cookie记录用户名和密码

getAttribute和getParameter的区别：

request.getAttribute():是request时设置的变量的值,用request.setAttribute("name","您自己的值");来设置值,
request.getParameter():提取发送过来的参数如:本网页

登录页面 login.java

public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
request.setCharacterEncoding("UTF-8");
response.setContentType("text/html;charset=UTF-8");
PrintWriter out = response.getWriter();
//判断是否是错误
String error = (String)request.getAttribute("error");
System.out.println("---error---"+ error);

//拿到客户端携带的所有的cookie
String username = "";
String password = "";
//拿到所有的cookie
Cookie[] cs = request.getCookies();
for (int i = 0;cs != null && i < cs.length; i++) {
Cookie c = cs[i];
if(c.getName().equals("name")){
username = c.getValue();
System.out.println("拿到了cookie的用户名" + username);
}
if(c.getName().equals("password")){
password = c.getValue();
System.out.println("拿到了cookie的密码" + password);
}

}
//创建页面
out.write("登录页面<br>");
if(error != null){
out.write("<font color=red>" + error +"</font><br>");
}
out.write("<form action='" + request.getContextPath() + "/servlet/rember' method='post' >");
out.write("姓名：<input type='text' name='username' value='"+ username +"'><br><br> ");
out.write("密码：<input type='password' name='password' value='"+ password +"'><br> ");
out.write("<input type='checkbox' name='remember' value='on'>记住用户名和密码两周<br> ");
out.write("<input type='submit' value='登录'><br> ");
out.write("</form>");

}

 处理数据页面：

rember.java

public void doGet(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {

        request.setCharacterEncoding("UTF-8");
        response.setContentType("text/html;charset=UTF-8");
        PrintWriter out = response.getWriter();
        //拿到浏览器传递的数据
        String name = request.getParameter("username");
        String password = request.getParameter("password");
        String remember = request.getParameter("remember");
        System.out.println("----username------" + name);
        System.out.println("----password------" + password);
        System.out.println("----remember------" + remember);
        
        //判断数据，用户名=密码的逆序
        String repassword = new StringBuffer(password).reverse().toString();
        if(name.equals(repassword)){
            //合法用户
            //判断是否需要记住
            if("on".equals(remember)){
                Cookie c1 = new Cookie("name",name);
                Cookie c2 = new Cookie("password",password);
                c1.setMaxAge(Integer.MAX_VALUE);
                c2.setMaxAge(Integer.MAX_VALUE);
                //设定访问路径
                c1.setPath(request.getContextPath());
                c2.setPath(request.getContextPath());
                //向客户端发送Cookie
                response.addCookie(c1);
                response.addCookie(c2);            }
            
            request.setAttribute("name", name);
            request.getRequestDispatcher("main").forward(request, response);
        }else{
            //非法用户
            request.setAttribute("error", "用户名或者密码错误");
            request.getRequestDispatcher("login").forward(request, response);
        }
    }

登录后的主页面：

    public void doGet(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {

        request.setCharacterEncoding("UTF-8");
        response.setContentType("text/html;charset=UTF-8");
        PrintWriter out = response.getWriter();
        String name = (String)request.getAttribute("name");
        System.out.println("---main----name----"+name);
        out.write("欢迎回来 " + name);
    }

登录，输入用户名和密码，如果勾选了记住用户名和密码选项，则将用户名和密码放到cookie中，下次登录则获取cookie中的用户名和密码；

如果用户名和密码错误，则将错误信息通过request对象发送回客户端。