Since the inception of the microservices concept, in the Java development community, the paradigm has increasingly shifted toward the fat jar approach. This concept is nothing new, as the first examples of uber jars (a synonym of the fat jar) have been around since the early 2000s, mainly in the desktop development area. The idea around them is pretty simple: instead of using dynamic loading of libraries at runtime, let’s package them all together into an executable jar to simplify the distribution of our application. This is actually the opposite of the model of the application servers, which aim to create an environment as configurable as possible, supporting things such as hot deployment and the hot-swapping of libraries, privileging the uptime to immutability (and predictability).

https://dzone.com/refcardz/introduction-to-cloud-native-java