Update 12/2017: Just use
spring-boot-starter-jetty. For more info refer to the docs.
There could be some advantages in creating standalone web application versus packaging it as WAR and deploying it to container. Avoiding delving into debate, what I can think of is that such application could be easier to deploy/upgrade/restart, especially in situation when there are more web applications living in the container. For example, in case of Jetty, hot-deployment does not always work as expected, causing the need to restart whole thing, which in turn takes time during which applications are offline. Such app is also less prone to possible problems associated with setting up and later upgrading of the container as they come "bundled" with exact flavour they were probably integration-tested with.