Q2.deployElement doesn't write the destination file atomically, which can make the deploy polling to fail

[alcarraz]

In Q2.deployElement we create the file directly in the deploy directory. I believe this may be causing what's reported in this stack overflow question.

Maybe we should do the same that is advised, of writing the file in a temporary file, maybe with a .tmp extension, and then move it to the final deploy name?

jPOS/jpos/src/main/java/org/jpos/q2/Q2.java

Lines 813 to 832 in f047169

	public void deployElement (Element e, String fileName, boolean encrypt, boolean isTransient)
	throws ISOException, IOException, GeneralSecurityException
	{
	e = e.clone ();
	XMLOutputter out = new XMLOutputter (Format.getPrettyFormat());
	Document doc = new Document ();
	doc.setRootElement(e);
	File qbean = new File (deployDir, fileName);
	if (isTransient) {
	e.setAttribute("instance", getInstanceId().toString());
	qbean.deleteOnExit();
	}
	if (encrypt) {
	doc = encrypt (doc);
	}
	try (Writer writer = new BufferedWriter(new FileWriter(qbean))) {
	out.output(doc, writer);
	}
	}

[alcarraz]

If agreed, I can implement the PR.

[ar]

We can approach this in two ways:

Initiate the file with a .tmp extension and subsequently rename it. However, potential challenges could arise with Windows' move or when deploying to a FUSE file system.

Implement an internal Semaphore, given this is a Q2 method. While this seems more streamlined initially, it could pose issues if multiple Q2s utilize the same deploy. This scenario, albeit unusual, is still possible.

Both methods come with their respective advantages and limitations.