莫名其妙的一个问题!!

http://127.0.0.1:8080/struts-examples/welcome.do
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exception javax.servlet.ServletException: javax/servlet/jsp/tagext/TagExtraInfo
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:244)
javax.servlet.http.HttpServlet.service(HttpServlet.java:802)
org.apache.struts.action.RequestProcessor.doForward(RequestProcessor.java:1062)
org.apache.struts.action.RequestProcessor.internalModuleRelativeForward(RequestProcessor.java:1000)
org.apache.struts.action.RequestProcessor.processForward(RequestProcessor.java:560)
org.apache.struts.action.RequestProcessor.process(RequestProcessor.java:209)
org.apache.struts.action.ActionServlet.process(ActionServlet.java:1196)
org.apache.struts.action.ActionServlet.doGet(ActionServlet.java:414)
javax.servlet.http.HttpServlet.service(HttpServlet.java:689)
javax.servlet.http.HttpServlet.service(HttpServlet.java:802)
root cause java.lang.NoClassDefFoundError: javax/servlet/jsp/tagext/TagExtraInfo
java.lang.ClassLoader.defineClass0(Native Method)
java.lang.ClassLoader.defineClass(ClassLoader.java:539)
java.security.SecureClassLoader.defineClass(SecureClassLoader.java:123)
java.net.URLClassLoader.defineClass(URLClassLoader.java:251)
java.net.URLClassLoader.access$100(URLClassLoader.java:55)
java.net.URLClassLoader$1.run(URLClassLoader.java:194)
java.security.AccessController.doPrivileged(Native Method)
java.net.URLClassLoader.findClass(URLClassLoader.java:187)
java.lang.ClassLoader.loadClass(ClassLoader.java:289)
java.lang.ClassLoader.loadClass(ClassLoader.java:282)
sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:274)
java.lang.ClassLoader.loadClass(ClassLoader.java:235)
org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1255)
org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1189)
org.apache.jasper.compiler.TagLibraryInfoImpl.createTagInfo(TagLibraryInfoImpl.java:419)
org.apache.jasper.compiler.TagLibraryInfoImpl.parseTLD(TagLibraryInfoImpl.java:248)
org.apache.jasper.compiler.TagLibraryInfoImpl.<init>(TagLibraryInfoImpl.java:162)
org.apache.jasper.compiler.Parser.parseTaglibDirective(Parser.java:418)
org.apache.jasper.compiler.Parser.parseDirective(Parser.java:483)
org.apache.jasper.compiler.Parser.parseElements(Parser.java:1539)
org.apache.jasper.compiler.Parser.parse(Parser.java:126)
org.apache.jasper.compiler.ParserController.doParse(ParserController.java:220)
org.apache.jasper.compiler.ParserController.parse(ParserController.java:101)
org.apache.jasper.compiler.Compiler.generateJava(Compiler.java:203)
org.apache.jasper.compiler.Compiler.compile(Compiler.java:470)
org.apache.jasper.compiler.Compiler.compile(Compiler.java:451)
org.apache.jasper.compiler.Compiler.compile(Compiler.java:439)
org.apache.jasper.JspCompilationContext.compile(JspCompilationContext.java:511)
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:295)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:292)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:236)
javax.servlet.http.HttpServlet.service(HttpServlet.java:802)
org.apache.struts.action.RequestProcessor.doForward(RequestProcessor.java:1062)
org.apache.struts.action.RequestProcessor.internalModuleRelativeForward(RequestProcessor.java:1000)
org.apache.struts.action.RequestProcessor.processForward(RequestProcessor.java:560)
org.apache.struts.action.RequestProcessor.process(RequestProcessor.java:209)
org.apache.struts.action.ActionServlet.process(ActionServlet.java:1196)
org.apache.struts.action.ActionServlet.doGet(ActionServlet.java:414)
javax.servlet.http.HttpServlet.service(HttpServlet.java:689)
javax.servlet.http.HttpServlet.service(HttpServlet.java:802)
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这个是csdn里的同一个问题 http://community.csdn.net/Expert/topic/4211/4211049.xml?temp=.8019983
但是我昨天还能正常运行的啊！今天怎么就不行了？！！ 环境变量什么的 我都没动过啊！难道真的要象这位兄弟一样搞到系统重装？！