一、Tomcat启动报错：
有时候我们会避免项目重名，在导入项目时会修改项目名称。
修改项目名称后启动该项目至tomcat，报错：java.lang.IllegalArgumentException: Can't convert argument: null
二、问题分析：
因为MyEclipse在修改项目名时候，自动更新部署了web.xml文件并且重新生成了xml文件的头部声明. 会将标签修改为 <javaee:param-name>这样的类型。
三、解决问题：
修改项目的web.xml，将其中带有javaee:的标签中的javaee:删掉即可，也可以直接Ctrl+F将javaee:直接全部替换为空。
四、报错信息如下：
java.lang.IllegalArgumentException: Can't convert argument: null
at org.apache.tomcat.util.IntrospectionUtils.convert(IntrospectionUtils.java:999)
at org.apache.tomcat.util.digester.CallMethodRule.end(CallMethodRule.java:523)
at org.apache.tomcat.util.digester.Rule.end(Rule.java:229)
at org.apache.tomcat.util.digester.Digester.endElement(Digester.java:1140)
at com.sun.org.apache.xerces.internal.parsers.AbstractSAXParser.endElement(Unknown Source)
at com.sun.org.apache.xerces.internal.impl.XMLDocumentFragmentScannerImpl.scanEndElement(Unknown Source)
at com.sun.org.apache.xerces.internal.impl.XMLDocumentFragmentScannerImpl$FragmentContentDispatcher.dispatch(Unknown Source)
at com.sun.org.apache.xerces.internal.impl.XMLDocumentFragmentScannerImpl.scanDocument(Unknown Source)
at com.sun.org.apache.xerces.internal.parsers.XML11Configuration.parse(Unknown Source)
at com.sun.org.apache.xerces.internal.parsers.XML11Configuration.parse(Unknown Source)
at com.sun.org.apache.xerces.internal.parsers.XMLParser.parse(Unknown Source)
at com.sun.org.apache.xerces.internal.parsers.AbstractSAXParser.parse(Unknown Source)
at org.apache.tomcat.util.digester.Digester.parse(Digester.java:1644)
at org.apache.catalina.startup.ContextConfig.applicationWebConfig(ContextConfig.java:365)
at org.apache.catalina.startup.ContextConfig.start(ContextConfig.java:1066)
at org.apache.catalina.startup.ContextConfig.lifecycleEvent(ContextConfig.java:261)
at org.apache.catalina.util.LifecycleSupport.fireLifecycleEvent(LifecycleSupport.java:117)
at org.apache.catalina.core.StandardContext.start(StandardContext.java:4252)
at org.apache.catalina.core.ContainerBase.addChildInternal(ContainerBase.java:791)
at org.apache.catalina.core.ContainerBase.addChild(ContainerBase.java:771)
at org.apache.catalina.core.StandardHost.addChild(StandardHost.java:525)
at org.apache.catalina.startup.HostConfig.deployDescriptor(HostConfig.java:627)
at org.apache.catalina.startup.HostConfig.deployDescriptors(HostConfig.java:553)
at org.apache.catalina.startup.HostConfig.deployApps(HostConfig.java:488)
at org.apache.catalina.startup.HostConfig.start(HostConfig.java:1149)
at org.apache.catalina.startup.HostConfig.lifecycleEvent(HostConfig.java:311)
at org.apache.catalina.util.LifecycleSupport.fireLifecycleEvent(LifecycleSupport.java:117)
at org.apache.catalina.core.ContainerBase.start(ContainerBase.java:1053)
at org.apache.catalina.core.StandardHost.start(StandardHost.java:719)
at org.apache.catalina.core.ContainerBase.start(ContainerBase.java:1045)
at org.apache.catalina.core.StandardEngine.start(StandardEngine.java:443)
at org.apache.catalina.core.StandardService.start(StandardService.java:516)
at org.apache.catalina.core.StandardServer.start(StandardServer.java:710)
at org.apache.catalina.startup.Catalina.start(Catalina.java:578)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
at java.lang.reflect.Method.invoke(Unknown Source)
at org.apache.catalina.startup.Bootstrap.start(Bootstrap.java:288)
at org.apache.catalina.startup.Bootstrap.main(Bootstrap.java:413)
问题是由于在Eclipse下重构JEE项目名时，Eclipse自动更新了部署文件web.xml,重新生成了xml文件的头部声明，新增加了javaee的命名空间：如下
<servlet>
  <javaee:display-name>MessageBrokerServlet</javaee:display-name>
  <servlet-name>MessageBrokerServlet</servlet-name>
  <servlet-class>flex.messaging.MessageBrokerServlet</servlet-class>
  <init-param>
    <javaee:param-name>services.configuration.file</javaee:param-name>
    <javaee:param-value>/WEB-INF/flex/services-config.xml</javaee:param-value>
  </init-param>
  <load-on-startup>1</load-on-startup>
</servlet>
将标签 <javaee:param-name> 中的javaee:删掉就完美解决问题，直接Ctrl+F将javaee:直接全部替换为空。 --------------------- 本文来自 Lemyou 的CSDN 博客 ，全文地址请点击：https://blog.csdn.net/Lemyou/article/details/80373024?utm_source=copy