SpringBoot Issues with RestTemplate Initialization in Spring Cloud Task

I'm currently facing a problem where the RestTemplate isn't being initialized properly when performing a Spring Cloud Task. I’ve tried searching for possible causes but haven't been able to pinpoint the root of the issue.

stacktrace

Caused by: org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'restTemplate' defined in demo.CoreApplication: Failed to instantiate [org.springframework.web.client.RestTemplate]: Illegal factory instance for factory method 'restTemplate'; instance: org.springframework.cloud.task.configuration.observation.ObservationCommandLineRunner
    at org.springframework.beans.factory.support.ConstructorResolver.instantiate(ConstructorResolver.java:648)
    at org.springframework.beans.factory.support.ConstructorResolver.instantiateUsingFactoryMethod(ConstructorResolver.java:485)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.instantiateUsingFactoryMethod(AbstractAutowireCapableBeanFactory.java:1337)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBeanInstance(AbstractAutowireCapableBeanFactory.java:1167)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:562)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:522)
    at org.springframework.beans.factory.support.AbstractBeanFactory.lambda$doGetBean$0(AbstractBeanFactory.java:337)
    at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:234)
    at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:335)
    at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:200)
    at org.springframework.beans.factory.config.DependencyDescriptor.resolveCandidate(DependencyDescriptor.java:254)
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.doResolveDependency(DefaultListableBeanFactory.java:1443)
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.resolveDependency(DefaultListableBeanFactory.java:1353)
    at org.springframework.beans.factory.support.ConstructorResolver.resolveAutowiredArgument(ConstructorResolver.java:904)
    at org.springframework.beans.factory.support.ConstructorResolver.createArgumentArray(ConstructorResolver.java:782)
    ... 74 common frames omitted
Caused by: org.springframework.beans.BeanInstantiationException: Failed to instantiate [org.springframework.web.client.RestTemplate]: Illegal factory instance for factory method 'restTemplate'; instance: org.springframework.cloud.task.configuration.observation.ObservationCommandLineRunner
    at org.springframework.beans.factory.support.SimpleInstantiationStrategy.instantiate(SimpleInstantiationStrategy.java:159)
    at org.springframework.beans.factory.support.ConstructorResolver.instantiate(ConstructorResolver.java:644)
    ... 88 common frames omitted
Caused by: java.lang.IllegalArgumentException: object is not an instance of declaring class
    at java.base/jdk.internal.reflect.DirectMethodHandleAccessor.checkReceiver(DirectMethodHandleAccessor.java:197)
    at java.base/jdk.internal.reflect.DirectMethodHandleAccessor.invoke(DirectMethodHandleAccessor.java:99)
    at java.base/java.lang.reflect.Method.invoke(Method.java:580)
    at org.springframework.beans.factory.support.SimpleInstantiationStrategy.instantiate(SimpleInstantiationStrategy.java:140)
    ... 89 common frames omitted

I'm using the following versions in my setup:

Java21
Spring Boot 3.2.7
spring-cloud-starter-task:3.1.1

Comment From: bclozel

This issue is not really actionable from our side as there is no way for us to reproduce it.

Could you first create an issue in spring cloud task with a minimal sample application that reproduces the problem? We can then reconsider this issue if it turns out to be a Spring Boot problem.

Thanks.