Spring Cloud Openfeign Dependency Cycle reported when an ApplicationListener depends on a Feign client

Describe the bug I have an application where a bean that implements ApplicationListener<ApplicationContextEvent> depends on a feign client. The application fails to start because Spring thinks there is a dependency cycle. Debugging shows that this is due to AbstractApplicationContext.refresh() being called during creation of the feign client bean.

spring-cloud version is Hoxton.SR1, spring-boot version is 2.2.4.RELEASE.

Sample Here's a simple application that shows the problem. I created a Kotlin app using Spring Initalizr with only OpenFeign selected as a dependency, then changed the DemoApplication.kt as follows:

package com.example.demo

import org.springframework.boot.autoconfigure.SpringBootApplication
import org.springframework.boot.runApplication
import org.springframework.cloud.openfeign.EnableFeignClients
import org.springframework.cloud.openfeign.FeignClient
import org.springframework.context.ApplicationListener
import org.springframework.context.annotation.Configuration
import org.springframework.context.event.ApplicationContextEvent
import org.springframework.web.bind.annotation.RequestMapping
import org.springframework.web.bind.annotation.RequestMethod

@SpringBootApplication
@EnableFeignClients
class DemoApplication

fun main(args: Array<String>) {
    runApplication<DemoApplication>(*args)
}

@FeignClient(name = "myFeignClient")
interface MyFeignClient {
    @RequestMapping(method = [RequestMethod.POST])
    fun hello(): String
}

@Configuration
class MyApplicationListener(private val myFeignClient: MyFeignClient) : ApplicationListener<ApplicationContextEvent> {
    override fun onApplicationEvent(event: ApplicationContextEvent) {
        println("ApplicationEvent: $event")
    }
}

The application fails to start, saying:

2020-02-03 15:21:38.365  WARN 81421 --- [           main] s.c.a.AnnotationConfigApplicationContext : Exception encountered during context initialization - cancelling refresh attempt: org.springframework.beans.factory.BeanCurrentlyInCreationException: Error creating bean with name 'myApplicationListener': Requested bean is currently in creation: Is there an unresolvable circular reference?
2020-02-03 15:22:02.452  WARN 81421 --- [           main] s.c.a.AnnotationConfigApplicationContext : Exception encountered during context initialization - cancelling refresh attempt: org.springframework.beans.factory.UnsatisfiedDependencyException: Error creating bean with name 'myApplicationListener' defined in file [.../target/classes/com/example/demo/MyApplicationListener.class]: Unsatisfied dependency expressed through constructor parameter 0; nested exception is org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'com.example.demo.MyFeignClient': FactoryBean threw exception on object creation; nested exception is org.springframework.beans.factory.BeanCurrentlyInCreationException: Error creating bean with name 'myApplicationListener': Requested bean is currently in creation: Is there an unresolvable circular reference?
2020-02-03 15:22:02.464  INFO 81421 --- [           main] ConditionEvaluationReportLoggingListener : 

Error starting ApplicationContext. To display the conditions report re-run your application with 'debug' enabled.
2020-02-03 15:22:02.480 ERROR 81421 --- [           main] o.s.b.d.LoggingFailureAnalysisReporter   : 

***************************
APPLICATION FAILED TO START
***************************

Description:

The dependencies of some of the beans in the application context form a cycle:

┌─────┐
|  myApplicationListener defined in file [.../target/classes/com/example/demo/MyApplicationListener.class]
↑     ↓
|  com.example.demo.MyFeignClient
└─────┘

Comment From: spencergibb

Inject an ObjectProvider<MyFeignClient>

Comment From: lbilger

Ah, I see this is in the docs of the latest Snapshot but not yet in the GA docs. Thanks!

I had tried adding the @Lazy annotation to the client, but that didn't work. Now I see that adding @Lazy to the injection point works as well - i guess it does more or less the same as using an ObjectProvider but hides it behind a proxy.

Comment From: wylswz

Why does ObjectProvider resolve this issue?

Comment From: lbilger

It breaks up the dependency cycle, you could say. Using ObjectProvider or the Lazy annotation will give Spring a chance to initialize the object only when it‘s used, not when it’s injected.

Comment From: wylswz

it looks like feign client depends on ApplicationListerners, but I cannot find that declaration