For fully-functional examples of manual instrumentation, see Java OpenTelemetry Examples.
Project demonstrating Complete Observability Stack utilizing Prometheus, Loki (For distributed logging), Tempo (For Distributed tracing, this basically uses Jaeger Internally), Grafana for Java/spring based applications (With OpenTelemetry auto / manual Instrumentation) involving multiple microservices with DB interactions
Checkout boot-opentelemetry-tempo and get started
$ mvn clean package docker:build
$ docker-compose up