2. If I understand correctly, the problem is that multiple users are getting the same DOM object?
a. Question: Why do you have two actions that do essentially the same thing? b. By the way, even though you declared them ThreadSafe they clearly are not. It is possible for the web-browser to issue two requests at the same time to Cocoon for the same user, depending on how the html page is constructed, in which case both of these actions could execute at the same time.
c. What is the purpose of synchronizing the object returned by newInstance? That is a local variable and if each call to newInstance returns a different object, this will accomplish nothing. If you want to serialize the call to newDocument then you should refactor this whole block of code in a method in a utility class and then always call that method from all your actions to get the document. It should do something like:
private static final String LOCK = "Lock";
Document getDocument()
{
Request request = ObjectModelHelper.getRequest(objectModel);
Session session = request.getSession(true);
Document doc = (Document)session.getAttribute("myAttribute");
if (doc == null)
{
// It is possible for more than one thread to get here at the same time with doc == null
syncronize(LOCK);
{ // So check again. Only the first caller should actually create the document.
doc = (Document)session.getAttribute("myAttribute");
if (doc == null)
{ DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance(); doc = dbf.newDocumentBuilder().newDocument();
session.setAttribute("myAttribute", doc);
} }
}
return doc;
}
