What is a Fat JAR?

A Fat JAR is an executable JAR file in Java that contains not only the compiled application code but also all necessary dependencies (libraries) within a single archive. This simplifies distribution and execution of the application, as there is no need to manage external libraries separately.

Advantages of Fat JAR:

• Deployment convenience: only one file is needed.
• Dependency isolation: no conflicts with other library versions.

Disadvantages:

• The file size is significantly larger than a regular JAR.
• When updating a library, the entire JAR needs to be rebuilt.

An example of creating a Fat JAR using the Maven plugin maven-shade-plugin allows bundling all dependencies into one file.