spring MVC3错误无法实例化bean类[java.util.List]：指定的类是偶尔的接口

Question

I am using spring MVC3, I found code like below:

@Controller
class IndexController
{
    @ModelAttribute("allTags")
    public List<ArticleTag> allTags()
    {
        return Collections.emptyList();
    }
}

Sometimes errors with message

(Not always)

SEVERE: Servlet.service() for servlet [appServlet] in context with path [] threw exception [Request processing failed; nested exception is org.springframework.beans.BeanInstantiationException: Could not instantiate bean class [java.util.List]: Specified class is an interface] with root cause
org.springframework.beans.BeanInstantiationException: Could not instantiate bean class [java.util.List]: Specified class is an interface
        at org.springframework.beans.BeanUtils.instantiateClass(BeanUtils.java:101)
        at org.springframework.web.method.annotation.ModelAttributeMethodProcessor.createAttribute(ModelAttributeMethodProcessor.java:132)
        at org.springframework.web.servlet.mvc.method.annotation.ServletModelAttributeMethodProcessor.createAttribute(ServletModelAttributeMethodProcessor.java:81)
        at org.springframework.web.method.annotation.ModelAttributeMethodProcessor.resolveArgument(ModelAttributeMethodProcessor.java:103)
        at org.springframework.web.method.support.HandlerMethodArgumentResolverComposite.resolveArgument(HandlerMethodArgumentResolverComposite.java:75)
        at org.springframework.web.method.support.InvocableHandlerMethod.getMethodArgumentValues(InvocableHandlerMethod.java:156)
        at org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:117)
        at org.springframework.web.method.annotation.ModelFactory.invokeModelAttributeMethods(ModelFactory.java:123)
        at org.springframework.web.method.annotation.ModelFactory.initModel(ModelFactory.java:97)
        at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandlerMethod(RequestMappingHandlerAdapter.java:614)
        at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:578)
        at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:80)
        at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:923)
        at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:852)
        at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:882)
        at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:778)
        at javax.servlet.http.HttpServlet.service(HttpServlet.java:621)
        at javax.servlet.http.HttpServlet.service(HttpServlet.java:722)
        at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:305)

Someone Says, List is a interface, plz use ArrayList or LinkedList instead

But, My Question is, Why the code above is not always eror?

When the error above occured, not matter how to refresh the page, error continues, nevery disappear！But, If you restart tomcat, you have a good opportunity to walk through this error!If no error like above occur,it never occurs util next tomcat restart!

与类型为int或Integer的@ModelAttribute相同，很可能会出错，但在某些主机上，它永远不会发生

Answer 1

更改代码如下

public ArticleTag allTags()

有关更多信息，请参阅以下链接

[http://forum.spring.io/forum/spring-projects/data/nosql/724397-mapping-exception-with-mongodb-aggregation-framework][1]

另请参阅已修复的Mongo问题

[https://jira.spring.io/browse/DATAMONGO-229]