Cookie 和Session

Posted 2020-12-04 legion

1Cookie 的概念

Cookie就是若干组键值对。

服务器在响应头中以如下格式设置cookie

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浏览器将cookie存储在本地，在以后的访问中，在请求中以如下形式发给服务器

关键API

服务器写Cookie

Cookie c=new Cookie("id", "the id is legion");
esponse.addCookie(c);
//多个依次重复

服务器读cookie

//从请求头中获取cookie数组
Cookie[] cs=request.getCookies();
//对于数组中每一个Cookie，有getName 和getValue的方法
//分别获取键和值

例子：本例子AServlet写若干cookie，其中一个cookie有key为”id“，

BServlet试图读取该id 的值。

//AServlet Get
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        // TODO Auto-generated method stub
        response.setContentType("text/html;charset=utf-8");
        Cookie c=new Cookie("id", "the id is legion");
        response.addCookie(c);
        Cookie c2=new Cookie("something", "sskalsa");
        response.addCookie(c2);
        response.getWriter().print("i sent you an id in cookie");
        
    }

//BServlet Get
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        // TODO Auto-generated method stub
        response.setContentType("text/html;charset=utf-8");
        Cookie[] cs=request.getCookies();
        if(cs!=null) {
            for(Cookie c:cs) {
                if(c.getName().equals("id")) {
                    String str="获取ID的值为"+c.getValue();
                    response.getWriter().print(str);
                }
            }
        }
    }

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