WSGI 简介及其它

Hoxide

Woodpecker

本幻灯片适合

什么是WSGI

WSGI的目标及特点

目标

特点

WSGI的实现(1)

实现 ( 参看 WSGIImplementations)

WSGI的实现(2)

  • py-lib - 包括了一堆WSGI的实现及工具
  • Python Web
  • WSGIarea
  • Twisted Web2 实验性HTTP服务器 , 有WSGI实现
  • modjy - Jython的WSGI实现
  • isapi_wsgi - IIS的WSGI实现

支持WSGI的Web框架

  • Colubrid 一个轻量级的WSGI工具集(不能说完全是框架), WSGIarea下属
  • CherryPy
  • Django
  • Zope 3
  • QWIP - Quixote 的WSGI接口.

Middleware

WSGI的扩展就在于中间件, 原则上中间件可各种WSGI实现中通用, 下面提供可以找到各种中间件的地方:
  • flup 中间件包括error, gzip, session等
  • WSGIarea
  • 其它各种WSGI实现, 甚至是某些Framework的实现中

WSGI的结构

  • WSGI分为两个方面: Server/Gateway方面和Application/Framework方面
  • WSGI的结构可以形象得表示为如下几种形式:
    WSGI/Server -- Application
    WSGI/Server -- Framework -- Framework Application
    httpd -- WSGI/Gateway -- Application
    httpd -- WSGI/Gateway -- Framework -- Framework Application

一个简单的例子(1)

Application/function

 def simple_app(environ, start_response):
     """Simplest possible application object"""
     status = '200 OK'
     response_headers = [('Content-type','text/plain')]
     start_response(status, response_headers)
     return ['Hello world!\n']

一个简单的例子(2)

Application/class

 class AppClass:
     def __init__(self, environ, start_response):
         self.environ = environ
         self.start = start_response
 
     def __iter__(self):
         status = '200 OK'
         response_headers = [('Content-type','text/plain')]
         self.start(status, response_headers)
         yield "Hello world!\n"

Middleware的例子(1)


 class UpperIter:
     def __init__(self,result,transform_ok):
         if hasattr(result,'close'):
             self.close = result.close
         self._next = iter(result).next
         self.transform_ok = transform_ok
 
     def __iter__(self):
         return self
 
     def next(self):
         if self.transform_ok:
             return self._next().upper()
         else:
             return self._next()

Middleware的例子(2)

 class Upperator:
     transform = False
     def __init__(self, application):
         self.application = application
     def __call__(self, environ, start_response):
         transform_ok = []
 
         def start_upper(status,response_headers,exc_info=None):
 
             # Reset ok flag, in case this is a repeat call
             transform_ok[:]=[]
 
             for name,value in response_headers:
                 if name.lower()=='content-type' and value=='text/plain':
                     transform_ok.append(True)
                     # Strip content-length if present, else it'll be wrong
                     response_headers = [(name,value)
                         for name,value in response_headers
                             if name.lower()<>'content-length'
                     ]
                     break

Middleware的例子(3)

             write = start_response(status,
                                    response_headers,exc_info)
             if exc_info:
                 try:
                     write('Errortype:%s\nValue:%s\nTraceback:%s'%
                           (exc_info[0], exc_info[1],
                            traceback.format_tb(exc_info[2]))
                           )
                 finally:
                     exec_info = None
             if transform_ok:
                 def write_upper(data):
                     write(data.upper())
                 return write_upper
             else:
                 return write
         return UpperIter(self.application(environ,start_upper),
                          transform_ok)

Middleware的例子(4)(错误处理)

 def e_app(environ, start_response):
     try:
         # regular application code here
         status = "200 Froody"
         response_headers = [("content-type","text/plain")]
         start_response(status, response_headers)
         a = 1/0
         return ["normal body goes here"]
     except:
         # XXX should trap runtime issues like MemoryError, KeyboardInterrupt
         #     in a separate handler before this bare 'except:'...
         status = "500 Oops"
         response_headers = [("content-type","text/plain")]
         start_response(status, response_headers, sys.exc_info())
         return ["\nerror body goes here"]

Middleware的例子(5)

 uapp = Upperator(simple_app)
 eapp = Upperator(e_app)

处理环境变量(表单)

 def form_app(environ, start_response):
     status = "200 Froody"
     response_headers = [("content-type","text/html")]
     form = cgi.FieldStorage(fp=environ['wsgi.input'],
                             environ= environ, keep_blank_values=0)
     start_response(status, response_headers)
     if form.has_key('username'):
         name = form['username'].value
     if form.has_key('passwd'):
         passwd = form['passwd'].value        
     return [formstr%(name, passwd)]

pyblosxom

我对WSGI的了解源自pyblosxom, 他是个标准的WSGI应用, 通过middleware扩展获得session后, 我写了一些插件, 可见mdxx的代码库.

本幻灯片使用软件

  • S5 Woodpecker 模板
  • python2html.1.py
  • Apache + mod_python + mp_wsgi_handler/wsgiref

    • 谢谢!