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<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>登录</title>
<script type="text/javascript">
function check()
{
    var uid =document.getElementById("userid");
    if(uid.value =="")
        {
        alert("代码不能为空");
        return false;
}
    if(uform.password.value=="")
        {
        alert("密码不能为空");
        return false;
        }
    return true;
    }
</script>
</head>
<body>
<form id="uform" action ="yanzheng.jsp" method="post" onSubmit="return check();">
用户：<input id="userid" type="text" name="userid" width=30/>
密码：<input id="passeord" type="password" name="password" width=30/>
<input type="submit" value="登录" />
<a href ="zhuce.jsp">注册新用户</a>
</form>


</body>
</html>
<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>登录验证页</title>
</head>
<body>

<%
String strUserid =request.getParameter("userid");
String strPW =request.getParameter("password");
if(strUserid == null || strUserid.trim().length() == 0)
{
    response.sendRedirect("message.jsp?msgid=1");
}
else if(strPW == null || strPW.trim().length() == 0)
{
    response.sendRedirect("message.jsp?msgid=2");
}
else
{//查找用户信息
    Object obj=application.getAttribute(strUserid);
    if(obj!=null){
        String strUser=obj.toString();
        String[] user= strUser.split("#");
        
    String strUID =user[0];
    String strUsername =user[1];
    String strP =user[2];
    
    
        if(strPW.equals(strP))
        {
            out.print("欢迎"+strUsername+"登陆");
            //跳转到系统页面
            session.setAttribute("login",strUsername);
        }
        else
        {
            response.sendRedirect("message.jsp?msgid=3");
        }
        
    }
    else
    {
        response.sendRedirect("message.jsp?msgid=4");
    }
}
%><br><br>
<a href="liuyan.jsp">留言</a>
</body>
</html>
<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
    <%@page import="java.util.*" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>消息页面</title>
</head>
<body>
<%
String strMsgId =request.getParameter("msgid");
if(strMsgId == null || strMsgId.trim().length()==0)
{
    out.print("信息错误");
}
else
{
    int iMsgid = Integer.parseInt(strMsgId);
    switch (iMsgid)
    {
    case 1:
        out.print("账号输入错误");
    break;
    case 2:
        out.print("密码输入错误");
    break;
    case 3:
        out.print("密码错误");
    break;
    case 4:
        out.print("用户不存在");
    break;
    case 5:
        out.print("请正确输入用户名");
    break;
    case 6:
        out.print("提交成功");
    break;
    case 7:
        out.print("用户代码已存在");
    break;
    case 8:
        out.print("用户未登录");
    break;
    default:
        out.print("无法识别信息");
        break;
    }
}
response.setHeader("refresh","3;URL=Login.jsp");

%>
</body>
</html>
<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>Insert title here</title>
</head>
<body>
<%
String strUserid =request.getParameter("userid");
String strUsername =request.getParameter("username");
String strPW =request.getParameter("password");
if(strUserid == null || strUserid.trim().length() == 0)
{
    response.sendRedirect("message.jsp?msgid=1");
}
else if(strUsername == null || strUsername.trim().length() == 0)
{
    response.sendRedirect("message.jsp?msgid=5");
}else if(strPW == null || strPW.trim().length() == 0)
{
    response.sendRedirect("message.jsp?msgid=2");
}
else
{//查找用户信息
    
    Object obj=application.getAttribute(strUserid);
    if(obj!=null){
        response.sendRedirect("message.jsp?msgid=7");
    }
    else{
    strUsername=new String(strUsername.getBytes("ISO-8859-1"),"UTF-8");
    String strUser=strUserid+"#"+strUsername+"#"+strPW;
    application.setAttribute(strUserid,strUser);
    response.sendRedirect("message.jsp?msgid=6");
    }
}
%>
</body>
</html>
<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>Insert title here</title>
<script type="text/javascript">
function check()
{
    var uform =document.getElementById("userid");
    if(uform.userid.value =="")
        {
        alert("代码不能为空");
        return false;
}
    if(uform.username.value =="")
    {
    alert("名称不能为空");
    return false;
}
    if(uform.password.value=="")
        {
        alert("密码不能为空");
        return false;
        }
    if(uform.password.value!=uform.queren.value)
    {
    alert("密码不一致");
    return false;
    }
    return true;
    }
</script>
<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
    <%@page import="java.util.*" %>
    <%@page import="java.text.*" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>留言</title>
<%
String userName ="";
//检查登录状态
Object o =session.getAttribute("login");
if(o == null)
{
    response.sendRedirect("message.jsp?msgid=8");
}
else
{
    userName = o.toString();
}

String liuyan=request.getParameter("liuyan");
if(liuyan != null && liuyan.equals(""))
{
     
    String strLiuyan=new String(liuyan.getBytes("ISO-8859-1"),"UTF-8");
    //附加时间信息
    Date dt = new Date();
    //格式化时间
    SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
    strLiuyan += "&nbsp;&nbsp; &nbsp; &nbsp;     "+sdf.format(dt)+"留言人:"+userName;
    Object obj = application.getAttribute("liuyan");
    ArrayList<String> a;
    if(obj==null)
    {
     a = new ArrayList<String>();
    
    }
    else
    {
         a  = (ArrayList<String>)obj;
        
    }
    a.add(strLiuyan);
    application.setAttribute("liuyan", a);
}
else
{
    
}
%>
</head>
<body>
<form >
最新留言：<br>
<%
int i =1;
    
    Object obj = application.getAttribute("liuyan");
    if(obj !=null)
    {
        ArrayList<String> a = (ArrayList<String>)obj;
for(int m = a.size()-1; m>=0;m-- )
{
    out.print(i+". "+a.get(m)+"<br>");
    i++;
}
    }
%>

请留言<br>
<textarea rows="10" cols="50" name="liuyan"></textarea>
<br>
<input type=submit value="提交">
</form>
</body>
</html>
</script>
</head>
<body>
<form id="uform" action="saveUser.jsp" method="post" onSubmit="return check();">
用户代码：<input id="userid" type="text" name="userid" width=30/><br><br>
用户名称：<input id="username" type="text" name="username" width=30/><br><br>
登录密码<input id="password" type="password" name="password" width=30/><br><br>
确认密码：<input id="queren" type="password" name="queren" width=30/><br><br>
<input type="submit" value="提交"/>
</body>
</html>
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原文地址：https://www.cnblogs.com/zhuxiaolin/p/5005937.html