Question

一个奇怪的问题正在发生，当我使用<context:component-scan>然后我的映射工作正常但是Could not autowire field:，引发了自动接线的问题，但如果我删除了 <context:component-scan>然后所有自动布线工作正常但所有映射都不起作用。

我不明白什么是错的。

MVC-调度-servlet.xml中

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
    xmlns:context="http://www.springframework.org/schema/context"
    xmlns:mvc="http://www.springframework.org/schema/mvc" 
        xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="
        http://www.springframework.org/schema/beans     
        http://www.springframework.org/schema/beans/spring-beans-3.0.xsd
        http://www.springframework.org/schema/context 
        http://www.springframework.org/schema/context/spring-context-3.0.xsd
        http://www.springframework.org/schema/mvc
        http://www.springframework.org/schema/mvc/spring-mvc-3.0.xsd">

    <context:component-scan base-package="org.delance" />  
    <mvc:annotation-driven />           

    <bean id="multipartResolver"
           class="org.springframework.web.multipart.commons.CommonsMultipartResolver"/>

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

    <bean class="org.springframework.web.servlet.mvc.annotation.AnnotationMethodHandlerAdapter">
        <property name="cacheSeconds" value="0" />
    </bean>

    <bean
        class="org.springframework.web.servlet.view.InternalResourceViewResolver">
        <property name="prefix">
            <value>/</value>
        </property>
        <property name="suffix">
            <value>.jsp</value>
        </property>
    </bean>

</beans>

spring.xml

    <!-- DAO Implementations -->
<bean id="usersImp" class="org.delance.daoimplementation.UsersImp" />
<bean id="jobsDAOImp" class="org.delance.daoimplementation.JobsDAOImp" />

<!-- DAO -->
<bean id="jobsDAO" class="org.delance.dao.JobsDAO" />
<bean id="jobsService" class="org.delance.service.JobsService" />

<!-- Service Implementations -->
<bean id="jobsServiceImp" class="org.delance.serviceimp.JobsServiceImp" />

JobsDAO

public interface JobsDAO {
        public boolean addJobs(JobsBean jobs);
        public boolean deleteJobs();
        public List<JobsBean> findJobs(String query); 
}

JobsServiceImp.java

@Service
@Transactional(readOnly=true)
public class JobsServiceImp implements JobsService {

    @Autowired 
    @Qualifier("jobsDAOImp")
    private JobsDAO jobsDAO;

JobsController.java

@Controller
@RequestMapping(value="/")
public class JobsController {

        @Autowired
        @Qualifier("jobsServiceImp")
        private JobsService jobsService;

        @RequestMapping(value="/AddJobs", method = RequestMethod.POST)
        public String addJobs(JobsBean jobsBean, ModelMap model) {              
                if(jobsService.addJobs(jobsBean)) {
                     return "SuccessJobs";
                } else {
                     return "ErrorJobs";
                }
        }
    @RequestMapping(value="/Create", method = RequestMethod.GET)
    public String creatJobView(ModelMap model) {
            return "createJobs";
    }

    public JobsService getJobsService() {
        return jobsService;
    }

    public void setJobsService(JobsService jobsService) {
        this.jobsService = jobsService;
    }
}

