ly.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>
<body>
<table width="386" border="1" align="center">
<tr>
<td width="376" height="111">
<form id="form1" name="form1" method="post" action="doly.jsp"> <textarea name="textarea"></textarea> <input type="submit" name="Submit" value="提交" />
</form>
<p>
<label></label>
</p>
</td>
</tr>
<tr>
<td height="124">
<%
List list = (List)session.getAttribute("list");
if(list != null)
for(Object o : list)
{
{
%>
<table width="250" border="1" align="center">
<tr>
<td height="47">
<%=o %>
</td>
</tr>
</table>
<%}} %>
</td>
</tr>
</table>
</body>
</html>doly.jsp
<%@ page language="java" import="java.util.*" pageEncoding="utf-8"%>
<%@page import="javax.faces.application.Application"%>
<%
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> </head> <body>
<%
request.setCharacterEncoding("UTF-8");
String content = request.getParameter("textarea");
if (session.getAttribute("list") == null) {
List list = new ArrayList();
list.add(content);
session.setAttribute("list", list);
response.sendRedirect("ly.jsp");
} else {
List list = (List) session.getAttribute("list");
list.add(content);
response.sendRedirect("ly.jsp");
}
%>
</body>
</html>
1、我说下我认为的执行流程,先是单击ly.jsp中的提交按钮,跳转到doly.jsp中,然后通过判断后response.sendRedirect("ly.jsp");返回ly.jsp然后进行判断输出内容。以上说的有误请纠正下。
2、if (session.getAttribute("list") == null) {
List list = new ArrayList();
list.add(content);
session.setAttribute("list", list);
response.sendRedirect("ly.jsp");
}中,为什么list可以先拿来判断,后初始化呢??
<%@ 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>
<body>
<table width="386" border="1" align="center">
<tr>
<td width="376" height="111">
<form id="form1" name="form1" method="post" action="doly.jsp"> <textarea name="textarea"></textarea> <input type="submit" name="Submit" value="提交" />
</form>
<p>
<label></label>
</p>
</td>
</tr>
<tr>
<td height="124">
<%
List list = (List)session.getAttribute("list");
if(list != null)
for(Object o : list)
{
{
%>
<table width="250" border="1" align="center">
<tr>
<td height="47">
<%=o %>
</td>
</tr>
</table>
<%}} %>
</td>
</tr>
</table>
</body>
</html>doly.jsp
<%@ page language="java" import="java.util.*" pageEncoding="utf-8"%>
<%@page import="javax.faces.application.Application"%>
<%
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> </head> <body>
<%
request.setCharacterEncoding("UTF-8");
String content = request.getParameter("textarea");
if (session.getAttribute("list") == null) {
List list = new ArrayList();
list.add(content);
session.setAttribute("list", list);
response.sendRedirect("ly.jsp");
} else {
List list = (List) session.getAttribute("list");
list.add(content);
response.sendRedirect("ly.jsp");
}
%>
</body>
</html>
1、我说下我认为的执行流程,先是单击ly.jsp中的提交按钮,跳转到doly.jsp中,然后通过判断后response.sendRedirect("ly.jsp");返回ly.jsp然后进行判断输出内容。以上说的有误请纠正下。
2、if (session.getAttribute("list") == null) {
List list = new ArrayList();
list.add(content);
session.setAttribute("list", list);
response.sendRedirect("ly.jsp");
}中,为什么list可以先拿来判断,后初始化呢??
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便进入了if语句 LZ若是有疑问 你吧if语句改为:
if (session.getAttribute("list") != null) { 你看看他还会不会进去。
List list = new ArrayList();//这里的初始化是你自己从新new的,这两个list并非是同一个list,只是名字都是叫list而已。以后命名注意这一点,不要因为名字相同就是同一个
List list = new ArrayList();
list.add(content);
session.setAttribute("list", list);
}
response.sendRedirect("ly.jsp");
你的代码应该这样写吧,session在setAttribute前一般会先判断是否为空的,否则会覆盖之前的。还有你的这个应该不是用session而用request的吧?如果用request则可
List list = new ArrayList();
list.add(content);
request.setAttribute("list", list);
response.sendRedirect("ly.jsp");