java - Spring 自动装配服务在我的控制器中不起作用

Question

为了在我的控制器中自动连接服务，我遇到了问题。我有这个错误：

org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'myController': Injection of autowired dependencies failed; nested exception is org.springframework.beans.factory.BeanCreationException: Could not autowire field: private es.unican.meteo.service.UserService es.unican.meteo.controller.MyController.userService; nested exception is org.springframework.beans.factory.NoSuchBeanDefinitionException: No matching bean of type [es.unican.meteo.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)}

似乎 userService 没有注册，所以控制器无法获取 bean。我认为我的配置没问题，因为它适用于测试。在测试中我有这个：

ClassPathXmlApplicationContext("/WEB-INF/app-config.xml");

我可以从 ApplicationContext.xml 获得 bean ok

我的包结构如下：

es.unican.meteo.controller

|---- MyController.java

es.unican.meteo.service

|---- 用户服务.java

es.unican.meteo.service.impl

|---- UserServiceImpl.java

......

网页内容/WEB-INF

|---- MyDispatcherServlet-servlet.xml

|---- 应用配置.xml

|---- web.xml

......

类：

== UserServiceImpl.java ==

@Service
public class UserServiceImpl implements UserService{

    @Autowired
    private UserMapper userMapper;

    public void setUserMapper(UserMapper userMapper) {
        this.userMapper = userMapper;
    }

== MyController.java ==

@Controller
public class MyController {

     @Autowired
     private UserService userService;

     @RequestMapping(method=RequestMethod.GET, value="/home")
     public String handleRequest(){
      return "welcome";
     }

     @RequestMapping(method=RequestMethod.GET, value="/getUsers")
     public @ResponseBody List<User> getUsersInJSON(){
      return userService.getUsers();
     }
}

== web.xml ==

<display-name>Spring MVC</display-name>

 <servlet>
  <servlet-name>MyDispatcherServlet</servlet-name>
  <servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
 </servlet>

 <servlet-mapping>
  <servlet-name>MyDispatcherServlet</servlet-name>
  <url-pattern>*.go</url-pattern>
 </servlet-mapping>
</web-app>

== app-config.xml ===

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xmlns:context="http://www.springframework.org/schema/context"
    xmlns:p="http://www.springframework.org/schema/p"
    xmlns:mvc="http://www.springframework.org/schema/mvc"
    xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-3.1.xsd
        http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-3.1.xsd
        http://www.springframework.org/schema/mvc http://www.springframework.org/schema/mvc/spring-mvc-3.1.xsd">


   <!-- Scans the classpath of this application for @Components to deploy as beans -->
   <context:component-scan base-package="es.unican.meteo" />

   <!-- Configures the @Controller programming model -->
   <mvc:annotation-driven/>

   <bean id="dataSource" class="org.springframework.jdbc.datasource.DriverManagerDataSource"
    p:driverClassName="org.apache.derby.jdbc.EmbeddedDriver"
    p:url="jdbc:derby:C:\tools\derbydb"
    p:connectionProperties=""
    p:username="APP"
    p:password="" />

    <bean id="transactionManager" class="org.springframework.jdbc.datasource.DataSourceTransactionManager">
        <property name="dataSource" ref="dataSource"/>
    </bean>

    <bean id="sqlSessionFactory" class="org.mybatis.spring.SqlSessionFactoryBean">
        <property name="dataSource" ref="dataSource" />
        <property name="configLocation" value="/mybatis-config.xml" />
    </bean> 

    <bean id="usersMapper" class="org.mybatis.spring.mapper.MapperFactoryBean">
        <property name="mapperInterface" value="es.unican.meteo.dao.UserMapper" />
        <property name="sqlSessionFactory" ref="sqlSessionFactory" />
    </bean> 

    <bean id="rolesMapper" class="org.mybatis.spring.mapper.MapperFactoryBean">
        <property name="mapperInterface" value="es.unican.meteo.dao.RoleMapper" />
        <property name="sqlSessionFactory" ref="sqlSessionFactory" />
    </bean> 

