数组的下标越界问题

type Exception reportmessage description The server encountered an internal error () that prevented it from fulfilling this request.exception java.lang.IndexOutOfBoundsException: Index: 0, Size: 0
java.util.ArrayList.RangeCheck(Unknown Source)
java.util.ArrayList.get(Unknown Source)
service.XMima.Mima(XMima.java:13)
Servlet.Smima.doGet(Smima.java:21)
Servlet.Smima.doPost(Smima.java:31)
javax.servlet.http.HttpServlet.service(HttpServlet.java:710)
javax.servlet.http.HttpServlet.service(HttpServlet.java:803)
note The full stack trace of the root cause is available in the Apache Tomcat/6.0.14 logs.
0
2011-6-5 16:07:11 org.apache.catalina.core.StandardWrapperValve invoke
严重: Servlet.service() for servlet Smima threw exception
java.lang.IndexOutOfBoundsException: Index: 0, Size: 0
at java.util.ArrayList.RangeCheck(Unknown Source)
at java.util.ArrayList.get(Unknown Source)
at service.XMima.Mima(XMima.java:13)
at Servlet.Smima.doGet(Smima.java:21)
at Servlet.Smima.doPost(Smima.java:31)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:710)
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 org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:233)
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:102)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:263)
at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:844)
at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:584)
at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:447)
at java.lang.Thread.run(Unknown Source)

解决方案 »

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XMiMa.java:
package service;
import org.hibernate.*;
import java.util.*;
import bean.Student;
import org.hibernate.cfg.Configuration;
import com.HibernateSessionFactory;
public class XMima {
    public boolean Mima(String XueHao,String YMm,String XMm){
    Session session=HibernateSessionFactory.getSession();
    Query query=session.createQuery("from Student where Sno='"+XueHao+"'");
    List list=query.list();
    System.out.println(list.size());
    Student stu=(Student)list.get(0);
    System.out.println(stu.getClassno());
    if(YMm.equals(stu.getSmima()))
     return true;
    else
     return false;
    }
}
Smima.java:
package Servlet;
import service.XMima;
import java.io.IOException;
import java.io.PrintWriter;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;public class Smima extends HttpServlet { public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {

response.setContentType("text/html");
PrintWriter out = response.getWriter();
String XueHao =(String)request.getSession().getAttribute("XueHao");
String YMm = request.getParameter("YMm");
String XMm = request.getParameter("XMm");
XMima dao=new XMima();
if(dao.Mima(XueHao, YMm , XMm))
response.sendRedirect("StuChenJi.jsp?XueHao= <%=XueHao%>");
else
response.sendRedirect("Index.jsp");
} public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
doGet(request,response);
}}
StuMima.jsp:
<%@ page language="java" import="java.util.*" pageEncoding="utf-8"%><%
String path = request.getContextPath();
String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
%><!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
  <head>
    <base href="<%=basePath%>">

    <title>学生课程系统</title>

<meta http-equiv="pragma" content="no-cache">
<meta http-equiv="cache-control" content="no-cache">
<meta http-equiv="expires" content="0">
<meta http-equiv="keywords" content="keyword1,keyword2,keyword3">
<meta http-equiv="description" content="This is my page">
  </head>

  <body>
    <style type="text/css">
    
    </style>
    <div id="header">
      <div id="header1";>
        <h1>学生信息系统</h1>
      </div>
      <div id="header2";>
        <h4><a href="Index.jsp">注销</a></h4>
      </div>
    </div>
    <div id="centers">
      <div class="c_left">
        <%String XueHao = request.getParameter("XueHao");
          out.print(""+XueHao+"");
        %>
        <li><a href="StuXuanKe.jsp?XueHao= <%=XueHao%>">选课</a></li>
        <li><a href="StuTuiKe.jsp?XueHao= <%=XueHao%>">退课</a></li>
        <li><a href="StuChenJi.jsp?XueHao= <%=XueHao%>">查询成绩</a></li>
        <li><a href="StuMiMa.jsp?XueHao= <%=XueHao%>">修改密码</a></li>
      </div>
      <div class="c_right">

        <%
          out.println("<form action='Smima' method='post'></br>");
          session.setAttribute("XueHao",XueHao);
          out.println("<h2>更改密码</h2></br>");
          out.println("原密码<input type=text name='YMm'></br>");
          out.println("现密码 <input type=text name='XMm'></br>");
          out.println("<input type=submit value='更改'></br>");
          out.println("</form>");

      %>

      </div>
    </div>
  </body>
</html>
找到问题了前面传数据  <li><a href="StuMiMa.jsp?XueHao=<%=XueHao%>">修改密码</a></li>  写成了 <li><a href="StuMiMa.jsp?XueHao= <%=XueHao%>">修改密码</a></li>   导致传导的原数据20080001变成了 20080001多了一个空格，不能与数据库里的数据匹配
Student stu=(Student)list.get(0);
list 为空或者没有装东东，你获取第一个元素可定就报这个异常呀，你要判断一下是否符合你的使用条件呀边界值问题。