几乎相同的 deal.jsp 代码（index.jsp不变），在IDEA相同项目运行，结果却不一样，实在想不出来

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主要问题
主要项目
index.jsp:
deal.jsp（正确可运行）:
deal.jsp（错误不可运行）:
错误的代码运行图片：
可运行的代码运行图片

主要问题

几乎相同的 deal.jsp 代码（index.jsp不变），在IDEA相同项目相互运行，结果却不一样，实在想不出来

主要项目

对应的IDEA JSP项目:6.9_2.zip

index.jsp:

<%@ page contentType="text/html;charset=UTF-8" language="java" %><html><head><title>显示历史、显示添加留言功能</title> <link rel="stylesheet" type="text/css" href="word_index.css" /> <script language="JavaScript"> function ifNull(form_Msg){ var userName = form_Msg.upload_UserName.value; var userMsg = form_Msg.upload_UserMsg.value; if (userName === "") { alert("留言人不能为空"); form_Msg.upload_UserName.focus(); return false; } if (userMsg === "") { alert("留言内容不能为空"); form_Msg.upload_UserMsg.focus(); return false; } } </script></head><body><span class="word_Msg">留言板</span><br><br><% if (session.isNew()){ int number_person_index = 0; session.setAttribute("number_person",number_person_index); } int i; String[] message_index = (String[])session.getAttribute("message"); int num = Integer.parseInt(session.getAttribute("number_person").toString()); if (num != 0) { out.println("123213132"); out.println("number_person: " + num + "<br><br>"); for (i=0; i < num; i++) { out.println(message_index[i]); } }%><br><hr><form action="deal.jsp" id="form_UploadMassage" name="form_UploadMassage" method="post" onSubmit="return ifNull(form_UploadMassage)"> <span class="word_Msg">添加留言区域</span><br> 留言人：<input type="text" id="upload_UserName" name="upload_UserName" title="留言人"> 留言内容：<textarea id="upload_UserMsg" name="upload_UserMsg" title="留言内容"></textarea> <input name="Submit" type="submit" value="提交留言"> <input name="Submit2" type="reset" value="重置"></form></body></html>

deal.jsp（正确可运行）:

<%@ page language="java" contentType="text/html; charset=utf-8" pageEncoding="utf-8"%><% request.setCharacterEncoding("utf-8"); String userName_deal=request.getParameter("upload_UserName"); //获取留言人 String userMsg_deal=request.getParameter("upload_UserMsg"); //获取留言内容 String message_add="["+userName_deal+"]说："+userMsg_deal+"<br>"; //组合留言信息 int i; int num = Integer.parseInt(session.getAttribute("number_person").toString()); int num_add = num+1; String[] message_old = (String[])session.getAttribute("message"); String[] message_new = new String[num_add+1]; if(session.getAttribute("number_person")!=null){ if (num > 0) { for (i=0; i<num; i++) { message_new[i] = message_old[i]; } } message_new[num_add-1] = message_add; } session.setAttribute("number_person",num_add); session.setAttribute("message",message_new); //将留言信息保存到session中 response.sendRedirect("index.jsp");%>

deal.jsp（错误不可运行）:

<%@ page language="java" contentType="text/html; charset=utf-8" pageEncoding="utf-8"%><% request.setCharacterEncoding("utf-8"); String userName_deal = request.getParameter("upload_UserName"); String userMsg_deal = request.getParameter("upload_UserMsg"); String message_add = "["+userName_deal+"]说："+userMsg_deal+"<br>"; //组合留言信息 int i; int num = Integer.parseInt(session.getAttribute("number_person").toString()); int num_add = num+1; String[] message_old = (String[])session.getAttribute("message"); String[] message_new = new String[num_add+1]; if (session.getAttribute("number_person")!=null) { if (num > 0) { for (i=0; i<num; i++) { message_new[i] = message_old[i]; } } message_new[num_add-1] = message_add; } session.setAttribute("number_person",num_add); session.setAttribute("massage",message_new); response.sendRedirect("index.jsp");%>