tornado框架学习
tornado是一个非阻塞的web服务器框架，每秒可以处理上千个客户端连接（都是在一个线程中，不需要为每个客户端创建线程，资源消耗少），适合用来开发web长连接应用，如long polling（轮询），WebSocket协议等（http协议为短连接）。
1，简单使用
#coding:utf-8
import tornado.ioloop
import tornado.web
from controllers.login import LoginHandler class HomeHandler(tornado.web.RequestHandler): #处理'/index'的请求，若是get请求，即调用get方法
def get(self, *args, **kwargs):
self.write('home page') settings = {
'template_path':'views' #配置html文件的目录，即html文件存储在views文件夹路径下
'static_path':'statics', # 配置静态url路径，用来存放css，js文件等
}
app = tornado.web.Application([
(r'/index',HomeHandler), # 路由分发器，HomeHandler为该路由的处理类
(r'/login',LoginHandler),
],**settings) #加入配置文件 if __name__ == '__main__':
app.listen(8080) #监听端口号
tornado.ioloop.IOLoop.instance().start() #开启服务器
上面代码即建立起一个web服务器，在浏览器输入127.0.0.1:8080/index， 就会得到包含‘home page’字符的网页。另外，上面将所有代码写在了有个代码文件中，也可以利用MVC的设计方式分开来写，如下面的的架构和代码：将处理‘/login’请求的类LoginHandler放在controllers文件夹下，将视图文件login.html放在views文件夹下（需要配置‘template_path’）,而models文件夹下可以存放和数据库处理相关的代码，statics中存放静态文件，如css，js等，需要配置路径：'static_path':'statics'。
#coding:utf-8 import tornado.ioloop
import tornado.web
from controllers.login import LoginHandler class HomeHandler(tornado.web.RequestHandler): #处理'/index'的请求，若是get请求，即调用get方法
def get(self, *args, **kwargs):
self.write('home page') settings = {
'template_path':'views' #配置html文件的目录，即html文件存储在views文件夹路径下
}
app = tornado.web.Application([
(r'/index',HomeHandler), # 路由分发器，HomeHandler为该路由的处理类
(r'/login',LoginHandler),
],**settings) #加入配置文件 if __name__ == '__main__':
app.listen(8080) #监听端口号
tornado.ioloop.IOLoop.instance().start() #开启服务器
app.py
#coding:utf-8
import tornado
class LoginHandler(tornado.web.RequestHandler):
def get(self):
self.render('login.html')
login.py
2.模板
tornado也支持和django类似的模板引擎语言，表达语句用{{ item[0] }}，控制语句{% if %}。。。。 {% end %}，tornado支持if，while，for，try等，但都是以{% end %}结束，不同于django。tornado也支持模板继承，{% extends 'index.html' %} 和 {% block body%}。。。。{% end %}（也是以{% end %}结尾）。
http://www.tornadoweb.org/en/stable/template.html
https://github.com/tornadoweb/tornado/blob/master/tornado/template.py
Tornado默认提供的这些功能其实本质上就是 UIMethod 和 UIModule，我们也可以自定义从而实现类似于Django的simple_tag的功能：
定义：
#coding:utf-8
from tornado import escape def mytag(request,value): #默认会传递一个参数（HomeHandler object），前端需要传值时需要再加一个参数value
#print request
return '<h3>我是tag%s</h3>'%value # 前端默认会对和h3进行转义，需要不转义时前端使用raw 关键字
uimethods.py
#coding:utf-8
from tornado import escape
from tornado.web import UIModule class CustomUIModule(UIModule):
def embedded_javascript(self): # render执行时，会在html文件中加入javascript
return "console.log(123);"
def javascript_files(self): ## render执行时，会在html文件中引入javascript文件
return 'commons.js'
def embedded_css(self):
return '.but{color:red}'
def css_files(self):
return 'commons.css'
def render(self, value):
v = '<h3>我是一个UIModule tag%s</h3>'%value #默认不转义</h3>，前端显示我是一个UIModule tag3
#v = escape.xhtml_escape(v) # 转义</h3>，前端显示<h3>我是一个UIModule tag3</h3>
return v
uimodules.py
设置：
#coding:utf-8 import tornado.ioloop
import tornado.web
from controllers.login import LoginHandler
import uimethods
import uimodules class HomeHandler(tornado.web.RequestHandler): #处理'/index'的请求，若是get请求，即调用get方法
def get(self, *args, **kwargs):
#self.write('home page')
