cookie_session

一、cookie

解决中文乱码的问题：

        // 解决post请求中文乱码问题
        // 一定要在获取请求参数之前调用才有效
        req.setCharacterEncoding("UTF-8");
        // 解决响应中文乱码问题
        resp.setContentType("text/html; charset=UTF-8");

添加 cookie，保存在浏览器：
在浏览器的 applicatioin 项中可以查看。

    protected void createCookie(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        //1 创建Cookie对象
        Cookie cookie = new Cookie("key4", "value4");
        //2 通知客户端保存Cookie
        resp.addCookie(cookie);
        //1 创建Cookie对象
        Cookie cookie1 = new Cookie("key5", "value5");
        //2 通知客户端保存Cookie
        resp.addCookie(cookie1);

        resp.getWriter().write("Cookie创建成功");
    }

获得 cookie

    protected void getCookie(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        Cookie[] cookies = req.getCookies();
        for (Cookie cookie : cookies) {
            // getName方法返回Cookie的key（名）
            // getValue方法返回Cookie的value值
            resp.getWriter().write("Cookie[" + cookie.getName() + "=" + cookie.getValue() + "] 
");
        }
        Cookie iWantCookie = CookieUtils.findCookie("key1", cookies);
//        for (Cookie cookie : cookies) {
//            if ("key2".equals(cookie.getName())) {
//                iWantCookie = cookie;
//                break;
//            }
//        }
        // 如果不等于null，说明赋过值，也就是找到了需要的Cookie
        if (iWantCookie != null) {
            resp.getWriter().write("找到了需要的Cookie");
        }
    }

设置cookie的存活时间

• 参数为整数，则存活多少秒
• 参数为-1，则浏览器关闭，cookie立马删除
• 参数为0，表示立即删除

    /**
     * 默认的会话级别的Cookie
     *
     * @param req
     * @param resp
     * @throws ServletException
     * @throws IOException
     */
    protected void defaultLife(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        Cookie cookie = new Cookie("defalutLife", "defaultLife");
        cookie.setMaxAge(-1);//设置存活时间
        resp.addCookie(cookie);
    }

创建带有path的cookie

    protected void testPath(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        Cookie cookie = new Cookie("path1", "path1");
        // getContextPath() ===>>>>  得到工程路径
        cookie.setPath(req.getContextPath() + "/abc"); // ===>>>>  /工程路径/abc
        resp.addCookie(cookie);
        resp.getWriter().write("创建了一个带有Path路径的Cookie");
    }

使用 cookie 免用户名登录

package com.atguigu.servlet;

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

public class LoginServlet extends HttpServlet {

    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        String username = req.getParameter("username");
        String password = req.getParameter("password");

        if ("wzg168".equals(username) && "123456".equals(password)) {
            //登录 成功
            Cookie cookie = new Cookie("username", username);
            cookie.setMaxAge(60 * 60 * 24 * 7);//当前Cookie一周内有效
            resp.addCookie(cookie);
            System.out.println("登录 成功");
        } else {
//            登录 失败
            System.out.println("登录 失败");
        }
    }
}

二、session

创建session

    protected void createOrGetSession(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        // 创建和获取Session会话对象
        HttpSession session = req.getSession();
        // 判断 当前Session会话，是否是新创建出来的
        boolean isNew = session.isNew();
        // 获取Session会话的唯一标识 id
        String id = session.getId();
        resp.getWriter().write("得到的Session，它的id是：" + id + " 
 ");
        resp.getWriter().write("这个Session是否是新创建的：" + isNew + " 
 ");
    }

向session 域中存放数据

    /**
     * 往Session中保存数据
     *
     * @param req
     * @param resp
     * @throws ServletException
     * @throws IOException
     */
    protected void setAttribute(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        req.getSession().setAttribute("key1", "value1");
        resp.getWriter().write("已经往Session中保存了数据");

    }
    /**
     * 获取Session域中的数据
     *
     * @param req
     * @param resp
     * @throws ServletException
     * @throws IOException
     */
    protected void getAttribute(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        Object attribute = req.getSession().getAttribute("key1");
        resp.getWriter().write("从Session中获取出key1的数据是：" + attribute);
    }

session 中的默认的超时时长 30mins，可以设置

    protected void defaultLife(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        // 获取了Session的默认超时时长
        int maxInactiveInterval = req.getSession().getMaxInactiveInterval();
        resp.getWriter().write("Session的默认超时时长为：" + maxInactiveInterval + " 秒 ");
    }

    protected void life3(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        // 先获取Session对象
        HttpSession session = req.getSession();
        // 设置当前Session3秒后超时
        session.setMaxInactiveInterval(3);
        resp.getWriter().write("当前Session已经设置为3秒后超时");
    }

设置session失效

    protected void deleteNow(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        // 先获取Session对象
        HttpSession session = req.getSession();
        // 让Session会话马上超时
        session.invalidate();
        resp.getWriter().write("Session已经设置为超时（无效）");
    }

三、浏览器和Session之间关联的技术内幕

注销的逻辑其实就是把获得请求的 session,然后让其失效。
req.getSession().invalidate();