SpringMVC下，前端MultipartFile上传文件始终是NULL，加上MutipartFile配置的bean，tomcat启动就报错。

一、问题描述

前端提交文件的html代码：

<form action="http://localhost:8080/untitled_war_exploded/upload/up" class="layui-form form form-horizontal" id="form-patient-add"
        enctype="multipart/form-data" method="post">
    <div class="layui-form-item">
      <input type="file" name="multipartFile" id="multipartFile"/>
    div>
    <button class="layui-btn" id="subbtn" type="submit">提交button>
  form>

后台接收文件代码：

类上面还有一个注解@RequestMapping("/upload")
@RequestMapping("/up")
    public void upload(@RequestParam(value = "multipartFile",required = false) MultipartFile multipartFile){
     
        System.out.println("1111");
        System.out.println("32232"+multipartFile);
        //获取原文件名
        String name = multipartFile.getOriginalFilename();
        //分割文件名，拿到文件类型
        String suffix = name.substring(name.lastIndexOf('.')+1,name.length());
        System.out.println(suffix);
        if(!suffix.equals("mp4")&&!suffix.equals("flv")&&!suffix.equals("avi")){
     
            System.out.println("对应文件格式不对");
        }
        String filename = new SimpleDateFormat("yyyyMMddHHmmss").format(new Date());

        File file = new File("D://");
        if(!file.exists()){
     
            file.mkdirs();
        }
        try {
     
            multipartFile.transferTo(new File(file+filename+"."+suffix));
        } catch (IOException e) {
     
            e.printStackTrace();
        }
    }

SpringMVC的xml配置

<bean id="multipartResolver" class="org.springframework.web.multipart.commons.CommonsMultipartResolver" >
        
        <property name="defaultEncoding" value="UTF-8"/>
        
        <property name="maxUploadSize" value="5242880000"/>
        
        <property name="maxInMemorySize" value="40960"/>
        

        
        <property name="resolveLazily" value="true"/>
    bean>

导入MutipartFile需要的依赖：

<dependency>
            <groupId>commons-iogroupId>
            <artifactId>commons-ioartifactId>
            <version>1.4version>
        dependency>

        
        <dependency>
            <groupId>commons-fileuploadgroupId>
            <artifactId>commons-fileuploadartifactId>
            <version>1.3.1version>
        dependency>

