Pourquoi un simple exemple de démarrage/intégration de Spring cause-t-il que "Le bean demandé est actuellement en cours de création"?

Question

J'ai un exemple assez minime, qui provoque une erreur. Notez que les paquets semblent importer, en mettant toutes les classes dans le même paquet fonctionne.

Fondamentalement, je crée un DirectChannel, j'ai un @Component qui est automatiquement câblé avec lui, et un ServiceActivator dans la @Configuration qui fait référence au même canal. Pour autant que je sache, je ne fais rien de spécial ou d'inhabituel, alors peut-être que c'est un bug?

exemple de code complet en dessous, prêter attention aux paquets ('test' et 'test.config')

Merci!

pom.xml

<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 
    xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd"> 
    <modelVersion>4.0.0</modelVersion> 

    <parent> 
     <groupId>org.springframework.boot</groupId> 
     <artifactId>spring-boot-starter-parent</artifactId> 
     <version>1.5.7.RELEASE</version> 
    </parent> 

    <groupId>my.test</groupId> 
    <artifactId>Circularity</artifactId> 
    <version>0.0.1-SNAPSHOT</version> 

    <properties> 
     <java.version>1.8</java.version> 
    </properties> 

    <dependencies> 
     <!-- Spring boot integration starter --> 
     <dependency> 
      <groupId>org.springframework.boot</groupId> 
      <artifactId>spring-boot-starter-integration</artifactId> 
     </dependency> 
    </dependencies> 

    <build> 
     <plugins> 
      <!-- Package as an executable jar --> 
      <plugin> 
       <groupId>org.springframework.boot</groupId> 
       <artifactId>spring-boot-maven-plugin</artifactId> 
      </plugin> 
     </plugins> 
    </build> 
</project> 

IntegrationConfiguration.java

package test; 

import org.springframework.context.annotation.Bean; 
import org.springframework.context.annotation.Configuration; 
import org.springframework.integration.annotation.ServiceActivator; 
import org.springframework.integration.channel.DirectChannel; 
import org.springframework.messaging.MessageHandler; 

@Configuration 
public class IntegrationConfiguration { 

    @Bean 
    DirectChannel myChannel() { 

     return new DirectChannel(); 
    } 

    @Bean 
    @ServiceActivator(inputChannel = "myChannel") 
    public MessageHandler stdoutMessageHandler() { 

     return m -> System.out.println(m.toString()); 
    } 

} 

SomeComponent.java

package test.config; 

import org.springframework.beans.factory.annotation.Autowired; 
import org.springframework.messaging.MessageChannel; 
import org.springframework.stereotype.Component; 

@Component 
public class SomeComponent { 

    @Autowired 
    public SomeComponent(MessageChannel myChannel) { 
     // Pretend I store the MessageChannel so I can send something to it later. 
     // But this is not needed to cause the issue! 
    } 

} 

CircularApp.java

package test; 

import org.springframework.boot.SpringApplication; 
import org.springframework.boot.autoconfigure.SpringBootApplication; 

@SpringBootApplication 
public class CircularApp { 

    public static void main(String[] args) { 

     SpringApplication.run(CircularApp.class, args); 
    } 
} 

Et sur la demande populaire, une trace de la pile :) Notez que c'est sur une autre machine, avec le code de cette question rapidement copié collé.

. ____   _   __ _ _ 
/\\/___'_ __ _ _(_)_ __ __ _ \ \ \ \ 
(()\___ | '_ | '_| | '_ \/ _` | \ \ \ \ 
\\/ ___)| |_)| | | | | || (_| | )))) 
    ' |____| .__|_| |_|_| |_\__, |//// 
=========|_|==============|___/=/_/_/_/ 
:: Spring Boot ::  (v1.5.7.RELEASE) 

