cookie与session

continueLR

已于 2022-01-27 23:16:43 修改

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分类专栏： JavaWeb 文章标签： elementui html webview

于 2022-01-27 23:16:18 首次发布

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第一章：cookie与session的使用

1.cookie的使用

1：在index.jsp做一个登录表单作为login请求

 <h1>登录</h1>
  <form action="login" method="post">
    用户名:<input type="text" name="username" value="${unamecookie}"><br>
    密码：<input type="password" name="pass"><br>
    <input type="submit" value="登录">
  </form>

2：创建servlet处理类处理login请求

package servlet;

import javax.servlet.ServletException;
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 java.io.IOException;

@WebServlet(urlPatterns = "/login")
public class loginServlet extends HttpServlet {
    @Override
    protected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        //接参数
        String username = req.getParameter("username");
        String pass = req.getParameter("pass");
        //写逻辑：判断正误
        if ("admin".equals(username)&&"123456".equals(pass)){
            //登录成功
            resp.sendRedirect("success.jsp");
        }else{
            //登录失败
            //1.后台创建cookie
            Cookie cookie = new Cookie("uname",username);
            //2.返回给前端
            resp.addCookie(cookie);
            resp.sendRedirect("index.jsp");
        }
    }
}

3：前端使用cookie

<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
  <head>
    <title>$Title$</title>
  </head>
  <body>
  <%
    Cookie[] cookies = request.getCookies();
    String value="";
    if (cookies.length>0){//这个if判断避免因为遍历空数据而报错
      for (Cookie cookie : cookies) {//遍历cookies数组
        if (cookie.getName().equals("uname")){
          value = cookie.getValue();
          break;
        };
      }
    }
    pageContext.setAttribute("unamecookie",value);
  %>
  <h1>登录</h1>
  <form action="login" method="post">
    用户名:<input type="text" name="username" value="${unamecookie}"><br>
    密码：<input type="password" name="pass"><br>
    <input type="submit" value="登录">
  </form>
  </body>
</html>

2.session的使用

1.登录成功session存值，设置失效时间

package servlet;

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.*;
import java.io.IOException;

@WebServlet(urlPatterns = "/login")
public class loginServlet extends HttpServlet {
    @Override
    protected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        //接参数
        String username = req.getParameter("username");
        String pass = req.getParameter("pass");
        //写逻辑：判断正误
        if ("admin".equals(username)&&"123456".equals(pass)){
            //登录成功
            //session存值
            HttpSession session = req.getSession();
            session.setAttribute("username",username);
            session.setAttribute("psssword",pass);
            //设置session失效时间
            session.setMaxInactiveInterval(60*30);//单位是秒
            //重定向或者转发，session数据是不会丢失的，但重定向时，requet中的数据会丢失
            resp.sendRedirect("success.jsp");
        }else{
            //登录失败
            //1.后台创建cookie
            Cookie cookie = new Cookie("uname",username);
            //2.返回给前端
            resp.addCookie(cookie);
            resp.sendRedirect("index.jsp");
        }
    }
}

2.显示session

<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <title>Title</title>
</head>
<body>
<h1>testsession.jsp</h1>
当前登录用户:${sessionScope.username}<br>
</body>
</html>

3.退出清空session请求

<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <title>Title</title>
</head>
<body>
<h1>success.jsp</h1>
当前登录用户:${sessionScope.username}<br>
<a href="loginout">退出</a>
</body>
</html>

4.servlet处理类处理退出请求

package servlet;

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;

@WebServlet(urlPatterns = "/loginout")
public class LoginOutServlet extends HttpServlet {
    @Override
    protected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        req.getSession().invalidate();//使session失效
        resp.sendRedirect("index.jsp");
    }
}