4.0.0-M1

org.springframework.lang.Nullable has been replaced by org.jspecify.annotations.Nullable
Spring Boot Admin Client now ships a RestClient autoconfiguration, only
Spring Boot Admin Server still uses RestTemplate (i.e. Notifiers) and all other parts rely on WebClient
Spring Cloud was updated to 2025.1.0
Jolokia does not currently support Spring Boot 4, that's why we downgraded to Jolokia 2.1.0 which, at least, provides some basic functionality (we are currently waiting for version 2.5.0 being released by Jolokia)

spring-boot-admin