登录页面：login.jsp
<body>
<%--本页面提供登录表单，还要显示错误信息 --%>
<h1>登录</h1>
<%
String uname ="";
Cookie[] cs = request.getCookies();
if(cs!=null){
for(Cookie c:cs){
if("uname".equals(c.getName()))
{
uname=c.getValue();
}
}
}
%>
<%
String message="";
String msg = (String)request.getAttribute("msg");
if(msg!=null){
message = msg;
}
%>
<font color="red"><b><%=message %></b></font>
<form action="/hellosession1/LoginServlet" method="post">
用户名：<input type="text" name="username" value="<%=uname%>"><br>
密 码：<input type="password" name="password"><br>
<input type="submit" value="登录">
</form>
</body>
servlet处理页面：LoginServlet.java
throws ServletException, IOException {
//处理编码问题
request.setCharacterEncoding("UTF-8");
String username = request.getParameter("username");
String password = request.getParameter("password");
//校验用户名和密码是否正确
if(!"itcast".equalsIgnoreCase(username)){//登陆成功
Cookie cookie = new Cookie("uname",username);//获取cookie
cookie.setMaxAge(60*60*24);
response.addCookie(cookie);
HttpSession session = request.getSession();//获取session
session.setAttribute("username", username);//向session域中存username
response.sendRedirect("/hellosession1/session2/succ1.jsp");
}else{//登录失败
//如果失败，保存到request域中，转发到login.jsp
request.setAttribute("msg", "用户名或密码错误");
request.getRequestDispatcher("/session2/login.jsp").forward(request, response);
}
}
登录成功页面：succ1.jsp
<body>
<%
String username = (String)session.getAttribute("username");
if(username==null){
request.setAttribute("msg", "您还没有登录，请先登录!");
request.getRequestDispatcher("/session2/login.jsp").forward(request, response);
return;
}
%>
<h1>登录成功</h1>
欢迎回来<%=session.getAttribute("username") %>
</body>