java - JAR vs WAR file specification

Question

I noticed that WAR files are supposed to have classes/ and lib/ directories for containing their classfile root and dependencies, respectively.

I also noticed that it is not common practice for JARs to contain such a lib/ directory and to contain their own dependencies.

So now I'm wondering why JARs shouldn't/usually-don't contain their own dependencies, but WAR files are expected to. Unless I'm missing something, both require their dependencies to be on the classpath at runtime (JARs won't run if they're missing dependencies, just like WARs won't run). So to me, all the arguments for putting dependencies in a WAR file also apply to a JAR.

What am I not "getting" here?!?

Answer 1

From a conceptual point of view:
A jar typically represents a single library which can be used and may or may not have dependencies.
But the idea is that a specific functionality can be provided as a library in a jar.

A war is an application by itself and as such it should include all the dependencies