在Spring MVC中，无法从单独的服务包中找到bean

Question

我得到的错误是NoSuchBeanDefinitionException，我有一个web应用程序，我目前正在开发它来集成一些DB功能。我的结构低于

domain.mainpackage
+ControllerClass
+SomeOtherClass
domain.DAOpackage
+someDAOClass
+someDAOimpl
domain.service
+MainService
+MainServiceImpl

我遇到的问题是，Controller在构建应用程序时找不到MainServiceClass的bean(见下面的错误(

Nov 22, 2018 11:43:01 AM org.apache.catalina.core.ApplicationContext log
SEVERE: StandardWrapper.Throwable
org.springframework.beans.factory.UnsatisfiedDependencyException: Error creating bean with name 'applicationController': Unsatisfied dependency expressed through field 'mainService'; nested exception is org.springframework.beans.factory.NoSuchBeanDefinitionException: No qualifying bean of type 'domain.service.MainService' available: expected at least 1 bean which qualifies as autowire candidate. Dependency annotations: {@org.springframework.beans.factory.annotation.Autowired(required=true)}
at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor$AutowiredFieldElement.inject(AutowiredAnnotationBeanPostProcessor.java:588)
at org.springframework.beans.factory.annotation.InjectionMetadata.inject(InjectionMetadata.java:88)
at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor.postProcessPropertyValues(AutowiredAnnotationBeanPostProcessor.java:366)
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.populateBean(AbstractAutowireCapableBeanFactory.java:1272)
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:553)
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:483)
at org.springframework.beans.factory.support.AbstractBeanFactory$1.getObject(AbstractBeanFactory.java:312)
at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:230)
at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:308)
at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:197)
at org.springframework.beans.factory.support.DefaultListableBeanFactory.preInstantiateSingletons(DefaultListableBeanFactory.java:761)
at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:867)
at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:543)
at org.springframework.web.servlet.FrameworkServlet.configureAndRefreshWebApplicationContext(FrameworkServlet.java:668)
at org.springframework.web.servlet.FrameworkServlet.createWebApplicationContext(FrameworkServlet.java:634)
at org.springframework.web.servlet.FrameworkServlet.createWebApplicationContext(FrameworkServlet.java:682)
at org.springframework.web.servlet.FrameworkServlet.initWebApplicationContext(FrameworkServlet.java:553)
at org.springframework.web.servlet.FrameworkServlet.initServletBean(FrameworkServlet.java:494)
at org.springframework.web.servlet.HttpServletBean.init(HttpServletBean.java:171)
at javax.servlet.GenericServlet.init(GenericServlet.java:158)
at org.apache.catalina.core.StandardWrapper.initServlet(StandardWrapper.java:1124)
at org.apache.catalina.core.StandardWrapper.loadServlet(StandardWrapper.java:1079)
at org.apache.catalina.core.StandardWrapper.load(StandardWrapper.java:971)
at org.apache.catalina.core.StandardContext.loadOnStartup(StandardContext.java:4829)
at org.apache.catalina.core.StandardContext.startInternal(StandardContext.java:5143)
at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:183)
at org.apache.catalina.core.StandardContext.reload(StandardContext.java:3716)
at org.apache.catalina.loader.WebappLoader.backgroundProcess(WebappLoader.java:292)
at org.apache.catalina.core.StandardContext.backgroundProcess(StandardContext.java:5465)
at org.apache.catalina.core.ContainerBase$ContainerBackgroundProcessor.processChildren(ContainerBase.java:1396)
at org.apache.catalina.core.ContainerBase$ContainerBackgroundProcessor.processChildren(ContainerBase.java:1400)
at org.apache.catalina.core.ContainerBase$ContainerBackgroundProcessor.processChildren(ContainerBase.java:1400)
at org.apache.catalina.core.ContainerBase$ContainerBackgroundProcessor.run(ContainerBase.java:1368)
at java.lang.Thread.run(Thread.java:748)
Caused by: org.springframework.beans.factory.NoSuchBeanDefinitionException: No qualifying bean of type 'domain.service.MainService' available: expected at least 1 bean which qualifies as autowire candidate. Dependency annotations: {@org.springframework.beans.factory.annotation.Autowired(required=true)}
at org.springframework.beans.factory.support.DefaultListableBeanFactory.raiseNoMatchingBeanFound(DefaultListableBeanFactory.java:1493)
at org.springframework.beans.factory.support.DefaultListableBeanFactory.doResolveDependency(DefaultListableBeanFactory.java:1104)
at org.springframework.beans.factory.support.DefaultListableBeanFactory.resolveDependency(DefaultListableBeanFactory.java:1066)
at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor$AutowiredFieldElement.inject(AutowiredAnnotationBeanPostProcessor.java:585)
... 33 more

我已经将我的实现类注释为@Service

@Service
public class MainServiceImpl implements someDAOClass{
@Autowired
private someDAOClass someDAOClass1;
@Transactional
public list<someDAOClass> getSomeDAOClass(){
//return statement here
}
}

此外，我的DAO类被注释为@Repository，非事务性。昨天，我只使用了一个DAO就达到了预期的结果，但现在我做了一些更改，我不确定为什么它不能一起工作。

我试过在我的控制器上使用@ComponentScan，以防万一，但那是徒劳的。当我使用STS(Eclipse(时，我似乎无法按照另一篇SO文章中的解决方案建议创建一个根包并将控制器保留在那里。因此，除了在系统资源管理器中更改体系结构之外，我正在寻找其他解决方案。

Answer 1

您的服务实现类应该实现service，而不是DAO

@Service
public class MainServiceImpl implements MainService {

您应该定义您的bean，例如：

@Bean
public MainService mainService(){
return new MainServiceImpl ();
}

Answer 2

错误显示，

没有"domain.service.MainService"类型的合格bean可用

MainServiceImpl是someDAOClass，而不是MainService。所以您应该实现MainService。