java - NoSuchBeanDefinitionException : No qualifying bean

Question

我在 Spring mvc 中遇到错误:

(org.springframework.beans.factory.BeanCreationException:创建名称为“webController”的bean时出错: Autowiring 依赖项注入(inject)失败；嵌套异常为org.springframework.beans.factory.BeanCreationException:无法 Autowiring 字段:private com. nickolay.app.service.UserService com.nickolay.app.WebController.userService；嵌套异常是 org.springframework.beans.factory.NoSuchBeanDefinitionException:找不到依赖项 [com.nickolay.app.service.UserService] 类型的合格 bean:预计至少有 1 个有资格作为此依赖项的 Autowiring 候选者的 bean。依赖项注释)

org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'webController': Injection of autowired dependencies failed; nested exception is org.springframework.beans.factory.BeanCreationException: Could not autowire field: private com.nickolay.app.service.UserService com.nickolay.app.WebController.userService; nested exception is org.springframework.beans.factory.NoSuchBeanDefinitionException: No qualifying bean of type [com.nickolay.app.service.UserService] 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:306)
    at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:230)
    at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:302)
    at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:197)
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.preInstantiateSingletons(DefaultListableBeanFactory.java:772)
    at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:839)
    at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:538)
    at org.springframework.web.servlet.FrameworkServlet.configureAndRefreshWebApplicationContext(FrameworkServlet.java:667)
    at org.springframework.web.servlet.FrameworkServlet.createWebApplicationContext(FrameworkServlet.java:633)
    at org.springframework.web.servlet.FrameworkServlet.createWebApplicationContext(FrameworkServlet.java:681)
    at org.springframework.web.servlet.FrameworkServlet.initWebApplicationContext(FrameworkServlet.java:552)
    at org.springframework.web.servlet.FrameworkServlet.initServletBean(FrameworkServlet.java:493)
    at org.springframework.web.servlet.HttpServletBean.init(HttpServletBean.java:136)
    at javax.servlet.GenericServlet.init(GenericServlet.java:158)
    at org.apache.catalina.core.StandardWrapper.initServlet(StandardWrapper.java:1231)
    at org.apache.catalina.core.StandardWrapper.loadServlet(StandardWrapper.java:1144)
    at org.apache.catalina.core.StandardWrapper.load(StandardWrapper.java:1031)
    at org.apache.catalina.core.StandardContext.loadOnStartup(StandardContext.java:4997)
    at org.apache.catalina.core.StandardContext.startInternal(StandardContext.java:5289)
    at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:150)
    at org.apache.catalina.core.StandardContext.reload(StandardContext.java:3831)
    at org.apache.catalina.loader.WebappLoader.backgroundProcess(WebappLoader.java:292)
    at org.apache.catalina.core.StandardContext.backgroundProcess(StandardContext.java:5616)
    at org.apache.catalina.core.ContainerBase$ContainerBackgroundProcessor.processChildren(ContainerBase.java:1377)
    at org.apache.catalina.core.ContainerBase$ContainerBackgroundProcessor.processChildren(ContainerBase.java:1381)
    at org.apache.catalina.core.ContainerBase$ContainerBackgroundProcessor.processChildren(ContainerBase.java:1381)
    at org.apache.catalina.core.ContainerBase$ContainerBackgroundProcessor.run(ContainerBase.java:1349)
    at java.lang.Thread.run(Thread.java:745)
Caused by: org.springframework.beans.factory.BeanCreationException: Could not autowire field: private com.nickolay.app.service.UserService com.nickolay.app.WebController.userService; nested exception is org.springframework.beans.factory.NoSuchBeanDefinitionException: No qualifying bean of type [com.nickolay.app.service.UserService] found for dependency: expected at least 1 bean which qualifies as autowire candidate for this dependency. Dependency annotations: {@org.springframework.beans.factory.annotation.Autowired(required=true)}
    at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor$AutowiredFieldElement.inject(AutowiredAnnotationBeanPostProcessor.java:573)
    at org.springframework.beans.factory.annotation.InjectionMetadata.inject(InjectionMetadata.java:88)
    at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor.postProcessPropertyValues(AutowiredAnnotationBeanPostProcessor.java:331)
    ... 31 more
Caused by: org.springframework.beans.factory.NoSuchBeanDefinitionException: No qualifying bean of type [com.nickolay.app.service.UserService] 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:1373)
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.doResolveDependency(DefaultListableBeanFactory.java:1119)
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.resolveDependency(DefaultListableBeanFactory.java:1014)
    at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor$AutowiredFieldElement.inject(AutowiredAnnotationBeanPostProcessor.java:545)
    ... 33 more

