Question

我在Spring MVC 4中自动装配时遇到很大问题，我已经花了很多时间。找到了许多解决方案，但没有任何帮助。

我有控制器：

@Controller
public class PrintedBookController {
    @Autowired
    PrintedBookService pbookService; // interface

    @RequestMapping(value = "/pbook", method = RequestMethod.GET)
    public ModelAndView pbook() {
        return new ModelAndView("pbook", "command", new PrintedBookDTO());
    }
...
}

还有：

PrintedBookService // this is interface

PrintedBookServiceImpl // this is implementation of PrintedBookService

printbookserviceimpl中的

是：

@Service
@Transactional
public class PrintedBookServiceImpl implements PrintedBookService {

    @Autowired
    private PrintedBookDAO pbookDao;

    @Autowired
    private BookDAO bookDao;

    @Autowired
    private LoanDAO loanDao;


    public void setPrintedBookDao(PrintedBookDAO pbookDao) {
       this.pbookDao = pbookDao;
    }
    ....
}

PrintedBookServiceImpl中的daos是接口

dao实现如下所示：

public class PrintedBookDAOImpl implements PrintedBookDAO, GenericDAO<PrintedBook> {

    @PersistenceContext(unitName = "pbook-unit", type = PersistenceContextType.EXTENDED)
    private EntityManager em;
    ....
}

我有三个模块library-lib（daos）library-service（services）library-web（spring mvc）。库mvc有控制器xml：

<beans xmlns="http://www.springframework.org/schema/beans"
    xmlns:context="http://www.springframework.org/schema/context"
    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">

    <context:component-scan base-package="cz.fi.muni.pa165.library.web" />
    <context:component-scan base-package="cz.fi.muni.pa165.service" />
    <context:component-scan base-package="cz.fi.muni.pa165.dao" />


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

</beans>

和web.xml

<web-app id="WebApp_ID" version="2.4"
    xmlns="http://java.sun.com/xml/ns/j2ee" 
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee 
    http://java.sun.com/xml/ns/j2ee/web-app_2_4.xsd">

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

    <servlet>
        <servlet-name>mvc-dispatcher</servlet-name>
        <servlet-class>
                       org.springframework.web.servlet.DispatcherServlet
                </servlet-class>
        <load-on-startup>1</load-on-startup>
    </servlet>

    <servlet-mapping>
        <servlet-name>mvc-dispatcher</servlet-name>
        <url-pattern>/</url-pattern>
    </servlet-mapping>

    <context-param>
        <param-name>contextConfigLocation</param-name>
        <param-value>/WEB-INF/mvc-dispatcher-servlet.xml</param-value>
    </context-param>

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

</web-app>

当我运行web（在tomcat8上）时，它显示异常：

Caused by: org.springframework.beans.factory.BeanCreationException: Could not autowire field: cz.fi.muni.pa165.service.PrintedBookServiceImpl cz.fi.muni.pa165.library.web.PrintedBookController.pbookService; nested exception is org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'printedBookServiceImpl': Injection of autowired dependencies failed; nested exception is org.springframework.beans.factory.BeanCreationException: Could not autowire field: private cz.fi.muni.pa165.dao.PrintedBookDAO cz.fi.muni.pa165.service.PrintedBookServiceImpl.pbookDao; nested exception is org.springframework.beans.factory.NoSuchBeanDefinitionException: No qualifying bean of type [cz.fi.muni.pa165.dao.PrintedBookDAO] 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)}

和

Caused by: org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'printedBookServiceImpl': Injection of autowired dependencies failed; nested exception is org.springframework.beans.factory.BeanCreationException: Could not autowire field: private cz.fi.muni.pa165.dao.PrintedBookDAO cz.fi.muni.pa165.service.PrintedBookServiceImpl.pbookDao; nested exception is org.springframework.beans.factory.NoSuchBeanDefinitionException: No qualifying bean of type [cz.fi.muni.pa165.dao.PrintedBookDAO] 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)}

也得到了这个：

Caused by: org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'pbookDao': Injection of persistence dependencies failed; nested exception is org.springframework.beans.factory.NoSuchBeanDefinitionException: No bean named 'pbook-unit' is defined

该项目位于github https://github.com/Cospel/ProjLibrary 任何想法如何解决这个问题？

Answer 1

尝试在@Component上添加PrintedBookDAOImpl注释，Spring无法在上下文中找到任何类型PrintedBookDAO的bean。

查看跟踪的这一部分：

No qualifying bean of type [cz.fi.muni.pa165.dao.PrintedBookDAO] found for dependency: expected at least 1 bean which qualifies as autowire candidate for this dependency.

Answer 2

正如Jean所说，你需要将@Component添加到你想要自动装配的任何类中。对于服务，Spring通过使用@Service标记而不是@Component标记来提供一些优化。类似地，对于DAO层，Spring提供了优化的@Repository注释。使用这些注释可以为组件扫描启用这些类。那么，你甚至不需要

setPrintedBookDAO()

方法，因为Spring会照顾你的自动装配。

Spring MVC autowiring bean抛出nestedexception

2 个答案: