xml Java Web Servlet更新

Question

我有一个应用程序正在使用2.3servlet，我需要更新它，以使用3.0servlet。 更新<web-app>标记以匹配新Servlet时，会出现以下错误：

org.apache.catalina.LifecycleException: Failed to start component [StandardServer[8005]] Caused by: org.apache.catalina.LifecycleException: Failed to start component [StandardService[Catalina]] Caused by: org.apache.catalina.LifecycleException: Failed to start component [StandardEngine[Catalina].StandardHost[localhost]] Caused by: org.apache.tomcat.util.bcel.classfile.ClassFormatException: null is not a Java .class file

我的网络。xml头看起来像：

<?xml version="1.0" encoding="UTF-8"?>

<web-app version="3.0" xmlns="http://java.sun.com/xml/ns/javaee" 
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 
xsi:schemaLocation="http://java.sun.com/xml/ns/javaee                       
http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd">"

谁能告诉我我错过了什么