Application Packaging

Spring Boot really is a set of bootstrap libraries with some convention for configurations, but there’s no reason why you couldn’t run a Spring Boot application inside your existing application servers (as a WAR). The idiom that most developers who use Spring Boot prefer is the self-contained JAR packaging for their application. This means Spring Boot packages all dependencies and application code into a self-contained JAR with a flat class loader. This makes it easier to understand application startup, dependency ordering, and log statements; but more importantly, it helps reduce the number of moving pieces required to take an app safely to production. This means you don’t take an app and chuck it into an app server; the app, once it’s built, is ready to run as is—standalone—including embedding its own servlet container if it uses servlets. That’s right, a simple java -jar <name.jar> is enough to start your application now! Spring Boot, Dropwizard, and WildFly Swarm all follow this pattern of packaging everything into an executable uber JAR.

But what about management things we typically expect out of an application server?