self.render('home.html') settings = {
'template_path':'views', #配置html文件的目录，即html文件存储在views文件夹路径下
'static_path':'statics', # 配置静态url路径，用来存放css，js文件等
'ui_methods':uimethods,
'ui_modules':uimodules,
}
app = tornado.web.Application([
(r'/index',HomeHandler), # 路由分发器，HomeHandler为该路由的处理类
(r'/login',LoginHandler),
],**settings) #加入配置文件 if __name__ == '__main__':
app.listen(8080) #监听端口号
tornado.ioloop.IOLoop.instance().start() #开启服务器
app.py
使用
<!DOCTYPE html>
<html lang="zh-CN">
<head>
<meta charset="UTF-8">
<meta http-equiv="X-UA-Compatible" content="IE=edge">
<meta name="viewport" content="width=device-width, initial-scale=1">
<title>主页</title>
</head>
<body>
{{ mytag(1)}}
{% raw mytag(2) %}
{% module CustomUIModule(3) %}
<p class="but">验证css代码</p>
<p class="but2">验证css文件</p> </body>
</html>
home.html
网页效果：
注意的是在UIModule中可以向html文件中加入css，js代码及文件。
3，静态文件设置
app配置
settings = {
'static_path':'statics', # 配置静态url路径，用来存放css，js文件等
'static_url_prefix':'/statics/', #href中的起始路径
}
html
<link rel="stylesheet" href="/statics/commons.css"> #statics目录下的commons.css
4. 跨站请求伪造（cross site request forgery）
https://www.tornadoweb.org/en/stable/guide/security.html?highlight=ajax
app设置
settings = {
"xsrf_cookies": True,
}
表单使用
<form action="/new_message" method="post">
{% module xsrf_form_html() %}
<input type="text" name="message"/>
<input type="submit" value="Post"/>
</form>
ajax使用:
本质上去cookie中获取_xsrf，再携带_xsrf值提交数据（document.cookie：_xsrf=2|160fb996|ce7f56d73e0cbe6c89a74cb0f92db4b2|1541324310）
function getCookie(name) {
var r = document.cookie.match("\\b" + name + "=([^;]*)\\b");
return r ? r[1] : undefined;
}
jQuery.postJSON = function(url, args, callback) {
args._xsrf = getCookie("_xsrf");
$.ajax({url: url, data: $.param(args), dataType: "text", type: "POST",
success: function(response) {
callback(eval("(" + response + ")"));
}});
};
function getCookie(name) {
var r = document.cookie.match("\\b" + name + "=([^;]*)\\b");
return r ? r[1] : undefined;
}
$('#send').click(function () {
var _xsrf = getCookie('_xsrf')
var msg = $('#msg').val();
$.ajax({
url:'/login',
data:{
'_xsrf':_xsrf,
'msg':msg,
},
type:"POST",
success:function (callback) {
console.log(callback);
}
});
});
5，ajax上传文件
不用ajax前端
<!DOCTYPE html>
<html lang="zh-CN">
<head>
<meta charset="UTF-8">
<meta http-equiv="X-UA-Compatible" content="IE=edge">
<meta name="viewport" content="width=device-width, initial-scale=1">
<title>Title</title>
</head>
<body>
<div>
<input type="file" id="img"/>
<button onclick="upload();">上传</button>
</div> </body>
<script src="/statics/jquery-3.3.1.min.js"></script>
<script>
function upload() {
var file = document.getElementById('img').files[0];
var form = new FormData();
//form.append('k1','v1');
form.append('fileobj',file);
var request = new XMLHttpRequest();
request.open('post','/index',true);
request.send(form);
}
</script>
</html>
ajax前端
<!DOCTYPE html>
<html lang="zh-CN">
<head>
<meta charset="UTF-8">
<meta http-equiv="X-UA-Compatible" content="IE=edge">
<meta name="viewport" content="width=device-width, initial-scale=1">
<title>Title</title>
</head>
<body>
<div>
<input type="file" id="img"/>
<button onclick="upload();">上传</button>
</div> </body>
<script src="/statics/jquery-3.3.1.min.js"></script>
<script>
function upload() {
var file = document.getElementById('img').files[0];
var form = new FormData();
//form.append('k1','v1');
form.append('fileobj',file);
//var request = new XMLHttpRequest();
//request.open('post','/index',true);
//request.send(form);
$.ajax({
url:'/index',
type:'POST',
data:form,
processData:false, //让jquery不处理数据
contentType:false, // 让jquery不设置contentType
success:function (callback) {
console.log(callback);
}
});
} </script>
</html>
后端
#coding:utf-8
import tornado.web
class HomeHandler(tornado.web.RequestHandler):
def get(self):
self.render('LoadFile.html')
def post(self):
fileobjs = self.request.files['fileobj'] #fileobjs为一个列表
for file in fileobjs:
file_name = file['filename'] #fileobjs[0]['filename']
print type(file_name)
with open(file_name,'wb') as f:
f.write(file['body'])
settings={
'template_path':'views',
'static_path':'statics',
'static_url_prefix':'/statics/',
}
application = tornado.web.Application([
(r'/index', HomeHandler)
],**settings)
if __name__ == '__main__':
application.listen(8888)
tornado.ioloop.IOLoop.instance().start()
6，cookie
获取和设置cookie(不加密)：
get_cookie(self, name, default=None): 未取到时返回默认值
def set_cookie(self, name, value, domain=None, expires=None, path="/",expires_days=None, **kwargs):
class HomeHandler(tornado.web.RequestHandler): #处理'/index'的请求，若是get请求，即调用get方法
def get(self, *args, **kwargs):
#self.write('home page')
if self.get_cookie(name='id'):
print self.get_cookie(name='id')
else:
self.set_cookie(name='id',value='asdfg')
self.render('home.html')
获取和设置cookie(加密)：需要在配置中设置秘钥：'cookie_secret'
get_secure_cookie(self, name, value=None, max_age_days=31, min_version=None): 对于加密后的cookie，get_secure_cookie拿到的为解密后的cookie值，get_cookie拿到的为加密的值
set_secure_cookie(self, name, value, expires_days=30, version=None, **kwargs):
class HomeHandler(tornado.web.RequestHandler): #处理'/index'的请求，若是get请求，即调用get方法
def get(self, *args, **kwargs):
if self.get_secure_cookie(name='secret_id'):
print self.get_secure_cookie(name='secret_id') ##前端显示的为加密后，拿到的为明文
else:
self.set_secure_cookie(name='secret_id',value='message') self.render('home.html') settings = {
'template_path':'views', #配置html文件的目录，即html文件存储在views文件夹路径下
'static_path':'statics', # 配置静态url路径，用来存放css，js文件等
'static_url_prefix':'/statics/',
'ui_methods':uimethods,
'ui_modules':uimodules,
'xsrf_cookies':True,
'cookie_secret':'asdfghhj',
}
cookie两个版本的加密算法：
def _create_signature_v1(secret, *parts):
hash = hmac.new(utf8(secret), digestmod=hashlib.sha1)
for part in parts:
hash.update(utf8(part))
return utf8(hash.hexdigest()) def _create_signature_v2(secret, s):
hash = hmac.new(utf8(secret), digestmod=hashlib.sha256)
hash.update(utf8(s))
return utf8(hash.hexdigest())
#加密
def create_signed_value(secret, name, value, version=None, clock=None,
key_version=None):
if version is None:
version = DEFAULT_SIGNED_VALUE_VERSION
if clock is None:
clock = time.time timestamp = utf8(str(int(clock())))
value = base64.b64encode(utf8(value))
if version == 1:
signature = _create_signature_v1(secret, name, value, timestamp)
value = b"|".join([value, timestamp, signature])
return value
elif version == 2:
# The v2 format consists of a version number and a series of
# length-prefixed fields "%d:%s", the last of which is a
# signature, all separated by pipes. All numbers are in
# decimal format with no leading zeros. The signature is an
# HMAC-SHA256 of the whole string up to that point, including
# the final pipe.
#
# The fields are:
# - format version (i.e. 2; no length prefix)
# - key version (integer, default is 0)
# - timestamp (integer seconds since epoch)
# - name (not encoded; assumed to be ~alphanumeric)
# - value (base64-encoded)
# - signature (hex-encoded; no length prefix)
def format_field(s):
return utf8("%d:" % len(s)) + utf8(s)
to_sign = b"|".join([
b"",
format_field(str(key_version or 0)),
format_field(timestamp),
format_field(name),
format_field(value),
b'']) if isinstance(secret, dict):
assert key_version is not None, 'Key version must be set when sign key dict is used'
assert version >= 2, 'Version must be at least 2 for key version support'
secret = secret[key_version] signature = _create_signature_v2(secret, to_sign)
return to_sign + signature
else:
raise ValueError("Unsupported version %d" % version)
#解密：
def _decode_signed_value_v1(secret, name, value, max_age_days, clock):
parts = utf8(value).split(b"|")
if len(parts) != 3:
return None
signature = _create_signature_v1(secret, name, parts[0], parts[1])
if not _time_independent_equals(parts[2], signature):
gen_log.warning("Invalid cookie signature %r", value)
return None
timestamp = int(parts[1])
if timestamp < clock() - max_age_days * 86400:
gen_log.warning("Expired cookie %r", value)
return None
if timestamp > clock() + 31 * 86400:
# _cookie_signature does not hash a delimiter between the
# parts of the cookie, so an attacker could transfer trailing
# digits from the payload to the timestamp without altering the
# signature. For backwards compatibility, sanity-check timestamp
# here instead of modifying _cookie_signature.
gen_log.warning("Cookie timestamp in future; possible tampering %r",
value)
return None
if parts[1].startswith(b""):
gen_log.warning("Tampered cookie %r", value)
return None
try:
return base64.b64decode(parts[0])
except Exception:
return None def _decode_fields_v2(value):
def _consume_field(s):
length, _, rest = s.partition(b':')
n = int(length)
field_value = rest[:n]
# In python 3, indexing bytes returns small integers; we must
# use a slice to get a byte string as in python 2.
if rest[n:n + 1] != b'|':
raise ValueError("malformed v2 signed value field")
rest = rest[n + 1:]
return field_value, rest rest = value[2:] # remove version number
key_version, rest = _consume_field(rest)
timestamp, rest = _consume_field(rest)
name_field, rest = _consume_field(rest)
value_field, passed_sig = _consume_field(rest)
return int(key_version), timestamp, name_field, value_field, passed_sig def _decode_signed_value_v2(secret, name, value, max_age_days, clock):
try:
key_version, timestamp, name_field, value_field, passed_sig = _decode_fields_v2(value)
except ValueError:
return None
signed_string = value[:-len(passed_sig)] if isinstance(secret, dict):
try:
secret = secret[key_version]
except KeyError:
return None expected_sig = _create_signature_v2(secret, signed_string)
if not _time_independent_equals(passed_sig, expected_sig):
return None
if name_field != utf8(name):
return None
timestamp = int(timestamp)
if timestamp < clock() - max_age_days * 86400:
# The signature has expired.
return None
try:
return base64.b64decode(value_field)
except Exception:
return None def get_signature_key_version(value):
value = utf8(value)
version = _get_version(value)
if version < 2:
return None
try:
key_version, _, _, _, _ = _decode_fields_v2(value)
except ValueError:
return None return key_version
加密和解密算法
tornado自带的基于cookie的验证机制：
必须重写方法get_current_user(self):，self.current_user()会调用该方法，拿到当前用户
@tornado.web.authenticated，装饰器修饰的请求会要求验证，self.current_user()中拿到值时，能进行访问，无值时跳转到登录页面（必须进行配置：'login_url':'/login'）
#!/usr/bin/env python
# -*- coding:utf-8 -*- import tornado.ioloop
import tornado.web class BaseHandler(tornado.web.RequestHandler): def get_current_user(self):
return self.get_secure_cookie("login_user") class MainHandler(BaseHandler): @tornado.web.authenticated #需要登录后才能访问（self.current_user()拿到当前用户），否则跳转到登录页面
def get(self):
login_user = self.current_user
self.write(login_user) class LoginHandler(tornado.web.RequestHandler):
def get(self):
self.current_user() self.render('login.html', **{'status': ''}) def post(self, *args, **kwargs): username = self.get_argument('name')
password = self.get_argument('pwd')
if username == 'wupeiqi' and password == '':
self.set_secure_cookie('login_user', 'zack')
self.redirect('/')
else:
self.render('login.html', **{'status': '用户名或密码错误'}) settings = {
'template_path': 'template',
'static_path': 'static',
'static_url_prefix': '/static/',
'cookie_secret': 'aiuasdhflashjdfoiuashdfiuh',
'login_url': '/login'
} application = tornado.web.Application([
(r"/index", MainHandler),
(r"/login", LoginHandler),
], **settings) if __name__ == "__main__":
application.listen(8888)
tornado.ioloop.IOLoop.instance().start()
7, 自定义session框架
预备知识一：字典
任何类实现了__getitem__(), __setitem__(), __delitem__()方法，就能向字典一样存取，删除数据
class Adict(object):
def __init__(self):
self.container = {} def __getitem__(self, key):
print 'get'
if key in self.container:
return self.container[key]
else:
return None
def __setitem__(self, key, value):
print 'set'
self.container[key]=value
def __delitem__(self, key):
print 'del'
del self.container[key] D = Adict() D['user']='zack' #调用 __setitem__方法
D['user'] #调用 __getitem__方法
del D['user'] # 调用 __delitem__方法
预备知识二：类继承
#coding:utf-8
#C实例化时，先调用A的实例化方法，而其会调用self.initialize()时会只执行B的initialize()方法
class A(object):
def __init__(self):
print 'A'
self.initialize() def initialize(self):
print 'A初始化' class B(A): def initialize(self):
print 'B初始化' class C(B):
pass c = C()
单继承
#coding:utf-8
#C实例化时，先调用A的实例化方法，而其会调用self.initialize()时会只调用B的initialize()方法，而B的initialize()方法又调用了A的initialize方法
class A(object):
def __init__(self):
print 'A'
self.initialize() def initialize(self):
print 'A初始化' class B(object): def initialize(self):
print 'B初始化'
super(B,self).initialize() #此处super先寻找其父类，没找到，再找A的initialize方法，（先深度，后广度） class C(B,A):
pass c = C()
多继承
预备知识三：在RequestHandler的源码中，__init__()函数调用了self.initialize()函数
class RequestHandler(object):
"""Base class for HTTP request handlers. Subclasses must define at least one of the methods defined in the
"Entry points" section below.
"""
SUPPORTED_METHODS = ("GET", "HEAD", "POST", "DELETE", "PATCH", "PUT",
"OPTIONS") _template_loaders = {} # type: typing.Dict[str, template.BaseLoader]
_template_loader_lock = threading.Lock()
_remove_control_chars_regex = re.compile(r"[\x00-\x08\x0e-\x1f]") def __init__(self, application, request, **kwargs):
super(RequestHandler, self).__init__() self.application = application
self.request = request
self._headers_written = False
self._finished = False
self._auto_finish = True
self._transforms = None # will be set in _execute
self._prepared_future = None
self._headers = None # type: httputil.HTTPHeaders
self.path_args = None
self.path_kwargs = None
self.ui = ObjectDict((n, self._ui_method(m)) for n, m in
application.ui_methods.items())
# UIModules are available as both `modules` and `_tt_modules` in the
# template namespace. Historically only `modules` was available
# but could be clobbered by user additions to the namespace.
# The template {% module %} directive looks in `_tt_modules` to avoid
# possible conflicts.
self.ui["_tt_modules"] = _UIModuleNamespace(self,
application.ui_modules)
self.ui["modules"] = self.ui["_tt_modules"]
self.clear()
self.request.connection.set_close_callback(self.on_connection_close)
self.initialize(**kwargs) def initialize(self):
"""Hook for subclass initialization. Called for each request. A dictionary passed as the third argument of a url spec will be
supplied as keyword arguments to initialize(). Example:: class ProfileHandler(RequestHandler):
def initialize(self, database):
self.database = database def get(self, username):
... app = Application([
(r'/user/(.*)', ProfileHandler, dict(database=database)),
])
"""
pass
源码
自定义session框架
#coding:utf-8 import tornado.ioloop
import tornado.web
from hashlib import sha1
import time
import os container={}
create_session_id = lambda: sha1('%s%s' % (os.urandom(16), time.time())).hexdigest() class Session(object): #一个类实现了__setitem__，__getitem__就可以向字典一样读取和存取数据 session_id='session_id'
def __init__(self,request):
session_value = request.get_cookie(Session.session_id,None)
if not session_value:
self._id = create_session_id()
else:
if session_value in container:
self._id=session_value
else:
self._id = create_session_id()
request.set_cookie(Session.session_id,self._id)
if self._id not in container:
container[self._id]={} def __setitem__(self, key, value): container[self._id][key]=value print container
def __getitem__(self, key):
if key in container[self._id]:
return container[self._id][key]
else:
return None def __delitem__(self, key):
del container[self._id][key] def clear(self):
del container[self._id] # class BaseHandler(object):
# def initialize(self):
# self.session = Session(self)
# super(BaseHandler,self).initialize() #不会覆盖tornado.web.RequestHandler的initialiaze方法
#
# class HomeHandler(BaseHandler,tornado.web.RequestHandler):
# class BaseHandler(tornado.web.RequestHandler):
def initialize(self): # 覆盖tornado.web.RequestHandler的initialiaze方法，初始化时父类中会调用该方法
self.session = Session(self) class HomeHandler(BaseHandler): def get(self):
user = self.session['user']
if user:
self.write(user)
else:
self.redirect('/login') class LoginHandler(BaseHandler):
def get(self):
self.render('login.html') def post(self):
username = self.get_body_argument('username')
password = self.get_body_argument('password')
if username=='zack' and password=='':
self.session['user']='zack'
self.session['pwd']=''
self.redirect('/index')
else:
self.render('login.html') settings={
'template_path':'views'
}
application = tornado.web.Application([
(r'/index', HomeHandler),
(r'/login', LoginHandler),
],**settings) if __name__ == '__main__':
application.listen(9999)
tornado.ioloop.IOLoop.instance().start()
session框架
8，异步非阻塞
http://www.tornadoweb.org/en/stable/guide/async.html
上面都是利用tornado的同步访问请求，当一个请求被阻塞时，下一个请求访问时不能被处理。如下面代码，当先访问‘/mani’时，由于MainHandler中，get方法sleep会阻塞在此处，此时若访问‘/page’，也会阻塞，等待MainHandler中get方法执行完成后，才会执行PageHandler中的get方法。
#coding:utf-8 import tornado.web
import tornado.ioloop
from tornado.concurrent import Future
import time class MainHandler(tornado.web.RequestHandler): def get(self):
time.sleep(10)
self.write('main') class PageHandler(tornado.web.RequestHandler): def get(self):
self.write('page') application = tornado.web.Application([
(r'/main',MainHandler),
(r'/page',PageHandler)
]) if __name__ == '__main__':
application.listen(8888)
tornado.ioloop.IOLoop.instance().start()
同步阻塞
tornado中，利用装饰器@gen.coroutine +yield Future对象，来支持异步非阻塞。如下面代码，当给MainHandler中get方法加上装饰器@gen.coroutine，并返回Future对象时，就变成了异步非阻塞，也就是说，当我们先访问‘/mani’时，MainHandler中get方法会阻塞在这里，但当我们此时去访问访问‘/page’，PageHandler中的get方法会立即执行，而不会阻塞。
#coding:utf-8 import tornado.web
import tornado.ioloop
from tornado import gen
from tornado.concurrent import Future
import time class MainHandler(tornado.web.RequestHandler): @gen.coroutine
def get(self):
future = Future()
yield future
self.write('main') class PageHandler(tornado.web.RequestHandler): def get(self):
self.write('page') application = tornado.web.Application([
(r'/main',MainHandler),
(r'/page',PageHandler)
]) if __name__ == '__main__':
application.listen(8888)
tornado.ioloop.IOLoop.instance().start()
异步非阻塞
上面写的异步非阻塞并没实际用途，下面是它的一个应用场景，在代码中，MainHandler的get方法中，fetch()比较耗时，但其返回一Future对象，当我们先访问‘/mani’时，MainHandler中get方法会阻塞在这里，但当我们此时去访问访问‘/page’，PageHandler中的get方法会立即执行
#coding:utf-8 import tornado.web
import tornado.ioloop
from tornado import gen, httpclient
from tornado.concurrent import Future class MainHandler(tornado.web.RequestHandler): @gen.coroutine
def get(self):
http = httpclient.AsyncHTTPClient() #发送异步请求
data = yield http.fetch('https://www.youtube.com/',raise_error=False) #其源码中可以看到return future，即返回future对象
print 'done',data
self.write('main')
self.finish('dd') # 加入回调函数处理
# @gen.coroutine
# def get(self):
# http = httpclient.AsyncHTTPClient() #发送异步请求
# yield http.fetch('https://www.youtube.com/',callback=self.done,raise_error=False) #其源码中可以看到return future，即返回future对象
#
# def done(self,response):
# print 'done',response
# self.write('main')
# self.finish('dd') class PageHandler(tornado.web.RequestHandler): def get(self):
self.write('page') application = tornado.web.Application([
(r'/main',MainHandler),
(r'/page',PageHandler)
]) if __name__ == '__main__':
application.listen(8888)
tornado.ioloop.IOLoop.instance().start()
从python 3.5 开始，关键字async 和 await可以用来代替@gen.coroutine +yield，代码如下：
http://www.tornadoweb.org/en/stable/guide/coroutines.html
async def fetch_coroutine(url):
http_client = AsyncHTTPClient()
response = await http_client.fetch(url)
return response.body '''
# Decorated: # Native: # Normal function declaration
# with decorator # "async def" keywords
@gen.coroutine
def a(): async def a():
# "yield" all async funcs # "await" all async funcs
b = yield c() b = await c()
# "return" and "yield"
# cannot be mixed in
# Python 2, so raise a
# special exception. # Return normally
raise gen.Return(b) return b
'''
其实现异步阻塞的关键在于Future对象，下面是其部分源码，可以看到其_result属性初始化没有值，tornado内部会监听每一个Future对象的_result属性值，若没有值时，继续阻塞，若有值时，若某个Future对象的_result属性值有值了，处理该请求，结束阻塞，继续监听其他Future对象。
关于Future类可以参考：https://www.cnblogs.com/silence-cho/p/9867499.html
class Future(object):
"""Represents the result of an asynchronous computation.""" def __init__(self):
"""Initializes the future. Should not be called by clients."""
self._condition = threading.Condition()
self._state = PENDING
self._result = None
self._exception = None
self._traceback = None
self._waiters = []
self._done_callbacks = []
参考文章：
官方文档：http://www.tornadoweb.org/en/stable/index.html
http://www.cnblogs.com/wupeiqi/articles/5341480.html
http://www.cnblogs.com/wupeiqi/articles/5702910.html
http://www.cnblogs.com/wupeiqi/p/6536518.html
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