</beans>

== MyDispatcherServlet.xml ==

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
 xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
 xmlns:context="http://www.springframework.org/schema/context"
 xmlns:mvc="http://www.springframework.org/schema/mvc"
 xsi:schemaLocation="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-3.1.xsd
  http://www.springframework.org/schema/mvc http://www.springframework.org/schema/mvc/spring-mvc-3.1.xsd">

 <!-- Enabling Spring beans auto-discovery -->
 <context:component-scan base-package="es.unican.meteo.controller" />

 <!-- Enabling Spring MVC configuration through annotations -->
 <mvc:annotation-driven />

 <!-- Defining which view resolver to use -->
 <bean class= "org.springframework.web.servlet.view.InternalResourceViewResolver" > 
  <property name="prefix" value="/WEB-INF/views/" /> 
  <property name="suffix" value=".jsp" /> 
 </bean>

Spring mvc 记录器跟踪：

19:38:54,119 DEBUG http-8080-1 support.DefaultListableBeanFactory:430 - Creating instance of bean 'myController'
19:38:54,170 DEBUG http-8080-1 annotation.InjectionMetadata:60 - Found injected element on class [es.unican.meteo.controller.MyController]: AutowiredFieldElement for private es.unican.meteo.service.UserService es.unican.meteo.controller.MyController.userService
19:38:54,174 DEBUG http-8080-1 support.DefaultListableBeanFactory:504 - Eagerly caching bean 'myController' to allow for resolving potential circular references
19:38:54,206 DEBUG http-8080-1 annotation.InjectionMetadata:85 - Processing injected method of bean 'myController': AutowiredFieldElement for private es.unican.meteo.service.UserService es.unican.meteo.controller.MyController.userService
19:38:54,224 DEBUG http-8080-1 support.DefaultListableBeanFactory:217 - Creating shared instance of singleton bean 'userServiceImpl'
19:38:54,226 DEBUG http-8080-1 support.DefaultListableBeanFactory:430 - Creating instance of bean 'userServiceImpl'
19:38:54,234 DEBUG http-8080-1 annotation.InjectionMetadata:60 - Found injected element on class [es.unican.meteo.service.impl.UserServiceImpl]: AutowiredFieldElement for private es.unican.meteo.dao.UserMapper es.unican.meteo.service.impl.UserServiceImpl.userMapper
19:38:54,237 DEBUG http-8080-1 support.DefaultListableBeanFactory:504 - Eagerly caching bean 'userServiceImpl' to allow for resolving potential circular references
19:38:54,256 DEBUG http-8080-1 annotation.InjectionMetadata:85 - Processing injected method of bean 'userServiceImpl': AutowiredFieldElement for private es.unican.meteo.dao.UserMapper es.unican.meteo.service.impl.UserServiceImpl.userMapper
19:38:54,268  INFO http-8080-1 support.DefaultListableBeanFactory:433 - Destroying singletons in org.springframework.beans.factory.support.DefaultListableBeanFactory@56088b29: defining beans [myController,roleService,userServiceImpl,org.springframework.context.annotation.internalConfigurationAnnotationProcessor,org.springframework.context.annotation.internalAutowiredAnnotationProcessor,org.springframework.context.annotation.internalRequiredAnnotationProcessor,org.springframework.context.annotation.internalCommonAnnotationProcessor,org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerMapping#0,org.springframework.format.support.FormattingConversionServiceFactoryBean#0,org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter#0,org.springframework.web.servlet.handler.MappedInterceptor#0,org.springframework.web.servlet.mvc.method.annotation.ExceptionHandlerExceptionResolver#0,org.springframework.web.servlet.mvc.annotation.ResponseStatusExceptionResolver#0,org.springframework.web.servlet.mvc.support.DefaultHandlerExceptionResolver#0,org.springframework.web.servlet.handler.BeanNameUrlHandlerMapping,org.springframework.web.servlet.mvc.HttpRequestHandlerAdapter,org.springframework.web.servlet.mvc.SimpleControllerHandlerAdapter,org.springframework.web.servlet.view.InternalResourceViewResolver#0,org.springframework.context.annotation.ConfigurationClassPostProcessor$ImportAwareBeanPostProcessor#0]; root of factory hierarchy
19:38:54,279 ERROR http-8080-1 servlet.DispatcherServlet:457 - Context initialization failed