2017-10-10 20:14:26.537 INFO 1796 --- [   main] test.CircularApp       : Starting CircularApp on ORCA with PID 1796 (C:\Storage\workspace\Circularity\target\classes started by Jeroen in C:\Storage\workspace\Circularity) 
2017-10-10 20:14:26.539 INFO 1796 --- [   main] test.CircularApp       : No active profile set, falling back to default profiles: default 
2017-10-10 20:14:26.578 INFO 1796 --- [   main] s.c.a.AnnotationConfigApplicationContext : Refreshing org.springframework.context.annotation.AnnotationConfigApplicationContext@7dc222ae: startup date [Tue Oct 10 20:14:26 CEST 2017]; root of context hierarchy 
2017-10-10 20:14:26.790 INFO 1796 --- [   main] o.s.i.config.IntegrationRegistrar  : No bean named 'integrationHeaderChannelRegistry' has been explicitly defined. Therefore, a default DefaultHeaderChannelRegistry will be created. 
2017-10-10 20:14:26.877 INFO 1796 --- [   main] faultConfiguringBeanFactoryPostProcessor : No bean named 'errorChannel' has been explicitly defined. Therefore, a default PublishSubscribeChannel will be created. 
2017-10-10 20:14:26.879 INFO 1796 --- [   main] faultConfiguringBeanFactoryPostProcessor : No bean named 'taskScheduler' has been explicitly defined. Therefore, a default ThreadPoolTaskScheduler will be created. 
2017-10-10 20:14:26.960 INFO 1796 --- [   main] trationDelegate$BeanPostProcessorChecker : Bean 'integrationGlobalProperties' of type [org.springframework.beans.factory.config.PropertiesFactoryBean] is not eligible for getting processed by all BeanPostProcessors (for example: not eligible for auto-proxying) 
2017-10-10 20:14:26.963 INFO 1796 --- [   main] trationDelegate$BeanPostProcessorChecker : Bean 'integrationGlobalProperties' of type [java.util.Properties] is not eligible for getting processed by all BeanPostProcessors (for example: not eligible for auto-proxying) 
2017-10-10 20:14:27.028 WARN 1796 --- [   main] s.c.a.AnnotationConfigApplicationContext : Exception encountered during context initialization - cancelling refresh attempt: org.springframework.beans.factory.UnsatisfiedDependencyException: Error creating bean with name 'someComponent' defined in file [C:\Storage\workspace\Circularity\target\classes\test\config\SomeComponent.class]: Unsatisfied dependency expressed through constructor parameter 0; nested exception is org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'integrationConfiguration' defined in file [C:\Storage\workspace\Circularity\target\classes\test\IntegrationConfiguration.class]: Initialization of bean failed; nested exception is org.springframework.messaging.core.DestinationResolutionException: A bean definition with name 'myChannel' exists, but failed to be created; nested exception is org.springframework.beans.factory.BeanCurrentlyInCreationException: Error creating bean with name 'myChannel': Requested bean is currently in creation: Is there an unresolvable circular reference? 
2017-10-10 20:14:27.034 INFO 1796 --- [   main] utoConfigurationReportLoggingInitializer : 

Error starting ApplicationContext. To display the auto-configuration report re-run your application with 'debug' enabled. 
2017-10-10 20:14:27.039 ERROR 1796 --- [   main] o.s.boot.SpringApplication    : Application startup failed 

