How does OpenTelemetry Java Agent work ?

[santoshkashyap]

Any good explanation on how exactly is the Agent able to intercept calls to all the support libraries/frameworks listed here.

I see that the main OpenTelemetryJavaAgent.java is implementing Java's Instrumentation API. But, after that does it provide hooks into supported libraries & frameworks(e.g. spring, jdbc and so on) and, “watches” for certain functions to be called or is the final byte code in the JVM already has instrumentation logic from the OpenTelemetry ?