我已经查看了有关此主题的一些问题，但我没有找到解决问题的方法。也许我跳过了一些东西，但我不确定。我试图更改组件扫描但没有结果。

当我尝试访问 /SPRING-MVC/getUsers.go 时出现这些错误。

我不知道bean是否必须放在app-config（applicationContext）或servlet.xml中，因为它有点令人困惑......

谢谢

Answer 1

你的配置很奇怪...

首先排除明显的

我在您的web.xml. 会不会是你忘记添加这段代码了？

<context-param>
    <param-name>contextConfigLocation</param-name>
    <param-value>
        WEB-INF/app-config.xml
    </param-value>
</context-param>

<listener>
    <listener-class>org.springframework.web.context.ContextLoaderListener</listener-class>
</listener>

现在有点理论

一点 Spring 理论 - Spring 为 Web 应用程序使用应用程序上下文层次结构：

• 顶级 Web 应用程序上下文由ContextLoaderListener
• DispatcherServlet那么每个实例都有单独的上下文

当一个新的 bean 被实例化时，它可以从定义它的上下文或父上下文中获取依赖关系。这使得在根上下文（服务、DAO、...）中定义公共 bean 并在 servlet 应用程序上下文中具有请求处理 bean 成为可能，因为每个 servlet 都可以有自己的一组控制器、视图处理程序......

最后但并非最不重要的 - 你的错误

您正在根上下文中配置 MVC。那是错误的。从那里删除<mvc:上下文。

您还通过<context:component-scan>基础包在根上下文中注册控制器。仅对services包进行组件扫描，或者将您的类分成两个顶级包core（用于根 bean）和servlet（用于 servlet bean）。

Answer 2

确保您UserServiceImpl的包与context:component-scan. 如果不是，spring 将无法检测到它。另外，尝试从UserServiceImpl定义中删除 value 属性，因为该类型只有 1 个 bean。Spring 将能够按类型自动装配它。

Answer 3

您需要更改在控制器中自动连接服务的方式。

更改以下代码

@Autowired
private UserService userService;

有以下

@Resource(name="userService")
private UserService userService;

因为在 UserServiceImpl 中，您已经使用别名“userService”定义了 @Service 注释。

我希望这能解决你的问题。:)

Answer 4

当您遇到此类问题时，请检查，上下文的路径是什么：组件扫描基础包

它应该是根名称 就像我将 com.mike 作为包名并且在其结构中包含 bean、controller、dao、service 文件夹，那么在这种情况下，您必须遵循 Like ----context:component-scan basepackage ="com.mike.*"

其中 * 表示将扫描所有文件夹（bean、service、dao、controller 和对应的类）。

Answer 5

您可以@Qualifier按如下方式使用注释：

@Autowired
@Qualifier("userService")
private UserService userService;

Answer 6

乍一看，配置似乎没问题，但可能有一些较小的绊线可能不那么明显。

a) 实现的UserService接口，和控制器需要的一样吗？愚蠢的问题，我知道，但请注意安全。

b）bean name：尝试从注释中消除value-value（ba-da-tush） ，无论如何它都是多余的。@Service或者在@Qualifier.

c) 包扫描：仔细检查您实施的服务是否真的在es.unican.meteo. 有时是小事。

Answer 7

在您的服务上添加 @Component 注释。它应该可以正常工作