Cookie实例——记住用户名

小鱼儿 2022-06-18 09:20 208阅读 0赞

## 1.简单流程图 ##

在网站登录中经常会有 记住用户名 这一操作，利用Cookie便可以实现，其间单的流程如下

![Center][]

## 2.利用代码实现 ##

新建一个Login的Servelet，写入下面代码

public void doGet(HttpServletRequest request, HttpServletResponse response)
    			throws ServletException, IOException {
    		response.setContentType("text/html;charset=UTF-8");
    		PrintWriter out = response.getWriter();
    		String userName ="";
    		String checked = "";
    		//得到客户端保存的Cookie数据
    		Cookie[] cookies = request.getCookies();
    		for (int i = 0;cookies!=null && i < cookies.length; i++) {
    			if("userName".equals(cookies[i].getName())){
    				userName = cookies[i].getValue();
    				checked = "checked='checked'";
    			}
    		}
    		
    		out.write("<form action='"+request.getContextPath()+"/servlet/DoLogin' method='post'>");
    		out.write("用户名：<input type='text' name='userName' value='"+userName+"'/><br/>");
    		out.write("密码：<input type='password' name='pwd'/><br/>");
    		out.write("<input type='checkbox' name='remember' "+checked+" />记住用户名<br/>");
    		out.write("<input type='submit' value='登录'/><br/>");
    		out.write("</form>");
    	}

再新建一个DoLogin方法

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();
    		//获取表单数据
    		String userName = request.getParameter("userName");
    		String pwd = request.getParameter("pwd");
    		String remember = request.getParameter("remember");
    		
    		Cookie ck = new Cookie("userName", userName);
    		ck.setPath("/");
    		//处理业务逻辑
    		//分发转向
    		if("tom".equals(userName)&&"123".equals(pwd)){
    			if(remember!=null){
    				ck.setMaxAge(Integer.MAX_VALUE);//设置Cookie的有效保存时间
    			}else{
    				ck.setMaxAge(0);//删除 Cookie
    			}
    			response.addCookie(ck);//将Cookie写回到客户端
    			out.write("登录成功！");
    		}else{
    			out.write("登录失败！");
    			//设置2秒跳到重新登录
    			response.setHeader("refresh", "2;url="+request.getContextPath()+"/servlet/Login");
    		}

得到的结果为：

![Center 1][]

登录后显示成功登录

再次访问时，“用户名”和“登录用户名”均自动填充

![Center 2][]

## 3.总结 ##

以上便是利用Cookie的知识来实现的一个网站经常拥有的功能，如果有错误，请提出，谢谢。

[Center]: /images/20220618/854eb82e50a743d683ed26424bc02570.png
[Center 1]: /images/20220618/97842a767236423abbb90d4f7d43c844.png
[Center 2]: /images/20220618/76308afe694847ff97d7652797959dfc.png