Question

我的Maven项目有Restful设计，带有用户类的域层，带有CRUD功能的服务的数据层和带有控制器类的Web层。但是当我运行项目时，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，但得到了以下错误：

    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)..........

我的userController课程是：

@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，我将不胜感激。

Answer 1

它与Maven无关。您的Spring配置有问题。它告诉你没有定义UserService类型的Spring bean，所以它不能创建你的控制器bean，因为它依赖于具有UserService（通过@Autowired注释表示）。您可能需要查看overview of the Spring container和/或Spring MVC framework。

Answer 2

您的网络应用中可能存在弹簧配置错误，与maven无关。无论你在哪里引导spring，你都可能包括你的webapp配置，但不包括你的数据层spring bean。

@Autowired注释与spring无法正常工作

2 个答案: