login.jsp页面
<head>
<script type="text/javascript" src="js/captcha.js"></script>
<style type="text/css">
.code
{
background:url(code_bg.jpg);
font-family:Arial;
font-style:italic;
color:blue;
font-size:20px;
border:0;
padding:2px 3px;
letter-spacing:3px;
font-weight:bolder;
float:left;
cursor:pointer;
height:20px;
text-align:center;
vertical-align:middle;
}
a
{
text-decoration:none;
font-size:12px;
color:#288bc4;
}
a:hover
{
text-decoration:underline;
}
</style>
</head>
<body background="image/bk_login.jpg" id="form1" runat="server">
<%
String name = "";
String password = "";
Cookie[] cookies = request.getCookies();//获取请求中的所有cookie
if(cookies != null){
for(Cookie c : cookies){//循环遍历所有cookie
if(c.getName().equals("userName")){//查找名为userName的cookie
name = c.getValue();//获取这个cookie值，赋给name
}
if(c.getName().equals("userPass")){
password = c.getValue();
}
}
}
%>
<form action="LoginServlet" method="post" onsubmit="validateloginInput()">
<table>
<%
String error=(String)request.getAttribute("error");
if(error!=null){
out.println("<font color=‘red‘>"+error+"</font>");
}
%>
<tr>
<td>登陆名：</td>
<td> <input type="text" name="name" id="name" value="<%=name%>" onblur="LoginUserName()">
<span id="login01"></span>
</td>
</tr>
<tr>
<td>密码：</td>
<td><input type="password" name="password" id="password" value="<%=password%>" onblur="LoginUserPass()">
<span id="pass01"></span>
<br></td>
</tr>
<tr>
<td>
<div class="code" id="checkCode" onclick="createCode()" ></div>
</td>
<td>
<input style="float:left;width:80px;height:20px" placeholder="验证码"type="text" id="inputCode" name="inputCode" onchange="validateCode()" onblur="CheckCode()"/>
<input type="checkbox" name="remember" id="remeber">记住我
<span id="code01"></span>
</td>
</tr>
<tr>
<td><input name="identity" type="radio" value="admin" style="margin-left:30px">管理员</td>
<td><input name="identity" type="radio" value="user" style="margin-left:80px" checked="checked">用户</td>
</tr>
<tr>
<td style="padding-left:30px"><input type="submit" value="登录"></td>
</tr>
</table>
</form>
</body>
js文件夹下captcha.js
//在全局 定义验证码
var code;
function createCode()
{
code = "";
var codeLength = 6; //验证码的长度
var checkCode = document.getElementById("checkCode");
var codeChars = new Array(0, 1, 2, 3, 4, 5, 6, 7, 8, 9,
‘a‘,‘b‘,‘c‘,‘d‘,‘e‘,‘f‘,‘g‘,‘h‘,‘i‘,‘j‘,‘k‘,‘l‘,‘m‘,‘n‘,‘o‘,‘p‘,‘q‘,‘r‘,‘s‘,‘t‘,‘u‘,‘v‘,‘w‘,‘x‘,‘y‘,‘z‘,
‘A‘, ‘B‘, ‘C‘, ‘D‘, ‘E‘, ‘F‘, ‘G‘, ‘H‘, ‘I‘, ‘J‘, ‘K‘, ‘L‘, ‘M‘, ‘N‘, ‘O‘, ‘P‘, ‘Q‘, ‘R‘, ‘S‘, ‘T‘, ‘U‘, ‘V‘, ‘W‘, ‘X‘, ‘Y‘, ‘Z‘); //所有候选组成验证码的字符，当然也可以用中文的
for(var i = 0; i < codeLength; i++)
{
var charNum = Math.floor(Math.random() * 52);
code += codeChars[charNum];
}
if(checkCode)
{
checkCode.className = "code";
//把code值赋给验证码
checkCode.innerHTML = code;
}
}
function validateCode()
{
var inputCode=document.getElementById("inputCode").value;
if(inputCode.length <= 0)
{
document.getElementById("code01").innerHTML="<font color=‘red‘>请输入验证码！</font>"
}
else if(inputCode.toUpperCase() != code.toUpperCase())
{
document.getElementById("code01").innerHTML="<font color=‘red‘>验证码输入有误！</font>"
createCode();
document.getElementById("inputCode").value="";
}else{
document.getElementById("code01").innerHTML=""
}
}
后台登录的LoginServlet
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
//设置请求对象的字符编码,编码值与页面请求编码值一致，此处假设为UTF-8
request.setCharacterEncoding("UTF-8");
//获取参数，获取页面中名字为 method，把值为login的值取过来
String name=request.getParameter("name");
String password=request.getParameter("password");
String codecheck=request.getParameter("inputCode");
String remember=request.getParameter("remember");
String identity=request.getParameter("identity");
if("admin".equals(identity)){
if(name.length()==0||name==null||password.length()==0||password==null||codecheck==""){
request.getRequestDispatcher("login.jsp").forward(request, response);
}
Admin admin=adminService.login(name,password);
if(admin==null){
request.setAttribute("error","您输入的用户名或密码有误！");
request.getRequestDispatcher("login.jsp").forward(request, response);
}
else{
if(codecheck==""){
response.sendRedirect("login.jsp");
}else{
if(remember!=null){
//把用户名和密码存储到cookie里，下次可以直接登录
Cookie cookie = new Cookie("userName",name);// 新建一个Cookie对象
cookie.setMaxAge(24*60*60); // 设置过期时间1天，以秒为单位
response.addCookie(cookie);// 保存cookie到客户端
cookie = new Cookie("userPass",password);
cookie.setMaxAge(24*60*60);
response.addCookie(cookie);
}
request.getSession().setAttribute("Admin", admin);//Admin中存储当前登录成功的用户名密码信息，以便于在jsp页面中用EL表达式${Admin.getA_name()}将当前用户名显示出来
//服务器端跳转，可以将rquest中获取（存储）的值带到下一个界面
//登录成功后，下拉框里的值从数据库中获取展示到页面
List<Course> list=courseService.displayCourse();
//request表示一次请求，在传入adminindex.jsp页面后，request里的值会消失，session存储是在整个服务器中都可被调用
//request.setAttribute("list_displaycourse_name", list);
request.getSession().setAttribute("list_displaycourse_name", list);
request.getRequestDispatcher("adminindex.jsp").forward(request, response);
}
}
} else if("user".equals(identity)){
.........................
}
}
原文地址：https://www.cnblogs.com/97chen629/p/10669727.html