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簡(jiǎn)單的驗(yàn)證跳轉(zhuǎn)

2020-3-6 seo達(dá)人

一.有關(guān)于內(nèi)置對(duì)象的作用域

主要說(shuō)明2個(gè)對(duì)象，request，session

1、request 對(duì)象

request 對(duì)象是 javax.servlet.httpServletRequest類型的對(duì)象。該對(duì)象代表了客戶端的請(qǐng)求信息，主要用于接受通過(guò)HTTP協(xié)議傳送到服務(wù)器的數(shù)據(jù)。（包括頭信息、系統(tǒng)信息、請(qǐng)求方式以及請(qǐng)求參數(shù)等）。

request只在2個(gè)頁(yè)面之間傳遞，每一次新的請(qǐng)求都會(huì)新建一個(gè)request對(duì)象，也就是說(shuō)可能會(huì)request對(duì)象不一致導(dǎo)致空指針異常。

2、session 對(duì)象

session 對(duì)象是由服務(wù)器自動(dòng)創(chuàng)建的與用戶請(qǐng)求相關(guān)的對(duì)象。服務(wù)器為每個(gè)用戶都生成一個(gè)session對(duì)象，用于保存該用戶的信息，跟蹤用戶的操作狀態(tài)。session對(duì)象內(nèi)部使用Map類來(lái)保存數(shù)據(jù)，因此保存數(shù)據(jù)的格式為 “Key/value”。 session對(duì)象的value可以使復(fù)雜的對(duì)象類型，而不僅僅局限于字符串類型。

session對(duì)象在整個(gè)會(huì)話只有一個(gè)，也就是說(shuō)session對(duì)象的數(shù)據(jù)會(huì)一直保留直到主動(dòng)進(jìn)行數(shù)據(jù)更改。

二.表單提交

在index.jsp中使用form進(jìn)行數(shù)據(jù)的提交，action的目標(biāo)是check.jsp，method是post

三.驗(yàn)證跳轉(zhuǎn)

當(dāng)form提交信息后交給check.jsp驗(yàn)證，使用getParameter來(lái)得到form的信息，并使用setAttribute保存。在check.jsp中判斷賬號(hào)密碼是否正確后，使用

<jsp:forward page=".jsp"></jsp:forward>

1

進(jìn)行跳轉(zhuǎn)，.jsp是想要跳轉(zhuǎn)的頁(yè)面路徑。

四.詳細(xì)代碼

index.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>登陸</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>

<form action="check.jsp" method="post">

請(qǐng)輸入用戶名：

<input type = "text" name = "username"><br/>

請(qǐng)輸入密碼：

<input type = "password" name = "passwd"><br/>

<input type="submit" name="submit" value="登錄">

</form>

</body>

</html>

check.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>驗(yàn)證</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>

<%

String username = (String)request.getParameter("username");

String passwd = (String)request.getParameter("passwd");

request.setAttribute("username", username);

request.setAttribute("passwd", passwd);

if(username.equals("admin")&&passwd.equals("123")){

%>

<jsp:forward page="succeed.jsp"></jsp:forward>

<%}else{ %>

<jsp:forward page="failed.jsp"></jsp:forward>

<%} %>

</body>

</html>

succeed.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>登陸成功</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>

<%

String username = (String)request.getAttribute("username");

String passwd = (String)request.getAttribute("passwd");

%>

<%=username %>登陸成功

</body>

</html>

failed.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>登陸失敗</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>

<%

String username = (String)request.getAttribute("username");

String passwd = (String)request.getAttribute("passwd");

%>

<%=username %>登陸失敗

</body>

</html>

五.注意事項(xiàng)

在jsp中使用form提交表單不能直接進(jìn)行跳轉(zhuǎn)，否則操作不慎就容易出現(xiàn)空指針異常，建議交由單獨(dú)的跳轉(zhuǎn)頁(yè)面處理