@Autowired注释与弹簧无法正常工作

Question

我对我的Maven项目，具有用户类的域图层，具有CRUD功能的服务的数据图层以及具有控制器类的Web图层具有Restful设计。但是，当我运行该项目，我得到以下错误：

javax.servlet.ServletException: Servlet.init() for servlet appServlet threw exception 
org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:472) 
........ 
java.lang.Thread.run(Thread.java:680) 


root cause 

    org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'userController': Injection of autowired dependencies failed; nested    
    exception is org.springframework.beans.factory.BeanCreationException: Could not autowire field: ........service.UserService org. 
    bk.samples.mvc.UserController.userService; nested exception is org.springframework.beans.factory.NoSuchBeanDefinitionException: No matching bean of type [se. 
    datalayer.guards.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)} 
    org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:225) .......... 

root cause 

org.springframework.beans.factory.BeanCreationException: Could not autowire field: .........service.UserService 
org.bk.samples.mvc.UserController.userService; nested exception is org.springframework.beans.factory.NoSuchBeanDefinitionException: No matching bean of type 
[se.datalayer.guards.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)} .......... 

root cause 

org.springframework.beans.factory.NoSuchBeanDefinitionException: No matching bean of type [.........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)} 
    org.springframework.beans.factory.support.DefaultListableBeanFactory.raiseNoSuchBeanDefinitionException(DefaultListableBeanFactory.java:924) 
    org.springframework.beans.factory.support.DefaultListableBeanFactory.doResolveDependency(DefaultListableBeanFactory.java:793) ....... 

然后我删除了@Autowired注释，但得到的错误如下：

org.springframework.web.util.NestedServletException: Request processing failed; nested exception is java.lang.NullPointerException 
     org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:894) 
     org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:778) 
     javax.servlet.http.HttpServlet.service(HttpServlet.java:621) 
     javax.servlet.http.HttpServlet.service(HttpServlet.java:722) 

    root cause 

    java.lang.NullPointerException 
     org.bk.samples.mvc.UserController.allUsers(UserController.java:32) 
     sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method).......... 

我userController类是：

@Controller 
@RequestMapping(value="/") 
public class UserController 
{ 
    @Autowired 
    UserService userService; 

    @RequestMapping(value="/users", method=RequestMethod.GET) 
    public ModelAndView allUsers() 
    { 

    ModelAndView mvd= new ModelAndView(); 
    Collection<User> allUsers= new ArrayList<User>(); 
    allUsers= userService.findAllUsers(); 
    System.out.println(allUsers); 
    mvd.addObject("allUsers", allUsers); 
    return mvd; 
    } 
}   

我不知道是什么导致了这个问题，我会很感激任何帮助。

Answer 1

它与Maven无关。你的Spring配置有问题。它告诉你，你没有定义UserService类型的Spring bean，所以它不能创建你的控制器bean，因为它依赖于拥有一个UserService（通过@Autowired注解表达）。您可能想看看overview of the Spring container和/或Spring MVC framework。

Answer 2

这很可能是您的web应用程序弹簧配置错误，并且与maven无关。无论你在哪里引导春天，你都可能包括你的webapp配置，但不包括你的数据层spring bean。