我的 Controller (WebController.java):

@Controller
public class WebController {


    @Autowired
    private UserService userService;

.................
}

我的UserService.java:

@Service
public class UserService implements UserServiceInterface {

    @Autowired
    private UserDao userDao;

    public void setUserDao(UserDao userDao) {
        this.userDao = userDao;
    }

    @Override
    @Transactional
    public void create(User user) {
        userDao.create(user);
    }
................
}

我的HibernateUserDao.java，它实现了UserDao:

@Repository("UserDao")
public class HibernateUserDao implements UserDao {

    @Autowired
    SessionFactory sessionFactory;

    public HibernateUserDao() {
    }

    @Override
    @Transactional
    public void create(User user) {
        if (user == null) {
            throw new NullPointerException();
        }
        Session session = sessionFactory.getCurrentSession();
        session.save(user);
    }
.............
}

我的servlet-contents.xml

<?xml version="1.0" encoding="UTF-8"?>
<beans:beans xmlns="http://www.springframework.org/schema/mvc"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:beans="http://www.springframework.org/schema/beans"
    xmlns:context="http://www.springframework.org/schema/context" xmlns:tx="http://www.springframework.org/schema/tx"
    xsi:schemaLocation="http://www.springframework.org/schema/mvc http://www.springframework.org/schema/mvc/spring-mvc.xsd
        http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd
        http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context.xsd
        http://www.springframework.org/schema/tx http://www.springframework.org/schema/tx/spring-tx-4.2.xsd"


    <annotation-driven />

    <tx:annotation-driven />

    <resources mapping="/resources/**" location="/resources/" />


    <beans:bean
        class="org.springframework.web.servlet.view.InternalResourceViewResolver">
        <beans:property name="prefix" value="/WEB-INF/views/" />
        <beans:property name="suffix" value=".jsp" />
    </beans:bean>

    <context:component-scan base-package="com.nickolay.app" />

    <beans:bean id="userDao" class="com.nickolay.app.dao.HibernateUserDao" />
    <beans:bean id="roleDao" class="com.nickolay.app.dao.HibernateRoleDao" />
    <beans:bean id="userService" class="com.nickolay.app.service.UserService">
    </beans:bean>


</beans:beans>

Answer 1

在这种情况下，您无法注入(inject)具体类 UserService。这是因为 Spring 正在为您的类创建一个代理，以便处理 @Transactional。由于您的服务实现了一个接口(interface)，Spring 正在创建一个基于 JDK 接口(interface)的代理，即代理实现 UserServiceInterface 并委托(delegate)给 UserService。因此Spring管理的bean不是UserService而是UserServiceInterface

有两种方法可以解决这个问题。最简单的方法是将依赖项从 UserService 更改为 UserServiceInterface

@Controller
public class WebController {

    @Autowired
    private UserServiceInterface userService;

}

第二种方法是指示 Spring 使用基于 CGLIB 类的代理而不是基于 JDK 接口(interface)的代理。更改您的 tx:annotation-driven 以将 proxy-target-class 指定为 true

<?xml version="1.0" encoding="UTF-8"?>
<beans:beans xmlns="http://www.springframework.org/schema/mvc"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:beans="http://www.springframework.org/schema/beans"
    xmlns:context="http://www.springframework.org/schema/context" xmlns:tx="http://www.springframework.org/schema/tx"
    xsi:schemaLocation="http://www.springframework.org/schema/mvc http://www.springframework.org/schema/mvc/spring-mvc.xsd
        http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd
        http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context.xsd
        http://www.springframework.org/schema/tx http://www.springframework.org/schema/tx/spring-tx-4.2.xsd"


    <annotation-driven />

    <tx:annotation-driven proxy-target-class="true/>

    <resources mapping="/resources/**" location="/resources/" />


    <beans:bean
        class="org.springframework.web.servlet.view.InternalResourceViewResolver">
        <beans:property name="prefix" value="/WEB-INF/views/" />
        <beans:property name="suffix" value=".jsp" />
    </beans:bean>

    <context:component-scan base-package="com.nickolay.app" />

    <beans:bean id="userDao" class="com.nickolay.app.dao.HibernateUserDao" />
    <beans:bean id="roleDao" class="com.nickolay.app.dao.HibernateRoleDao" />
    <beans:bean id="userService" class="com.nickolay.app.service.UserService">
    </beans:bean>


</beans:beans>