code: protected final File createTempDir(String prefix) {
  		try {
  			File tempDir = File.createTempFile(prefix + ".", "." + getPort());
  			tempDir.delete();
  			tempDir.mkdir();
  			tempDir.deleteOnExit();
  			return tempDir;
  		}
  		catch (IOException ex) {
  			throw new WebServerException(
  					"Unable to create tempDir. java.io.tmpdir is set to "
  							+ System.getProperty("java.io.tmpdir"),
  					ex);
  		}
  	}
docs: Return the absolute temp dir for given web server.
  @param prefix server name
  @return the temp dir for given server.