WAR Packaging in Spring Boot

You'd choose WAR packaging when you need to deploy to an external servlet container that's already installed and managed by your operations team. This is still really common in enterprise environments. For example, a bank might have a centralized WebSphere or JBoss installation where all internal applications run. The ops team manages that server infrastructure, handles security patches, and monitors everything through one console. In that scenario, they want you to provide a WAR file that they drop into their managed environment. It's about centralized control. Modern cloud deployments prefer JAR packaging because it's self-contained. Your application brings its own embedded Tomcat, so you control the full stack. You can version independently, deploy to Kubernetes easily, and don't depend on someone else's server infrastructure. But it's wrong to think WAR is dead. In regulated industries like finance or healthcare, there are often compliance requirements or governance policies that mandate application server deployments. The operations team might need to demonstrate that all applications use a patched, approved version of Tomcat, which is easier with centralized deployment. One thing that's cool about Spring Boot is you can actually create a dual-mode WAR. You change your packaging to WAR in pom.xml, extend SpringBootServletInitializer in your main class, and the resulting WAR can work both ways. You can deploy it to external Tomcat, or you can run it directly with java -jar like an executable JAR. This gives you flexibility if you're not sure which model you'll need. A common mistake freshers make is assuming WAR is purely legacy and dismissing it. When you join an enterprise with existing infrastructure, you might find that WAR deployment is the standard, and you need to work within that model. The key is understanding when each approach makes sense based on your deployment environment and operational requirements.