What is an uber jar?

The different names are just ways of packaging java apps.

Skinny – Contains ONLY the bits you literally type into your code editor, and NOTHING else.

Thin – Contains all of the above PLUS the app’s direct dependencies of your app (db drivers, utility libraries, etc).

Hollow – The inverse of Thin – Contains only the bits needed to run your app but does NOT contain the app itself. Basically a pre-packaged “app server” to which you can later deploy your app, in the same style as traditional Java EE app servers, but with important differences.

Fat/Uber – Contains the bit you literally write yourself PLUS the direct dependencies of your app PLUS the bits needed to run your app “on its own”.

Source: Article from Dzone

Reposted from: https://stackoverflow.com/a/57592130/9470346

According to uber-JAR Documentation Approaches: There are three common methods for constructing an uber-JAR:

Unshaded Unpack all JAR files, then repack them into a single JAR. Tools: Maven Assembly Plugin, Classworlds Uberjar

Shaded Same as unshaded, but rename (i.e., "shade") all packages of all dependencies. Tools: Maven Shade Plugin

JAR of JARs The final JAR file contains the other JAR files embedded within. Tools: Eclipse JAR File Exporter, One-JAR.

For Java Developers who use SpringBoot, ÜBER/FAT JAR is normally the final result of the package phase of maven (or build task if you use gradle).

Inside the Fat JAR one can find a META-INF directory inside which the MANIFEST.MF file lives with all the info regarding the Main class. More importantly, at the same level of META-INF directory you find the BOOT-INF directory inside which the directory lib lives and contains all the .jar files that are the dependencies of your application.