python aiohttp.web 中间件如何工作

Question

根据文档

The handler passed in to a middleware factory is the handler returned by the next middleware factory. The last middleware factory always receives the request handler selected by the router itself (by UrlDispatcher.resolve()).

我认为 UrlDispatcher.resolve() 将 return 我分配的注册处理程序，所以我编写了这段代码。根据我的理解，当访问页面 127.0.0.1:9000 时，索引处理程序将用作 m1

的处理程序

import logging;
import asyncio
from aiohttp import web

logging.basicConfig(level=logging.INFO)

@asyncio.coroutine
def m1(app,handler):
    def log(request):
        r = yield from handler(request)
        logging.info(str(r))

@asyncio.coroutine
def index(request):
    return web.Response(body=b'<h1>Aswesome</h1>')

@asyncio.coroutine
def names(request):
    return web.Response(text='<h1>%s</h1>' % request.match_info['name'])

@asyncio.coroutine
def init(loop):
    app = web.Application(loop=loop, middlewares=[
        m1
    ])
    app.router.add_route('GET','/',index)
    app.router.add_route('GET','/{name:\w+}',names)
    srv = yield from loop.create_server(app.make_handler(),'127.0.0.1',9000)
    logging.info('server started at http://127.0.0.1:9000')
    return srv

loop = asyncio.get_event_loop()
loop.run_until_complete(init(loop))
loop.run_forever()

当我运行代码并访问 127.0.0.1:9000 的服务器时，我得到了

  File "/home/os/Documents/Python/web/lib/python3.5/site-packages/aiohttp/web.py", line 90, in handle_request
    resp = yield from handler(request)
TypeError: 'NoneType' object is not callable

在我看来，NoneType 作为处理程序传递到 m1 中间件

Answer 1

您的中间件 returns 什么都没有，但应该返回中间件处理程序 log。我在您的代码中添加了一行 returns log.

@asyncio.coroutine
def m1(app,handler):
    def log(request):
        r = yield from handler(request)
        logging.info(str(r))
    return log  # changed

有关详细信息，请参阅 documentation regarding middlewares。此外，值得研究一下 Python 3.5，它提供了 async/await 语法来处理可等待对象，也就是协程。 aiohttp.

的贡献者建议使用语法

参见官方 PEP-492 or slides 来自 Igor Davydenko 的关于新语法介绍的演讲。

python aiohttp.web 中间件如何工作

how does python aiohttp.web middleware work

python

aiohttp