I am trying to do the event handling in my springboot(4.2) application and following this example. When I try to Autowired EventPublisher component into my Service, it creates a problem and throws the following exception:

2023-01-30 18:54:15 DEBUG Processing injected element of bean 'positionService': AutowiredFieldElement for com.mycompany.myproject.event.EventPublisher com.mycompany.myproject.service.PositionService.eventPublisher
2023-01-30 18:54:15 WARN Exception encountered during context initialization - cancelling refresh attempt
org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'positionService': Injection of autowired dependencies failed; nested exception is org.springframework.beans.factory.BeanCreationException: Could not autowire field: com.mycompany.myproject.event.EventPublisher com.mycompany.myproject.service.PositionService.eventPublisher; nested exception is org.springframework.beans.factory.NoSuchBeanDefinitionException: No qualifying bean of type [com.mycompany.myproject.event.EventPublisher] found for dependency: expected at least 1 bean which qualifies as autowire candidate for this dependency. Dependency annotations: {@org.springframework.beans.factory.annotation.Autowired(required=true)}
    at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor.postProcessPropertyValues(AutowiredAnnotationBeanPostProcessor.java:334)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.populateBean(AbstractAutowireCapableBeanFactory.java:1214)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:543)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:482)
    at org.springframework.beans.factory.support.AbstractBeanFactory$1.getObject(AbstractBeanFactory.java:305)
    at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:230)
    at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:301)
    at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:196)
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.preInstantiateSingletons(DefaultListableBeanFactory.java:772)
    at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:834)
    at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:537)
    at org.springframework.web.context.ContextLoader.configureAndRefreshWebApplicationContext(ContextLoader.java:403)
    at org.springframework.web.context.ContextLoader.initWebApplicationContext(ContextLoader.java:306)
    at org.springframework.web.context.ContextLoaderListener.contextInitialized(ContextLoaderListener.java:106)
    at org.apache.catalina.core.StandardContext.listenerStart(StandardContext.java:4762)
    at org.apache.catalina.core.StandardContext.startInternal(StandardContext.java:5222)
    at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:183)
    at org.apache.catalina.core.ContainerBase.addChildInternal(ContainerBase.java:726)
    at org.apache.catalina.core.ContainerBase.addChild(ContainerBase.java:698)
    at org.apache.catalina.core.StandardHost.addChild(StandardHost.java:696)
    at org.apache.catalina.startup.HostConfig.deployDescriptor(HostConfig.java:689)
    at org.apache.catalina.startup.HostConfig$DeployDescriptor.run(HostConfig.java:1888)
    at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511)
    at java.util.concurrent.FutureTask.run$$$capture(FutureTask.java:266)
    at java.util.concurrent.FutureTask.run(FutureTask.java)
    at org.apache.tomcat.util.threads.InlineExecutorService.execute(InlineExecutorService.java:75)
    at    Caused by: org.springframework.beans.factory.NoSuchBeanDefinitionException: No qualifying bean of type [com.mycompany.myproject.event.EventPublisher] found for dependency: expected at least 1 bean which qualifies as autowire candidate for this dependency. Dependency annotations: {@org.springframework.beans.factory.annotation.Autowired(required=true)}
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.raiseNoSuchBeanDefinitionException(DefaultListableBeanFactory.java:1326)
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.doResolveDependency(DefaultListableBeanFactory.java:1072)
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.resolveDependency(DefaultListableBeanFactory.java:967)
    at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor$AutowiredFieldElement.inject(AutowiredAnnotationBeanPostProcessor.java:543)
    ... 58 more

Here is my EventPublisher

@Component
public class EventPublisher {
    @Autowired 
    private ApplicationEventPublisher applicationEventPublisher;
 

    public void publishEvent(String message, Integer eventId) {
        applicationEventPublisher.publishEvent(
                new UserEvent(this, message, eventId)
        );
    }
}

Service:

@Service
public class PositionService extends BaseService implements IPositionService {
    private final Logger LOGGER = LoggerFactory.getLogger(this.getClass());

    

    @Autowired
    EventPublisher eventPublisher;

CodePudding user response：

If @Components (incl @Services) are in are not in the same package (or a sub-package) as the class annotated with @SpringBootApplication then the @SpringBootApplication needs a scanBasePackages, eg

@SpringBootApplication(scanBasePackages = {"basepackage1", "basepackage2"}