xalan-J : possible thread-safety problem in ExsltStrings

[Simon Kitching <si...@ecnetwork.co.nz>]

Hi All,

In class org.apache.xalan.lib.ExsltStrings, a static member of type
"Document" is kept around to be used as a factory for Elements, etc. 

The object is created using the normal expression:
  lDoc =
DocumentBuilderFactory.newInstance().newDocumentBuilder().newDocument().
There is, therefore, no guaruntee that this is a Xerces Document object.

This object is accessed without any locking from the following static
methods:
* split(String str, String pattern)
* tokenize(String toTokenize, String delims)

The methods invoked on the Document object are:
* Element org.w3c.dom.Document.createElement(String)
* Text org.w3c.dom.Document.createTextNode(String)

What this means is that there may be multiple threads simultaneously
invoking the above methods on a single Document object.

Is this safe?

I cannot find any documentation on the subject of the thread-safety of
the Document methods listed above.
If these are not thread-safe, then perhaps a bug should be raised
against ExsltStrings?

In addition, the static member is initialized in a non-thread-safe
manner. However, due to the way the resulting object is used I do not
think that any race condition can result. The worst that can happen is
that multiple Document objects are created, only one of which is then
cached for later use. I think this is probably not worth fixing [though
might be worth adding a comment about].

Regards,

Simon