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

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" %>



    

    


留言板


<%

    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 + "

");
        for (i=0; i < num; i++) {
            out.println(message_index[i]);
        }
    }
%>




    添加留言区域

    留言人：
    留言内容：
    
    

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+"
"; //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

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+"
";   //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

错误的代码运行图片：

可运行的代码运行图片