springMVC上传文件MultipartFile空属性问题

自己在使用springMVC时自己也是遇到了一个大坑，各项代码以及配置都是没什么问题，却遇到了如下问题：

HTTP Status 500 - Request processing failed; nested exception is java.lang.NullPointerException
type Exception report

message Request processing failed; nested exception is java.lang.NullPointerException

description The server encountered an internal error that prevented it from fulfilling this request.

exception

org.springframework.web.util.NestedServletException: Request processing failed; nested exception is java.lang.NullPointerException
	org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:986)
	org.springframework.web.servlet.FrameworkServlet.doPost(FrameworkServlet.java:881)
	javax.servlet.http.HttpServlet.service(HttpServlet.java:647)
	org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:855)
	javax.servlet.http.HttpServlet.service(HttpServlet.java:728)
	org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:200)
	org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)
root cause

java.lang.NullPointerException
	controller.UserController.fileuolaod2(UserController.java:79)
	sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
	sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	java.lang.reflect.Method.invoke(Method.java:498)
	org.springframework.web.method.support.InvocableHandlerMethod.doInvoke(InvocableHandlerMethod.java:209)
	org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:136)
	org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:102)
	org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandlerMethod(RequestMappingHandlerAdapter.java:871)
	org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:777)
	org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:87)
	org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:991)
	org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:925)
	org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:978)
	org.springframework.web.servlet.FrameworkServlet.doPost(FrameworkServlet.java:881)
	javax.servlet.http.HttpServlet.service(HttpServlet.java:647)
	org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:855)
	javax.servlet.http.HttpServlet.service(HttpServlet.java:728)
	org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:200)
	org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)
note The full stack trace of the root cause is available in the Apache Tomcat/7.0.39 logs.

我的文件配置及代码

springmvc.xml:

index.jsp:

springMVC文件上传

    选择文件：

    

Java类：

  @RequestMapping("/fileuolaod2")
    public String fileuolaod2(HttpServletRequest request, MultipartFile upload) throws Exception {

自己在测试的时候也是发现MultipartFile的值一直都是null，最后通过百度发现在“配置文件解析器对象”中的id值必须是固定的:

修改后的springmvc.xml:

最后这里也是记录一下，也希望能够帮到有需要的人。