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<a class="user-hover" rel="putmanb@shibboleth.net" id="email_putmanb@shibboleth.net" href="https://issues.shibboleth.net/jira/secure/ViewProfile.jspa?name=putmanb%40shibboleth.net" style="color:#326ca6;">Brent Putman</a>
commented on <img src="https://issues.shibboleth.net/jira/images/icons/bug.gif" height="16" width="16" border="0" align="absmiddle" alt="Bug"> <a style='color:#326ca6;text-decoration:none;' href='https://issues.shibboleth.net/jira/browse/JXT-87'>JXT-87</a>
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<a style='color:#326ca6;text-decoration:none;' href='https://issues.shibboleth.net/jira/browse/JXT-87'><strong>Code in AbstractSignableXMLObject etc unnecessarily calls NodeList which is thread-unsafe </strong></a>
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<div class="comment-block" style="background-color:#edf5ff;border:1px solid #dddddd;color:#000000;padding:12px;"><p>My understanding of NodeList's behavior is consistent with the reporter, i.e. it's not threadsafe, even for read operations. Straight from Michael Glavassevich:</p>
<p><a href="http://www.mail-archive.com/j-users@xerces.apache.org/msg03417.html" class="external-link">http://www.mail-archive.com/j-users@xerces.apache.org/msg03417.html</a></p>
<p>See especially towards the end of this issue:</p>
<p><a href="https://issues.apache.org/jira/browse/XERCESJ-727" class="external-link">https://issues.apache.org/jira/browse/XERCESJ-727</a></p>
<p>The question is, does it matter for the places where we are using it?</p>
<p>Where it's being used internally in the impl of an XMLObject, I'm not convinced it's a huge issue. XMLObjects are by design not thread-safe. I suppose we could debate whether that assumption about lack of thread-safety extends to the DOM Element that it is caching, especially since the issue also applies to just reading the DOM as opposed to writing.</p>
<p>I'm more concerned about use of NodeList iteration outside of XMLObject's, particularly in helper functions (e.g. XMLHelper and also classes in java-support). There I don't think there is a presumption about concurrent reading of the DOM, so this is probably an issue.</p>
<p>Then there is the efficiency issue. The getNextSibling style of iteration seems reported to be faster, according to some articles, because it doesn't do any of the cache maintenance, it's just traversing a linked list. </p>
<p>So overall, I'm inclined to say we should just go ahead and do this. Only concern is we need to be careful in the refactoring because introducing a bug here would be major. </p></div>
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