org.springframework.beans.factory.UnsatisfiedDependencyException: Error creating bean with name 'someComponent' defined in file [C:\Storage\workspace\Circularity\target\classes\test\config\SomeComponent.class]: Unsatisfied dependency expressed through constructor parameter 0; nested exception is org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'integrationConfiguration' defined in file [C:\Storage\workspace\Circularity\target\classes\test\IntegrationConfiguration.class]: Initialization of bean failed; nested exception is org.springframework.messaging.core.DestinationResolutionException: A bean definition with name 'myChannel' exists, but failed to be created; nested exception is org.springframework.beans.factory.BeanCurrentlyInCreationException: Error creating bean with name 'myChannel': Requested bean is currently in creation: Is there an unresolvable circular reference? 
    at org.springframework.beans.factory.support.ConstructorResolver.createArgumentArray(ConstructorResolver.java:749) ~[spring-beans-4.3.11.RELEASE.jar:4.3.11.RELEASE] 
    at org.springframework.beans.factory.support.ConstructorResolver.autowireConstructor(ConstructorResolver.java:189) ~[spring-beans-4.3.11.RELEASE.jar:4.3.11.RELEASE] 
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.autowireConstructor(AbstractAutowireCapableBeanFactory.java:1193) ~[spring-beans-4.3.11.RELEASE.jar:4.3.11.RELEASE] 
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBeanInstance(AbstractAutowireCapableBeanFactory.java:1095) ~[spring-beans-4.3.11.RELEASE.jar:4.3.11.RELEASE] 
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:513) ~[spring-beans-4.3.11.RELEASE.jar:4.3.11.RELEASE] 
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:483) ~[spring-beans-4.3.11.RELEASE.jar:4.3.11.RELEASE] 
    at org.springframework.beans.factory.support.AbstractBeanFactory$1.getObject(AbstractBeanFactory.java:306) ~[spring-beans-4.3.11.RELEASE.jar:4.3.11.RELEASE] 
    at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:230) ~[spring-beans-4.3.11.RELEASE.jar:4.3.11.RELEASE] 
    at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:302) ~[spring-beans-4.3.11.RELEASE.jar:4.3.11.RELEASE] 
    at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:197) ~[spring-beans-4.3.11.RELEASE.jar:4.3.11.RELEASE] 
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.preInstantiateSingletons(DefaultListableBeanFactory.java:761) ~[spring-beans-4.3.11.RELEASE.jar:4.3.11.RELEASE] 
    at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:867) ~[spring-context-4.3.11.RELEASE.jar:4.3.11.RELEASE] 
    at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:543) ~[spring-context-4.3.11.RELEASE.jar:4.3.11.RELEASE] 
    at org.springframework.boot.SpringApplication.refresh(SpringApplication.java:693) [spring-boot-1.5.7.RELEASE.jar:1.5.7.RELEASE] 
    at org.springframework.boot.SpringApplication.refreshContext(SpringApplication.java:360) [spring-boot-1.5.7.RELEASE.jar:1.5.7.RELEASE] 
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:303) [spring-boot-1.5.7.RELEASE.jar:1.5.7.RELEASE] 
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:1118) [spring-boot-1.5.7.RELEASE.jar:1.5.7.RELEASE] 
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:1107) [spring-boot-1.5.7.RELEASE.jar:1.5.7.RELEASE] 
    at test.CircularApp.main(CircularApp.java:11) [classes/:na] 
Caused by: org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'integrationConfiguration' defined in file [C:\Storage\workspace\Circularity\target\classes\test\IntegrationConfiguration.class]: Initialization of bean failed; nested exception is org.springframework.messaging.core.DestinationResolutionException: A bean definition with name 'myChannel' exists, but failed to be created; nested exception is org.springframework.beans.factory.BeanCurrentlyInCreationException: Error creating bean with name 'myChannel': Requested bean is currently in creation: Is there an unresolvable circular reference? 
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:564) ~[spring-beans-4.3.11.RELEASE.jar:4.3.11.RELEASE] 
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:483) ~[spring-beans-4.3.11.RELEASE.jar:4.3.11.RELEASE] 
    at org.springframework.beans.factory.support.AbstractBeanFactory$1.getObject(AbstractBeanFactory.java:306) ~[spring-beans-4.3.11.RELEASE.jar:4.3.11.RELEASE] 
    at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:230) ~[spring-beans-4.3.11.RELEASE.jar:4.3.11.RELEASE] 
    at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:302) ~[spring-beans-4.3.11.RELEASE.jar:4.3.11.RELEASE] 
    at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:197) ~[spring-beans-4.3.11.RELEASE.jar:4.3.11.RELEASE] 
    at org.springframework.beans.factory.support.ConstructorResolver.instantiateUsingFactoryMethod(ConstructorResolver.java:372) ~[spring-beans-4.3.11.RELEASE.jar:4.3.11.RELEASE] 
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.instantiateUsingFactoryMethod(AbstractAutowireCapableBeanFactory.java:1173) ~[spring-beans-4.3.11.RELEASE.jar:4.3.11.RELEASE] 
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBeanInstance(AbstractAutowireCapableBeanFactory.java:1067) ~[spring-beans-4.3.11.RELEASE.jar:4.3.11.RELEASE] 
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:513) ~[spring-beans-4.3.11.RELEASE.jar:4.3.11.RELEASE] 