堆栈跟踪

   SEVERE: Context initialization failed
org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'jobsController': Injection of autowired dependencies failed; nested exception is org.springframework.beans.factory.BeanCreationException: Could not autowire field: private org.delance.service.JobsService org.delance.controllers.JobsController.jobsService; nested exception is org.springframework.beans.factory.NoSuchBeanDefinitionException: No qualifying bean of type [org.delance.service.JobsService] 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), @org.springframework.beans.factory.annotation.Qualifier(value=jobsServiceImp)}
    at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor.postProcessPropertyValues(AutowiredAnnotationBeanPostProcessor.java:289)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.populateBean(AbstractAutowireCapableBeanFactory.java:1146)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:519)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:458)
    at org.springframework.beans.factory.support.AbstractBeanFactory$1.getObject(AbstractBeanFactory.java:296)
    at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:223)
    at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:293)
    at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:194)
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.preInstantiateSingletons(DefaultListableBeanFactory.java:628)
    at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:932)
    at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:479)
    at org.springframework.web.context.ContextLoader.configureAndRefreshWebApplicationContext(ContextLoader.java:410)
    at org.springframework.web.context.ContextLoader.initWebApplicationContext(ContextLoader.java:306)
    at org.springframework.web.context.ContextLoaderListener.contextInitialized(ContextLoaderListener.java:112)
    at org.apache.catalina.core.StandardContext.listenerStart(StandardContext.java:4939)
    at org.apache.catalina.core.StandardContext.startInternal(StandardContext.java:5434)
    at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:150)
    at org.apache.catalina.core.ContainerBase.addChildInternal(ContainerBase.java:901)
    at org.apache.catalina.core.ContainerBase.addChild(ContainerBase.java:877)
    at org.apache.catalina.core.StandardHost.addChild(StandardHost.java:633)
    at org.apache.catalina.startup.HostConfig.deployDescriptor(HostConfig.java:656)
    at org.apache.catalina.startup.HostConfig$DeployDescriptor.run(HostConfig.java:1635)
    at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:471)
    at java.util.concurrent.FutureTask.run(FutureTask.java:262)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)
    at java.lang.Thread.run(Thread.java:744)
Caused by: org.springframework.beans.factory.BeanCreationException: Could not autowire field: private org.delance.service.JobsService org.delance.controllers.JobsController.jobsService; nested exception is org.springframework.beans.factory.NoSuchBeanDefinitionException: No qualifying bean of type [org.delance.service.JobsService] 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), @org.springframework.beans.factory.annotation.Qualifier(value=jobsServiceImp)}
    at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor$AutowiredFieldElement.inject(AutowiredAnnotationBeanPostProcessor.java:517)
    at org.springframework.beans.factory.annotation.InjectionMetadata.inject(InjectionMetadata.java:87)
    at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor.postProcessPropertyValues(AutowiredAnnotationBeanPostProcessor.java:286)
    ... 26 more
Caused by: org.springframework.beans.factory.NoSuchBeanDefinitionException: No qualifying bean of type [org.delance.service.JobsService] found for dependency: expected at least 1 bean which qualifies as autowire candidate for this dependency. Dependency annotations: {@org.springframework.beans.factory.annotation.Autowired(required=true), @org.springframework.beans.factory.annotation.Qualifier(value=jobsServiceImp)}
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.raiseNoSuchBeanDefinitionException(DefaultListableBeanFactory.java:988)
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.doResolveDependency(DefaultListableBeanFactory.java:858)
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.resolveDependency(DefaultListableBeanFactory.java:770)
    at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor$AutowiredFieldElement.inject(AutowiredAnnotationBeanPostProcessor.java:489)
    ... 28 more

Feb 19, 2014 12:10:12 PM org.apache.catalina.core.StandardContext listenerStart
SEVERE: Exception sending context initialized event to listener instance of class org.springframework.web.context.ContextLoaderListener
org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'jobsController': Injection of autowired dependencies failed; nested exception is org.springframework.beans.factory.BeanCreationException: Could not autowire field: private org.delance.service.JobsService org.delance.controllers.JobsController.jobsService; nested exception is org.springframework.beans.factory.NoSuchBeanDefinitionException: No qualifying bean of type [org.delance.service.JobsService] 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), @org.springframework.beans.factory.annotation.Qualifier(value=jobsServiceImp)}
    at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor.postProcessPropertyValues(AutowiredAnnotationBeanPostProcessor.java:289)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.populateBean(AbstractAutowireCapableBeanFactory.java:1146)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:519)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:458)
    at org.springframework.beans.factory.support.AbstractBeanFactory$1.getObject(AbstractBeanFactory.java:296)
    at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:223)
    at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:293)
    at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:194)
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.preInstantiateSingletons(DefaultListableBeanFactory.java:628)
    at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:932)
    at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:479)
    at org.springframework.web.context.ContextLoader.configureAndRefreshWebApplicationContext(ContextLoader.java:410)
    at org.springframework.web.context.ContextLoader.initWebApplicationContext(ContextLoader.java:306)
    at org.springframework.web.context.ContextLoaderListener.contextInitialized(ContextLoaderListener.java:112)
    at org.apache.catalina.core.StandardContext.listenerStart(StandardContext.java:4939)
    at org.apache.catalina.core.StandardContext.startInternal(StandardContext.java:5434)
    at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:150)
    at org.apache.catalina.core.ContainerBase.addChildInternal(ContainerBase.java:901)
    at org.apache.catalina.core.ContainerBase.addChild(ContainerBase.java:877)
    at org.apache.catalina.core.StandardHost.addChild(StandardHost.java:633)
    at org.apache.catalina.startup.HostConfig.deployDescriptor(HostConfig.java:656)
    at org.apache.catalina.startup.HostConfig$DeployDescriptor.run(HostConfig.java:1635)
    at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:471)
    at java.util.concurrent.FutureTask.run(FutureTask.java:262)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)
    at java.lang.Thread.run(Thread.java:744)
Caused by: org.springframework.beans.factory.BeanCreationException: Could not autowire field: private org.delance.service.JobsService org.delance.controllers.JobsController.jobsService; nested exception is org.springframework.beans.factory.NoSuchBeanDefinitionException: No qualifying bean of type [org.delance.service.JobsService] 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), @org.springframework.beans.factory.annotation.Qualifier(value=jobsServiceImp)}
    at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor$AutowiredFieldElement.inject(AutowiredAnnotationBeanPostProcessor.java:517)
    at org.springframework.beans.factory.annotation.InjectionMetadata.inject(InjectionMetadata.java:87)
    at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor.postProcessPropertyValues(AutowiredAnnotationBeanPostProcessor.java:286)
    ... 26 more
Caused by: org.springframework.beans.factory.NoSuchBeanDefinitionException: No qualifying bean of type [org.delance.service.JobsService] found for dependency: expected at least 1 bean which qualifies as autowire candidate for this dependency. Dependency annotations: {@org.springframework.beans.factory.annotation.Autowired(required=true), @org.springframework.beans.factory.annotation.Qualifier(value=jobsServiceImp)}
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.raiseNoSuchBeanDefinitionException(DefaultListableBeanFactory.java:988)
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.doResolveDependency(DefaultListableBeanFactory.java:858)
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.resolveDependency(DefaultListableBeanFactory.java:770)
    at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor$AutowiredFieldElement.inject(AutowiredAnnotationBeanPostProcessor.java:489)
    ... 28 more

