The generated META-INF/MANIFEST.MF file is used to describe the microservice.
If you open it, you'll see the following:

Main-Class: org.apache.juneau.microservice.RestMicroservice Main-ConfigFile: my-microservice.cfg

The Main-Class entry is the standard manifest entry describing the entry point for the executable jar.
In most cases, this value will always be org.apache.juneau.microservice.RestMicroservice.
However, it is possible to extend this class or implement your own microservice, in which case you'll need to modify this value to point to the new class.

The Main-ConfigFile entry points to the location of an external configuration file for our microservice.

In addition to these predefined manifest entries, you can add your own particular entries to the manifest file and access them through the Manifest API described next.