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:483) ~[spring-beans-4.3.11.RELEASE.jar:4.3.11.RELEASE] 
    at org.springframework.beans.factory.support.AbstractBeanFactory$1.getObject(AbstractBeanFactory.java:306) ~[spring-beans-4.3.11.RELEASE.jar:4.3.11.RELEASE] 
    at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:230) ~[spring-beans-4.3.11.RELEASE.jar:4.3.11.RELEASE] 
    at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:302) ~[spring-beans-4.3.11.RELEASE.jar:4.3.11.RELEASE] 
    at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:202) ~[spring-beans-4.3.11.RELEASE.jar:4.3.11.RELEASE] 
    at org.springframework.beans.factory.config.DependencyDescriptor.resolveCandidate(DependencyDescriptor.java:208) ~[spring-beans-4.3.11.RELEASE.jar:4.3.11.RELEASE] 
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.doResolveDependency(DefaultListableBeanFactory.java:1138) ~[spring-beans-4.3.11.RELEASE.jar:4.3.11.RELEASE] 
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.resolveDependency(DefaultListableBeanFactory.java:1066) ~[spring-beans-4.3.11.RELEASE.jar:4.3.11.RELEASE] 
    at org.springframework.beans.factory.support.ConstructorResolver.resolveAutowiredArgument(ConstructorResolver.java:835) ~[spring-beans-4.3.11.RELEASE.jar:4.3.11.RELEASE] 
    at org.springframework.beans.factory.support.ConstructorResolver.createArgumentArray(ConstructorResolver.java:741) ~[spring-beans-4.3.11.RELEASE.jar:4.3.11.RELEASE] 
    ... 18 common frames omitted 
Caused by: org.springframework.messaging.core.DestinationResolutionException: A bean definition with name 'myChannel' exists, but failed to be created; nested exception is org.springframework.beans.factory.BeanCurrentlyInCreationException: Error creating bean with name 'myChannel': Requested bean is currently in creation: Is there an unresolvable circular reference? 
    at org.springframework.integration.support.channel.BeanFactoryChannelResolver.resolveDestination(BeanFactoryChannelResolver.java:93) ~[spring-integration-core-4.3.12.RELEASE.jar:4.3.12.RELEASE] 
    at org.springframework.integration.support.channel.BeanFactoryChannelResolver.resolveDestination(BeanFactoryChannelResolver.java:46) ~[spring-integration-core-4.3.12.RELEASE.jar:4.3.12.RELEASE] 
    at org.springframework.integration.config.annotation.AbstractMethodAnnotationPostProcessor.createEndpoint(AbstractMethodAnnotationPostProcessor.java:290) ~[spring-integration-core-4.3.12.RELEASE.jar:4.3.12.RELEASE] 
    at org.springframework.integration.config.annotation.AbstractMethodAnnotationPostProcessor.postProcess(AbstractMethodAnnotationPostProcessor.java:220) ~[spring-integration-core-4.3.12.RELEASE.jar:4.3.12.RELEASE] 
    at org.springframework.integration.config.annotation.MessagingAnnotationPostProcessor.processAnnotationTypeOnMethod(MessagingAnnotationPostProcessor.java:228) ~[spring-integration-core-4.3.12.RELEASE.jar:4.3.12.RELEASE] 
    at org.springframework.integration.config.annotation.MessagingAnnotationPostProcessor$1.doWith(MessagingAnnotationPostProcessor.java:200) ~[spring-integration-core-4.3.12.RELEASE.jar:4.3.12.RELEASE] 
    at org.springframework.util.ReflectionUtils.doWithMethods(ReflectionUtils.java:530) ~[spring-core-4.3.11.RELEASE.jar:4.3.11.RELEASE] 
    at org.springframework.util.ReflectionUtils.doWithMethods(ReflectionUtils.java:537) ~[spring-core-4.3.11.RELEASE.jar:4.3.11.RELEASE] 
    at org.springframework.integration.config.annotation.MessagingAnnotationPostProcessor.postProcessAfterInitialization(MessagingAnnotationPostProcessor.java:180) ~[spring-integration-core-4.3.12.RELEASE.jar:4.3.12.RELEASE] 
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.applyBeanPostProcessorsAfterInitialization(AbstractAutowireCapableBeanFactory.java:423) ~[spring-beans-4.3.11.RELEASE.jar:4.3.11.RELEASE] 
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.initializeBean(AbstractAutowireCapableBeanFactory.java:1633) ~[spring-beans-4.3.11.RELEASE.jar:4.3.11.RELEASE] 
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:555) ~[spring-beans-4.3.11.RELEASE.jar:4.3.11.RELEASE] 
    ... 37 common frames omitted 
Caused by: org.springframework.beans.factory.BeanCurrentlyInCreationException: Error creating bean with name 'myChannel': Requested bean is currently in creation: Is there an unresolvable circular reference? 
    at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.beforeSingletonCreation(DefaultSingletonBeanRegistry.java:347) ~[spring-beans-4.3.11.RELEASE.jar:4.3.11.RELEASE] 
    at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:223) ~[spring-beans-4.3.11.RELEASE.jar:4.3.11.RELEASE] 
    at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:302) ~[spring-beans-4.3.11.RELEASE.jar:4.3.11.RELEASE] 
    at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:202) ~[spring-beans-4.3.11.RELEASE.jar:4.3.11.RELEASE] 
    at org.springframework.integration.support.channel.BeanFactoryChannelResolver.resolveDestination(BeanFactoryChannelResolver.java:89) ~[spring-integration-core-4.3.12.RELEASE.jar:4.3.12.RELEASE] 
    ... 48 common frames omitted 

Answer 1

@Autowired 
public SomeComponent(MessageChannel myChannel) { 
    // Pretend I will send something to the channel. 
} 

Vous ne pouvez pas commencer à envoyer des messages jusqu'à ce que le contexte d'application est entièrement construit; envoyer un message d'un constructeur est évidemment avant cela.