Answer 1

你需要了解每个

<context:component-scan base-package="org.delance" />  
<mvc:annotation-driven />

做。

component-scan扫描指定的包并注册它找到的任何bean定义，即。用@Component注释的类及其特化（如@Controller）。

annotation-driven查看ApplicationContext中的所有bean。如果它们是@Controller bean并且具有@RequestMapping方法，则会使用DispatcherServlet为它们注册特殊处理程序。

换句话说，你需要这两者。 component-scan生成bean，annotation-driven将它们注册到MVC堆栈中。

如果您遇到自动装配问题，则ApplicationContext设置不正确。

Answer 2

<context:component scan>扫描您的配置文件以获取特定注释（@ Component，@ Controller，@ Service和@Repository），如果它看到它们，则在您的上下文中创建它们的实例。

<mvc:annotation-driven>将扫描所有其他标记并执行与该注释关联的任何内容。因此，对于@RequestMapping，它会看到并将其注册为该url模式的处理程序。

您的配置需要两者。您看到“无法自动装配”错误的原因是因为您的注释驱动上下文会看到@Autowired注释，但没有正确类型的候选者来连接它。

因为你有

@Qualifier("jobsServiceImp")
private JobsService jobsService;

您需要创建一个ID为“jobsServiceImp”的JobService bean，以便它可以自动装配

<bean id="jobsServiceImp" class="my.package.JobService"/>

或者，如果使用@Component（“jobsServiceImp”）注释注释JobService类，则组件扫描将拾取它并使用给定的限定符自动创建bean。

如果您仍然收到autowire failed错误，请查看堆栈跟踪。有可能它无法创建JobServiceImp的实例，因为它本身具有@Autowired依赖项，没有候选者。

编辑：发布错误后，很明显。

找不到[org.delance.dao.JobsDAO]类型的限定bean 依赖：预计至少有1个bean有资格成为autowire 这种依赖的候选人。依赖注释： {@ org.springframework.beans.factory.annotation.Autowired（所需=真）， @ org.springframework.beans.factory.annotation.Qualifier（值= jobsDAOImp）} 在org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor $ AutowiredFieldElement.inject（AutowiredAnnotationBeanPostProcessor.java:517）

它说它无法创建你的JobsServiceImp，因为它需要一个JobsDAO。

创建一个JobsDAO bean来填充这个依赖关系，你应该好好去

<bean id="jobsDAOImp" class="org.delance.dao.JobsDao"/>

请注意，如果@Autowired为JobsDAO附加@Qualifier（'name'），您需要确保bean名称与@Autowired匹配。我想我看到了你的堆栈跟踪'jobsDAOImp'。

Answer 3

因为你有

<context:component-scan base-package="org.delance" />

您不需要在xml文件中外部创建bean。

将@Service，@ Controller，@ Repository，@ Component注释保留在您要创建bean的类的顶部就足够了。 Spring容器会自动为您创建bean。既然你已经保留了那些注释

删除spring.xml中的定义
删除控制器和服务中的@Qualifier注释

尝试立即运行该应用程序

使用组件扫描和自动装配在Spring中请求映射

3 个答案: