JavaWeb------cookie,session

On the

• cookie: client technology (response request)
• session: server technology, the use of this technology, you can save the user's session information? We can put information or data in the Session!

        cookie.getName(); //获得cookie中的key
        cookie.getValue(); //获得cookie中的vlaue
        new Cookie("lastLoginTime", System.currentTimeMillis()+""); //新建一个cookie
        cookie.setMaxAge(24*60*60); //设置cookie的有效期
        resp.addCookie(cookie); //响应给客户端一个cookie

cookie: usually stored in the local user directory appdata;

• A Cookie can only save a message;
• A web site can send multiple cookie to the browser, cookie store up to 20;
• Cookie size is limited 4KB;
• 300 browser cookie limit

encode decode

URLEncoder.encode("秦疆","utf-8")
URLDecoder.decode(cookie.getValue(),"UTF-8")

What is Session:

• Server will give each user (browser) to create a Seesion objects;
• A Seesion exclusively a browser, as long as the browser is not closed, the Session there;
• After the user logs in, it can access the entire site! -> Save user information; save the cart information ......

Session and cookie difference:

• Cookie is the user data addressed to the user's browser, the browser stores (can save more)
• Session data is written to the user's user exclusive Session, the server-side save (save important information, reduce waste server resources)
• Session object is created by the service;

scenes to be used:

• Save a user's login information;
• Shopping Cart information;
• Data is often used throughout the site, we will save it in the Session;

Session automatically expires: web.xml configuration

<!--设置Session默认的失效时间-->
<session-config>
<!--15分钟后Session自动失效，以分钟为单位-->
<session-timeout>15</session-timeout>
</session-config>