严重: 在路径为/DemoStruts2的上下文中，Servlet[jsp]的Servlet.service（）引发了具有根本原因的异常/login.jsp (行.: [12], 列: [0]) 无法为TAG [s:a]加载标记处理程序类[org.apache.struts2.views.jsp.ui.AnchorTag]
org.apache.jasper.JasperException: /login.jsp (行.: [12], 列: [0]) 无法为TAG [s:a]加载标记处理程序类[org.apache.struts2.views.jsp.ui.AnchorTag]
at org.apache.jasper.compiler.DefaultErrorHandler.jspError(DefaultErrorHandler.java:42)
at org.apache.jasper.compiler.ErrorDispatcher.dispatch(ErrorDispatcher.java:292)
at org.apache.jasper.compiler.ErrorDispatcher.jspError(ErrorDispatcher.java:98)
at org.apache.jasper.compiler.Parser.parseCustomTag(Parser.java:1241)
at org.apache.jasper.compiler.Parser.parseElements(Parser.java:1470)
at org.apache.jasper.compiler.Parser.parse(Parser.java:144)
at org.apache.jasper.compiler.ParserController.doParse(ParserController.java:244)
at org.apache.jasper.compiler.ParserController.parse(ParserController.java:105)
at org.apache.jasper.compiler.Compiler.generateJava(Compiler.java:206)
at org.apache.jasper.compiler.Compiler.compile(Compiler.java:386)
at org.apache.jasper.compiler.Compiler.compile(Compiler.java:362)
at org.apache.jasper.compiler.Compiler.compile(Compiler.java:346)
at org.apache.jasper.JspCompilationContext.compile(JspCompilationContext.java:605)
at org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:400)
at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:385)
at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:329)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:733)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:231)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:53)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:202)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:97)
at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:542)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:143)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:92)
at org.apache.catalina.valves.AbstractAccessLogValve.invoke(AbstractAccessLogValve.java:690)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:78)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:343)
at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:374)
at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:65)
at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:868)
at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1590)
at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
at java.lang.Thread.run(Thread.java:745)
报错部分的代码：
<%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8"%>
<%@ taglib prefix="s" uri="/struts-tags" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>用户登录</title>
</head>
<body>
<div align="left">
<s:a href="register.jsp">
<font color="blue">
<h5>还未注册？点击注册</h5>
</font>
</s:a>
</div>
<div>
<s:form action="login" method="post">
<s:textfield name="username" label="账号"></s:textfield>
<s:password name="password" label="密码"></s:password>
<s:submit value="登录"></s:submit>
</s:form>
</div>
</body>
</html>
