<dependencies> <dependency> <groupId>com.vaadin</groupId> <artifactId>vaadin-dev-server</artifactId> <version>14.7.3</version> <scope>provided</scope> </dependency> </dependencies> @WebServlet(value = "/*", asyncSupported = true) @VaadinServletConfiguration(productionMode = false, ui = MyUI.class) public static class Servlet extends VaadinServlet { @Override protected void servletInitialized() throws ServletException { super.servletInitialized(); if (VaadinService.getCurrent().getDeploymentConfiguration().isProductionMode()) { DevelopmentModeDetector.debugWindowEnabled = true; } } }