Cookie

Cookie

什么是 Cookie?

1. Cookie 翻译过来是饼干的意思。
2. Cookie 是服务器通知客户端保存键值对的一种技术。
3. 客户端有了 Cookie 后，每次请求都发送给服务器。
4. 每个 Cookie 的大小不能超过 4kb

如何创建 Cookie

servlet：

protected void createCookie(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        //1.创建cookie对象
        Cookie cookie = new Cookie("key1", "value1");
        //2.通知客户端保存cookie
        response.addCookie(cookie);
        response.getWriter().write("cookie创建成功！");
    }

服务器如何获取 Cookie

服务器获取客户端的 Cookie 只需要一行代码：req.getCookies():Cookie[]

public class CookieUtils {
    /**
     * 查找指定名称的Cookie 对象
     *
     * @param name
     * @param cookies
     * @return
     */
    public static Cookie findCookie(String name, Cookie[] cookies) {
        if (name == null || cookies == null || cookies.length == 0) {
            return null;
        }

        for (Cookie cookie : cookies) {
            if (name.equals(cookie.getName())) {
                return cookie;
            }
        }

        return null;
    }

}

Servlet：

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

        Cookie cookie = CookieUtils.findCookie("key1", request.getCookies());
        response.getWriter().write("Cookie[key:"+cookie.getName()+" value:"+cookie.getValue()+"]<br>");
    }

Cookie值的修改

方案一

1. 先创建一个要修改的同名（指的就是 key）的 Cookie 对象
2. 在构造器，同时赋于新的 Cookie 值。
3. 调用 response.addCookie( Cookie );

Cookie cookie = new Cookie("key1","newValue1");
resp.addCookie(cookie);

方案二

1. 先查找到需要修改的 Cookie 对象
2. 调用 setValue()方法赋于新的 Cookie 值。
3. 调用 response.addCookie()通知客户端保存修改

Cookie cookie = CookieUtils.findCookie("key2", req.getCookies());
if (cookie != null) 
	cookie.setValue("newValue2");
resp.addCookie(cookie);

Cookie生命控制

Cookie 的生命控制指的是如何管理 Cookie 什么时候被销毁（删除）

setMaxAge()

正数，表示在指定的秒数后过期

负数，表示浏览器一关，Cookie 就会被删除（默认值是-1）

零，表示马上删除 Cookie

protected void createCookie(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        //1.创建cookie对象
        Cookie cookie = new Cookie("key1", "value1");
        //2.通知客户端保存cookie
        response.addCookie(cookie);
        response.getWriter().write("cookie创建成功！");
    }

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

        Cookie cookie = CookieUtils.findCookie("key1", request.getCookies());
        response.getWriter().write("Cookie[key:"+cookie.getName()+" value:"+cookie.getValue()+"]<br>");
    }

    protected void updateCookie(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        Cookie cookie = new Cookie("key1","newValue1");
        response.addCookie(cookie);
    }

    protected void defaultLife(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        Cookie cookie = new Cookie("defaultLife", "defaultLife");
        cookie.setMaxAge(-1);
        response.addCookie(cookie);
    }

    protected void deleteNow(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        //找到要删除的cookie
        Cookie cookie = CookieUtils.findCookie("key1", request.getCookies());
        if(cookie!=null){
            //调用setMaxage
            cookie.setMaxAge(0);
            //addCookie
            response.addCookie(cookie);
        }
    }

    protected void life3600(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        Cookie cookie = new Cookie("life3600", "life3600");
        //设置一小时
        cookie.setMaxAge(3600);
        response.addCookie(cookie);
        response.getWriter().write("创建了一个一小时的cookie");
    }

Cookie有效路径 Path 的设置

Cookie 的 path 属性可以有效的过滤哪些 Cookie 可以发送给服务器。哪些不发。path 属性是通过请求的地址来进行有效的过滤。

请求地址如下：

http://ip:port/工程路径/a.html

• CookieA 发送
• CookieB 不发送

http://ip:port/工程路径/abc/a.html

• CookieA 发送
• CookieB 发送

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

Cookie练习—免输入用户名登录

login.jsp

<form action="http://localhost:8080/06_cookie_session/loginServlet" method="get">
    用户名：<input type="text" name="username" value="${cookie.username.value}"> <br>
    密码：<input type="password" name="password"> <br>
    <input type="submit" value="登录">
</form>

LoginServlet

protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        String username = request.getParameter("username");
        String password = request.getParameter("password");
        if ("admin".equals(username) && "admin".equals(password)) {
            //登录成功
            //当前Cookie 一周内有效resp.addCookie(cookie);
            Cookie cookie = new Cookie("username", username);
            cookie.setMaxAge(60 * 60 * 24 * 7);
            response.addCookie(cookie);
            System.out.println("登录 成功");
        } else {
            //登录失败
            System.out.println("登录 失败");
        }
    }