Primefaces p:fileUpload - do something on beginning and end of upload (multiple files) - file-upload

Question

Primefaces 4.0 has nice component to upload files, including multiple files at once. By some dark miracle, it actually works.
Code:
<p:fileUpload fileUploadListener="#{someBean.handleSingleFileUpload}"
mode="advanced" multiple="true" auto="true" dragDropSupport="true"
update=":form_info" sizeLimit="100000" allowTypes="/(\.|\/)(xml)$/" />
Problem is that listener someBean.handleSingleFileUpload is called once for each file. I dealt with that nicely, but I cannot see any way to execute some code at beginning and on end of entire upload process. IMO rather large oversight.
For example:
at beginning clear info textarea
now multiple files are uploaded simultaneously...
at end reload something based on data that was just uploaded
Of course, things at beginning and end should be executed only once, regardless of amount of files. Is there any way to do that? In primefaces docs for p:fileUpload there are no other attribute calling bean method than fileUploadListener.

Answer 1

Well, I ended up simply using counter. Obvious in hindsight, eh. Example:
private int eventCounter = 0;
public void handleSingleFileUpload(FileUploadEvent event)
{
beginImport();
try
{
// code to import file, for example parse xml
} catch (Exception ex)
{
ex.printStackTrace(); /// or whatever
} // block catch Exception
finally
{
finishImport();
} // block finally
}
private synchronized void beginImport()
{
if (eventCounter == 0)
{
// insert code to execute before first file is started
} // block if just started
eventCounter++;
}
private synchronized void finishImport()
{
eventCounter--;
if (eventCounter < 0) eventCounter = 0; // Just in case...
if (eventCounter > 0) return; // not really finished yet
// insert code to execute when last file is done
}
It is hackish solution and I fear that in some cases it could call begin-n-finish pair twice (it should not do begin or finish code twice in row) and that could theoretically interfere with ongoing import of n-th file.
It works for me, at least for now. Will see how it holds when xml will have thousands or more of entries instead of dozen. I would prefer something like onStartOfEverything and onEndOfEverything as arguments in p:fileUpload tag, but ah well.