Ignition was designed to be a powerful industrial application platform, built from the ground up to support extensibility through a modular architecture. In fact, nearly all of the commercial pieces associated with Ignition, such as SQLBridge, Vision, and OPC-UA, are modules built with the same SDK that you have in your hands.
This guide was written primarily for 7.8 and 7.9 module development. There are new features and capabilities added in Ignition 8.0+, and documentation is always ongoing. Be sure to compile against Java 11 and update your artifacts to reference the new APIs.