上面的配置都是正确的，按道理说可以启动tomcat了，但是它就是报错，如下：

25-Apr-2021 23:12:49.895 信息 [RMI TCP Connection(3)-127.0.0.1] org.apache.jasper.servlet.TldScanner.scanJars 至少有一个JAR被扫描用于TLD但尚未包含TLD。 为此记录器启用调试日志记录，以获取已扫描但未在其中找到TLD的完整JAR列表。 在扫描期间跳过不需要的JAR可以缩短启动时间和JSP编译时间。
25-Apr-2021 23:12:50.053 信息 [RMI TCP Connection(3)-127.0.0.1] org.springframework.web.servlet.FrameworkServlet.initServletBean Initializing Servlet 'SpringMVC'
25-Apr-2021 23:12:50.340 警告 [RMI TCP Connection(3)-127.0.0.1] org.springframework.context.support.AbstractApplicationContext.refresh Exception encountered during context initialization - cancelling refresh attempt: org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'multipartResolver': Lookup method resolution failed; nested exception is java.lang.IllegalStateException: Failed to introspect Class [org.springframework.web.multipart.commons.CommonsMultipartResolver] from ClassLoader [ParallelWebappClassLoader
  context: untitled_war_exploded
  delegate: false
----------> Parent Classloader:
java.net.URLClassLoader@4926097b
]
25-Apr-2021 23:12:50.343 严重 [RMI TCP Connection(3)-127.0.0.1] org.springframework.web.servlet.FrameworkServlet.initServletBean Context initialization failed
	org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'multipartResolver': Lookup method resolution failed; nested exception is java.lang.IllegalStateException: Failed to introspect Class [org.springframework.web.multipart.commons.CommonsMultipartResolver] from ClassLoader [ParallelWebappClassLoader
  context: untitled_war_exploded
  delegate: false
----------> Parent Classloader:
java.net.URLClassLoader@4926097b
]
		at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor.determineCandidateConstructors(AutowiredAnnotationBeanPostProcessor.java:289)
		at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.determineConstructorsFromBeanPostProcessors(AbstractAutowireCapableBeanFactory.java:1284)
		at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBeanInstance(AbstractAutowireCapableBeanFactory.java:1201)
		at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:564)
		at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:524)
		at org.springframework.beans.factory.support.AbstractBeanFactory.lambda$doGetBean$0(AbstractBeanFactory.java:335)
		at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:234)
		at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:333)
		at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:208)
		at org.springframework.beans.factory.support.DefaultListableBeanFactory.preInstantiateSingletons(DefaultListableBeanFactory.java:944)
		at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:918)
		at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:583)
		at org.springframework.web.servlet.FrameworkServlet.configureAndRefreshWebApplicationContext(FrameworkServlet.java:702)
		at org.springframework.web.servlet.FrameworkServlet.createWebApplicationContext(FrameworkServlet.java:668)
		at org.springframework.web.servlet.FrameworkServlet.createWebApplicationContext(FrameworkServlet.java:716)
		at org.springframework.web.servlet.FrameworkServlet.initWebApplicationContext(FrameworkServlet.java:591)
		at org.springframework.web.servlet.FrameworkServlet.initServletBean(FrameworkServlet.java:530)
		at org.springframework.web.servlet.HttpServletBean.init(HttpServletBean.java:170)
		at javax.servlet.GenericServlet.init(GenericServlet.java:158)
		at org.apache.catalina.core.StandardWrapper.initServlet(StandardWrapper.java:1134)
		at org.apache.catalina.core.StandardWrapper.loadServlet(StandardWrapper.java:1089)
		at org.apache.catalina.core.StandardWrapper.load(StandardWrapper.java:983)
		at org.apache.catalina.core.StandardContext.loadOnStartup(StandardContext.java:4902)
		at org.apache.catalina.core.StandardContext.startInternal(StandardContext.java:5206)
		at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:183)
		at org.apache.catalina.core.ContainerBase.addChildInternal(ContainerBase.java:717)
		at org.apache.catalina.core.ContainerBase.addChild(ContainerBase.java:690)
		at org.apache.catalina.core.StandardHost.addChild(StandardHost.java:706)
		at org.apache.catalina.startup.HostConfig.manageApp(HostConfig.java:1775)
		at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
		at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
		at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
		at java.lang.reflect.Method.invoke(Method.java:498)
		at org.apache.tomcat.util.modeler.BaseModelMBean.invoke(BaseModelMBean.java:288)
		at com.sun.jmx.interceptor.DefaultMBeanServerInterceptor.invoke(DefaultMBeanServerInterceptor.java:819)
		at com.sun.jmx.mbeanserver.JmxMBeanServer.invoke(JmxMBeanServer.java:801)
		at org.apache.catalina.mbeans.MBeanFactory.createStandardContext(MBeanFactory.java:460)
		at org.apache.catalina.mbeans.MBeanFactory.createStandardContext(MBeanFactory.java:408)
		at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
		at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
		at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
		at java.lang.reflect.Method.invoke(Method.java:498)
		at org.apache.tomcat.util.modeler.BaseModelMBean.invoke(BaseModelMBean.java:288)
		at com.sun.jmx.interceptor.DefaultMBeanServerInterceptor.invoke(DefaultMBeanServerInterceptor.java:819)
		at com.sun.jmx.mbeanserver.JmxMBeanServer.invoke(JmxMBeanServer.java:801)
		at com.sun.jmx.remote.security.MBeanServerAccessController.invoke(MBeanServerAccessController.java:468)
		at javax.management.remote.rmi.RMIConnectionImpl.doOperation(RMIConnectionImpl.java:1468)
		at javax.management.remote.rmi.RMIConnectionImpl.access$300(RMIConnectionImpl.java:76)
		at javax.management.remote.rmi.RMIConnectionImpl$PrivilegedOperation.run(RMIConnectionImpl.java:1309)
		at java.security.AccessController.doPrivileged(Native Method)
		at javax.management.remote.rmi.RMIConnectionImpl.doPrivilegedOperation(RMIConnectionImpl.java:1408)
		at javax.management.remote.rmi.RMIConnectionImpl.invoke(RMIConnectionImpl.java:829)
		at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
		at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
		at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
		at java.lang.reflect.Method.invoke(Method.java:498)
		at sun.rmi.server.UnicastServerRef.dispatch(UnicastServerRef.java:357)
		at sun.rmi.transport.Transport$1.run(Transport.java:200)
		at sun.rmi.transport.Transport$1.run(Transport.java:197)
		at java.security.AccessController.doPrivileged(Native Method)
		at sun.rmi.transport.Transport.serviceCall(Transport.java:196)
		at sun.rmi.transport.tcp.TCPTransport.handleMessages(TCPTransport.java:573)
		at sun.rmi.transport.tcp.TCPTransport$ConnectionHandler.run0(TCPTransport.java:834)
		at sun.rmi.transport.tcp.TCPTransport$ConnectionHandler.lambda$run$0(TCPTransport.java:688)
		at java.security.AccessController.doPrivileged(Native Method)
		at sun.rmi.transport.tcp.TCPTransport$ConnectionHandler.run(TCPTransport.java:687)
		at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
		at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
		at java.lang.Thread.run(Thread.java:748)
	Caused by: java.lang.IllegalStateException: Failed to introspect Class [org.springframework.web.multipart.commons.CommonsMultipartResolver] from ClassLoader [ParallelWebappClassLoader
  context: untitled_war_exploded
  delegate: false
----------> Parent Classloader:
java.net.URLClassLoader@4926097b
]
		at org.springframework.util.ReflectionUtils.getDeclaredMethods(ReflectionUtils.java:481)
		at org.springframework.util.ReflectionUtils.doWithLocalMethods(ReflectionUtils.java:321)
		at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor.determineCandidateConstructors(AutowiredAnnotationBeanPostProcessor.java:267)
		... 68 more
	Caused by: java.lang.NoClassDefFoundError: org/apache/commons/fileupload/FileItemFactory
		at java.lang.Class.getDeclaredMethods0(Native Method)
		at java.lang.Class.privateGetDeclaredMethods(Class.java:2701)
		at java.lang.Class.getDeclaredMethods(Class.java:1975)
		at org.springframework.util.ReflectionUtils.getDeclaredMethods(ReflectionUtils.java:463)
		... 70 more
	Caused by: java.lang.ClassNotFoundException: org.apache.commons.fileupload.FileItemFactory
		at org.apache.catalina.loader.WebappClassLoaderBase.loadClass(WebappClassLoaderBase.java:1364)
		at org.apache.catalina.loader.WebappClassLoaderBase.loadClass(WebappClassLoaderBase.java:1187)
		... 74 more

这个真的把我搞死了，搞了一整天了，把网上的博客看完了，都没能解决这个问题。忘了一个最容易忽略的细节。

二、解决问题

大家以后一定要注意，遇到web项目一定要去查看lib目录，查看依赖是否都导入了tomcat！！！！！


最后将所有的依赖加入lib目录

最后保存，重启项目，即可解决SpringMVC下，增加MutipartFile的bean后，启动tomcat报错的问题。如遇其他问题欢迎大家留言。