLine, data=1,
src=[some: null], dst=null
(Current Operation is NODE_ADOPTED)
ORIGINAL DOCUMENT AFTER ADOPTION:
contentnull:<no></no>null:<with></with>null:<document></document>1:<some></some>
ADOPTING DOCUMENT AFTER ADOPTION:
document2:<other></other>1:<some></some>
As you can see, all of the line number UserData objects except one are
dropped during the adoptNode scenario. All of the numbers in the "ORIGINAL
DOCUMENT" are replaced with nulls except for the "1" that is the UserData
on the top-most node in our example DOM tree.
ADDITIONAL DETAILS
For additional details see this thread on the xerces-J-users mailing list:
Thread title "Help with adoptNode() and setUserData() data being dropped?"