java.lang.IllegalArgumentException: Can't convert argument: null

org.apache.tomcat.util.digester.Digester endElement
SEVERE: End event threw exception
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)

上述问题是由于在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

可以把javaee字去掉，就ＯＫ了，

Xml代码

  <servlet>
    <servlet-name>dwr</servlet-name>
    <servlet-class>org.directwebremoting.servlet.DwrServlet</servlet-class>
    <init-param>
      <javaee:param-name>debug</javaee:param-name>
      <javaee:param-value>true</javaee:param-value>
    </init-param