用Cookie记住上次登录用户名

时间：2022-05-25 07:05:54

一个登录页面设置查看Cookie中的数据（Cookie不为null）;然后将页面提交到另一个页面去，在这个页面中的到是否选择记住用户名，如果选择了，

就创建Cookie对象，将用户名存储起来，下次登录时，用户名直接显示在上面，注意：路径一定要一致，且都能访问。

登录页面

package com.itheima.cookie;

import java.io.IOException;

import java.io.PrintWriter;

import javax.servlet.ServletException;

import javax.servlet.annotation.WebInitParam;

import javax.servlet.annotation.WebServlet;

import javax.servlet.http.Cookie;

import javax.servlet.http.HttpServlet;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpServletResponse;

import com.itheima.myConstant;

//模拟登录时，记住用户名和密码

@WebServlet(

		urlPatterns = { "/CookieDemo2" },

		initParams = {

				@WebInitParam(name = "CookieDemo2", value = "com.itheima.cookie.CookieDemo2")

		})

public class CookieDemo2 extends HttpServlet {

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

		//读取记住的用户名

		String name="";

		String rem="";

		Cookie[] cookies=request.getCookies();

		for(int i=0;cookies!=null&&i<cookies.length;i++){

			Cookie c=cookies[i];

			if(myConstant.USER_NAME.equals(c.getName())){

				//找到了

				String value=c.getValue();

				name=value;

				rem="checked='checked'";

			}

		}

		//显示出登陆界面

		response.setContentType("text/html;charset=utf-8");

		PrintWriter out=response.getWriter();

		out.println("<html>");

		out.println("<head><title>用户登陆</title></head>");

		out.println("<body>");

		out.println("<form action='/CookieTest/CookieDemo3' method='post'>");

		out.println("<table width='400' border='1'>");

		out.println("<tr>");

		out.println("<td>用户名</td>");

		out.println("<td><input type='text' name='username' value="+name+"/></td>");

		out.println("</tr>");

		out.println("<tr>");

		out.println("<td>密码</td>");

		out.println("<td><input type='password' name='password'/></td>");

		out.println("</tr>");

		out.println("<tr>");

		out.println("<td colspan='2'><input type='checkbox' name='remember'"+rem+"/>记住用户名</td>");

		out.println("</tr>");

		out.println("<tr>");

		out.println("<td colspan='2'><input type='submit' value='go'/></td>");

		out.println("</tr>");

		out.println("</table></form></body></html>");

	}

	protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

	}

}

处理页面

package com.itheima.cookie;

import java.io.IOException;

import javax.servlet.ServletException;

import javax.servlet.annotation.WebInitParam;

import javax.servlet.annotation.WebServlet;

import javax.servlet.http.Cookie;

import javax.servlet.http.HttpServlet;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpServletResponse;

import com.itheima.myConstant;

/**

 * 接收用户名和密码，验证是否是合法用户

 *看用户是否选中了checkbox,如果选中，将数据写入Cookie

 */

@WebServlet(

		urlPatterns = { "/CookieDemo3" },

		initParams = {

				@WebInitParam(name = "CookieDemo3", value = "com.itheima.cookie.CookieDemo3")

		})

public class CookieDemo3 extends HttpServlet {

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

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

//		System.out.println(remember);//选中输出on，不选中输出null(value的值)

		if(remember!=null){

			//如果选中,把用户名写入Cookie

			Cookie c=new Cookie(myConstant.USER_NAME,request.getParameter("username"));

			c.setPath(request.getContextPath());

			c.setMaxAge(Integer.MAX_VALUE);//永久保存

			response.addCookie(c);

		}

		response.setContentType("text/html;charset=utf-8");

		response.getWriter().write("登陆成功，这是主页");

	}

	protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

		doGet(request,response);

	}

}

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