//General
Request URL:http://127.0.0.1:8000/login
Request Method:GET
Status Code:200 OK
Remote Address:127.0.0.1:8000
Referrer Policy:no-referrer-when-downgrade
//Request Header
Accept:text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,*/*;q=0.8
Accept-Encoding:gzip, deflate, sdch, br
Accept-Language:zh-CN,zh;q=0.8
Cache-Control:max-age=0
Connection:keep-alive
Cookie:sessionid=r0jh6t92zbj3irmvy923ue2ts6x56zlc; csrftoken=7FWNJDLHdtc8RkM72U25q2zPcdpYv2S8f5SIjJoGxBi7dLkjPUB4hY2AXtfIi51D;
Host:127.0.0.1:8000
Upgrade-Insecure-Requests:1
User-Agent:Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/58.0.3029.110 Safari/537.36 SE 2.X MetaSr 1.0

HTTP无状态：无状态是指协议对于事务处理没有记忆能力，服务器不知道客户端是什么状态。从另一方面讲，打开一个服务器上的网页和之前打开这个服务器上的网页之间没有任何联系。
优点：服务器不用为每个客户端连接分配内存来记忆大量状态，也不用在客户端失去连接时去清理内存，以更高效地去处理WEB业务
缺点：客户端的每次请求都需要携带相应参数，服务器需要处理这些参数容易犯的误区：
1、HTTP是一个无状态的面向连接的协议，无状态不代表HTTP不能保持TCP连接，更不能代表HTTP使用的是UDP协议（无连接）
2、从HTTP/1.1起，默认都开启了Keep-Alive保持连接特性，简单地说当一个网页打开完成后，客户端和服务器之间用于传输
HTTP数据的TCP连接不会关闭，如果客户端再次访问这个服务器上的网页，会继续使用这一条已经建立的连接
3、Keep-Alive不会永久保持连接，它有一个保持时间，可以在不同的服务器软件（如Apache）中设定这个时间

//General
Request URL:http://127.0.0.1:8000/login
Request Method:GET
Status Code:200 OK
Remote Address:127.0.0.1:8000
Referrer Policy:no-referrer-when-downgrade
//Request Header
Accept:text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,*/*;q=0.8
Accept-Encoding:gzip, deflate, br
Accept-Language:zh-CN,zh;q=0.8
Cache-Control:max-age=0
Connection:keep-alive
Content-Length:17
Content-Type:application/x-www-form-urlencoded
Cookie:sessionid=r0jh6t92zbj3irmvy923ue2ts6x56zlc; csrftoken=7FWNJDLHdtc8RkM72U25q2zPcdpYv2S8f5SIjJoGxBi7dLkjPUB4hY2AXtfIi51D;
Host:127.0.0.1:8000
Origin:http://127.0.0.1:8000
Referer:http://127.0.0.1:8000/login
Upgrade-Insecure-Requests:1
User-Agent:Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/58.0.3029.110 Safari/537.36 SE 2.X MetaSr 1.0
//Form Data
user:root
pwd:123

//General
Request URL:http://127.0.0.1:8000/login
Request Method:GET
Status Code:200 OK
Remote Address:127.0.0.1:8000
Referrer Policy:no-referrer-when-downgrade
//Response Headers
Content-Length:322
Content-Type:text/html; charset=utf-8   //响应体使用utf-8编码
Date:Fri, 31 May 2019 06:36:42 GMT
Server:WSGIServer/0.2 CPython/3.7.0
X-Frame-Options:SAMEORIGIN

def login(req):print(req.COOKIES)if req.method == 'POST':user = req.POST.get('user')pwd = req.POST.get('pwd')if user == 'zhangsan' and pwd == '123':ret = redirect('index')ret.set_cookie('username',user)  #给index主页设置特定的缓存信息return retreturn render(req, 'login.html')def index(req):name = req.COOKIES.get('username', None)if  name: #如果访问主页时携带指定缓存，即成功登录过，那么后续可直接进入主页return render(req,'index.html',{'username':name})else:  #如果访问主页时未携带指定缓存，则跳转到登陆页面return redirect('login')

<!--登录页面-->
<form action="login" method="post"><p>姓名 <input type="text" name="user"></p><p>密码 <input type="password" name="pwd"></p><p><input type="submit"></p>
</form>
<!--登录后主页-->
<h2>登录后主页,欢迎{{ username }}登录</h2>

def login(req):print(req.COOKIES)print(req.session)if req.method == 'POST':user = req.POST.get('user')pwd = req.POST.get('pwd')req.session['iflogin'] = Truereq.session['username'] = userreturn redirect('index')return render(req, 'login.html')def index(req):name = req.session.get('username',None)if  name: return render(req,'index.html',{'username':name})else:  return redirect('login')