org.apache.jasper.JasperException: Unable to compile class for JSP: (无法编译jsp)

郁闷啊。。今天在做一个小练习的时候，遇到

org.apache.jasper.JasperException: Unable to compile class for JSP: 

An error occurred at line: 9 in the jsp file: /dologin.jsp
username cannot be resolved
6: 	//鑾峰彇瀵嗙爜
7: 	String password=request.getParameter("password");
8: 	
9: 	System.out.println(username+":"+password);
10: %>
11: <html>
12:   <head>


Stacktrace:
	at org.apache.jasper.compiler.DefaultErrorHandler.javacError(DefaultErrorHandler.java:92)
	at org.apache.jasper.compiler.ErrorDispatcher.javacError(ErrorDispatcher.java:330)
	at org.apache.jasper.compiler.JDTCompiler.generateClass(JDTCompiler.java:423)
	at org.apache.jasper.compiler.Compiler.compile(Compiler.java:308)
	at org.apache.jasper.compiler.Compiler.compile(Compiler.java:286)
	at org.apache.jasper.compiler.Compiler.compile(Compiler.java:273)
	at org.apache.jasper.JspCompilationContext.compile(JspCompilationContext.java:566)
	at org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:317)
	at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:320)
	at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:266)
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:803)
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:290)
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
	at com.wabacusoa.util.SetCharacterEncodingFilter.doFilter(SetCharacterEncodingFilter.java:64)
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235)
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
	at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:230)
	at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:175)
	at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:128)
	at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:104)
	at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109)
	at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:261)
	at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:844)
	at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:581)
	at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:447)
	at java.lang.Thread.run(Thread.java:619)

这样的错误。遂慌张起来，于是乎，上网查资料，未能解决。QQ群里问高手，仍是没解决。后仔细斟酌：晕，仅仅一个字母之错。下面是我的dologin.jsp代码，很简单：

<%@ page language="java" import="java.util.*" contentType="text/html; charset=utf-8"%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<%
	//获取用户名
	String userName=request.getParameter("username");
	//获取密码
	String password=request.getParameter("password");
	
	System.out.println(username+":"+password);
%>
<html>
  <head>
    <title>登录处理页面</title>
  </head>
  
  <body>
  </body>
</html>

只因把userName写成了username。一个大写一个小写。就这，报了一个这错。。。现已解决。