如何使用werkzeug创建WSGI APP

注意 ：

1、定义__call__的意义

class App():
def __init__(self):
pass
def method(self):
pass

app=App()

app() #错误，因为app，即对象的实例,没有括号运算符

class App2():
def __init__(self):
pass
def method(self):
pass
def __call__(self):
print 'call'

app2=App2()
app2() #print call     回去调用__call__里面的内容

2、WSGI的Request和Response讲解:

3、自定义wsgi 程序

class Shortly(object):
def __init__(self, config):
self.redis = redis.Redis(config[‘redis_host’], config[‘redis_port’])

def dispatch_request(self, request):
return Response(‘Hello World!’)

def wsgi_app(self, environ, start_response):
request = Request(environ)
response = self.dispatch_request(request)
return response(environ, start_response)

def __call__(self, environ, start_response):
return self.wsgi_app(environ, start_response)

def create_app(redis_host=‘localhost’, redis_port=6379, with_static=True):
app = Shortly({
‘redis_host’: redis_host,
‘redis_port’: redis_port
})
if with_static:
app.wsgi_app = SharedDataMiddleware(app.wsgi_app, {
‘/static’: os.path.join(os.path.dirname(__file__), ‘static’)
})
return app

完成基本框架

4、 继续完善

在__init__ 里面 渲染模板并连接到redis 

def __init__(self, config):
self.redis = redis.Redis(config[‘redis_host’], config[‘redis_port’])
template_path = os.path.join(os.path.dirname(__file__), ‘templates’)
self.jinja_env = Environment(loader=FileSystemLoader(template_path),
autoescape=True)

## 创建一个Map实例，并增加一些Rule对象。每个规则包含一个用来尝试针对一个endpoint匹配URL的模式模板。endpoint通常是一个字符串，可以用来唯一识别这个URL

## 另一个带有同样的规则，只是在短链接之后增加了一个加号（+），将其连接到短链接的细节信息。

self.url_map = Map([
Rule(‘/’, endpoint=‘new_url’),
Rule(‘/<short_id>’, endpoint=‘follow_short_link’),
Rule(‘/<short_id>+’, endpoint=’short_link_details’)
])

def render_template(self, template_name, **context):
t = self.jinja_env.get_template(template_name)
return Response(t.render(context), mimetype=’text/html’)

## 添加视图 view

def on_new_url(self, request): 
error = None 
url = ‘’ 
if request.method = ‘POST’: 
url = request.form[‘url’] 
if not is_valid_url(url): 
error = ‘Please enter a valid URL’ 
else: 
short_id = self.insert_url(url) 
return redirect(‘/%s+’ % short_id) 
return self.render_template(‘new_url.html’, error=error, url=url)

完整代码下载：

# -*- coding: utf-8 -*-
"""
    shortly
    ~~~~~~~
    A simple URL shortener using Werkzeug and redis.
    :copyright: (c) 2014 by the Werkzeug Team, see AUTHORS for more details.
    :license: BSD, see LICENSE for more details.
"""
import os
import redis
import urlparse
from werkzeug.wrappers import Request, Response
from werkzeug.routing import Map, Rule
from werkzeug.exceptions import HTTPException, NotFound
from werkzeug.wsgi import SharedDataMiddleware
from werkzeug.utils import redirect

from jinja2 import Environment, FileSystemLoader


def base36_encode(number):
    assert number >= 0, 'positive integer required'
    if number == 0:
        return '0'
    base36 = []
    while number != 0:
        number, i = divmod(number, 36)
        base36.append('0123456789abcdefghijklmnopqrstuvwxyz'[i])
    return ''.join(reversed(base36))


def is_valid_url(url):
    parts = urlparse.urlparse(url)
    return parts.scheme in ('http', 'https')


def get_hostname(url):
    return urlparse.urlparse(url).netloc


class Shortly(object):

    def __init__(self, config):
        self.redis = redis.Redis(config['redis_host'], config['redis_port'])
        template_path = os.path.join(os.path.dirname(__file__), 'templates')
        self.jinja_env = Environment(loader=FileSystemLoader(template_path),
                                     autoescape=True)
        self.jinja_env.filters['hostname'] = get_hostname

        self.url_map = Map([
            Rule('/', endpoint='new_url'),
            Rule('/<short_id>', endpoint='follow_short_link'),
            Rule('/<short_id>+', endpoint='short_link_details')
        ])

    def on_new_url(self, request):
        error = None
        url = ''
        if request.method == 'POST':
            url = request.form['url']
            if not is_valid_url(url):
                error = 'Please enter a valid URL'
            else:
                short_id = self.insert_url(url)
                return redirect('/%s+' % short_id)
        return self.render_template('new_url.html', error=error, url=url)

    def on_follow_short_link(self, request, short_id):
        link_target = self.redis.get('url-target:' + short_id)
        if link_target is None:
            raise NotFound()
        self.redis.incr('click-count:' + short_id)
        return redirect(link_target)

    def on_short_link_details(self, request, short_id):
        link_target = self.redis.get('url-target:' + short_id)
        if link_target is None:
            raise NotFound()
        click_count = int(self.redis.get('click-count:' + short_id) or 0)
        return self.render_template('short_link_details.html',
            link_target=link_target,
            short_id=short_id,
            click_count=click_count
        )

    def error_404(self):
        response = self.render_template('404.html')
        response.status_code = 404
        return response

    def insert_url(self, url):
        short_id = self.redis.get('reverse-url:' + url)
        if short_id is not None:
            return short_id
        url_num = self.redis.incr('last-url-id')
        short_id = base36_encode(url_num)
        self.redis.set('url-target:' + short_id, url)
        self.redis.set('reverse-url:' + url, short_id)
        return short_id

    def render_template(self, template_name, **context):
        t = self.jinja_env.get_template(template_name)
        return Response(t.render(context), mimetype='text/html')

    def dispatch_request(self, request):
        adapter = self.url_map.bind_to_environ(request.environ)
        try:
            endpoint, values = adapter.match()
            return getattr(self, 'on_' + endpoint)(request, **values)
        except NotFound, e:
            return self.error_404()
        except HTTPException, e:
            return e

    def wsgi_app(self, environ, start_response):
        request = Request(environ)
        response = self.dispatch_request(request)
        return response(environ, start_response)

    def __call__(self, environ, start_response):
        return self.wsgi_app(environ, start_response)


def create_app(redis_host='localhost', redis_port=6379, with_static=True):
    app = Shortly({
        'redis_host':       redis_host,
        'redis_port':       redis_port
    })
    if with_static:
        app.wsgi_app = SharedDataMiddleware(app.wsgi_app, {
            '/static':  os.path.join(os.path.dirname(__file__), 'static')
        })
    return app


if __name__ == '__main__':
    from werkzeug.serving import run_simple
    app = create_app()
    run_simple('127.0.0.1', 5000, app, use_debugger=True, use_reloader=True)

https://github.com/pallets/werkzeug/tree/master/examples/shortly     含html页面下载