public void init(ServletConfig config) throws ServletException {
super.init(config);
String unit = config.getInitParameter("persistence.unit");
String mock = config.getInitParameter("mock");
String serverTrace = config.getInitParameter("server-side-stacktrace");
_del = ("true".equalsIgnoreCase(mock)) ? new MockTradingService() : new Exchange(unit);
_translator.setPrintServerSideStackTrace("true".equalsIgnoreCase(serverTrace));
}