String subMessage = "";
String colStr = req.getParameter(PARAM_PLAY_KEY);
if (colStr != null) {
try {
int colIdx = Integer.parseInt(colStr);
game.dropDisc(colIdx - 1);
} catch (NumberFormatException e) {
subMessage = "Invalid parameter col: " + colStr;
log.error("Invalid column", e);
} catch (ConnectFourException e) {
subMessage = e.getMessage();