54web开发6_拦截器_上下文支持

 

 

目录

interceptor，拦截器：... 1

分类：... 1

加入拦截器功能的方式：... 2

拦截器fn函数的设计：... 2

上下文支持：... 2

完整代码：... 4

 

 

interceptor，拦截器：

在请求处理环节的某处加入处理，有可能是中断后续的处理；

类似java的structs框架中的拦截器，servelet中也有拦截器；

 

分类：

根据拦截点不同，分：请求挂载；响应拦截；

根据影响面，分：全局拦截（在Application中拦截）；局部拦截（在Router中拦截）；

 

不能在handler中作拦截，即不能在一个完整的功能模块中拦截；

在__call__()进去之后，__call__()return之前作拦截；

 

注：

依次执行，一环扣一环，上一步的输出是下一步的输入；

拦截器可以是多个，多个拦截器是有顺序的；

数据response之前执行的命名为pre_interceptor，之后的执行命名为post_interceptor；

某些特定功能要求最终返回给用户为404，经fn后rerturn None，这样达到目的就行；

 

 

加入拦截器功能的方式：

方式1：

Application和Router类中直接加入；

把拦截器的相关方法，属性分别添加到相关类中；

Router的拦截器是每个实例都不一样，适合用此种；

方式2：

Mixin；

Application和Router都需要这个拦截器功能，这两个类有无关系，可用mixin方式，将属性方法组合进来；

Application适合使用此种；

 

 

拦截器fn函数的设计：

def fn(app,request:Request)->Request: pass   #fn不能影响数据继续向下一级的传递，即是透明的，如handle的输入要是request，前面的拦截的输出也要是request，handle处理后是response，经拦截器最终到__call__()也要是response

def fn(app,reqeust:Request)->Request: pass   #引入app即Application的实例，是为以后从Application上获取一些全局信息

 

 

 

上下文支持：

为把一些应用数据、配置数据、数据库连接等全局共享数据提供给所有对象使用，增加一个字典，存储这些共享数据；

为方便访问，提供字典的属性化访问的类，且该字典可写；

 

例：

class Context(dict):

    def __getattr__(self, item):

        try:

            return self[item]

        except KeyError:

            raise AttributeError('Attribute {} Not Found'.fomrat(item))

       

    def __setattr__(self, key, value):

        self[key] = value

 

class Application:

    ctx = Context()

    ROUTERS = []

 

    def __init__(self, **kwargs):

        self.ctx.app = self

        for k, v in kwargs:

            self.ctx[k] = v

 

 

Router的每一个实例中增加上下文属性，实例自己使用；

Router实例如何使用全局上下文？

用新的处理方法，增加NestedContext类，每一个Router实例的上下文字典内部关联一个全局字典的引用，如果自己的字典中找不到，就去全局里找；

Router实例什么时候关联全局字典？

在路由注册时较合适，只需修改下注册函数即可

 

例，错误示例：

class Mixin:

         # def __init__(self): pass   #仅实现功能，不能有初始化

 

class A:

         def __init__(self): pass

 

class C(Mixin, A):

         def __init__(self):

                   super().__init__()   #错误，这样用的是Mixin的初始化方法，把A的覆盖掉了

 

 

例：

class Context(dict):

    def __getattr__(self, item):

        try:

            return self[item]

        except KeyError:

            raise AttributeError('Attribute {} Not Found'.format(item))

 

    def __setattr__(self, key, value):

        self[key] = value

 

 

class NestedContext(Context):

    def __init__(self, globalcontext:Context=None):

        super().__init__()   #此句可没有，父类中未初始化，按标准流程应写上

        self.relate(globalcontext)

 

    def relate(self, globalcontext:Context=None):

        self.globalcontext = globalcontext

 

    def __getattr__(self, item):

        if item in self.keys():

            return self[item]

        return self.globalcontext[item]

 

ctx = Context()

ctx.x = 6

ctx.y = 'a'

 

nc = NestedContext()

nc.relate(ctx)

nc.x = 8

 

print(nc)   #

print(nc.x)   #自己的

print(nc.y)   #全局的

print(nc.z)   #KeyError

输出：

{'globalcontext': {'y': 'a', 'x': 6}, 'x': 8}

8

a

Traceback (most recent call last):

  File "E:/git_practice/cmdb/example_wsgi_interceptor.py", line 37, in <module>

    print(nc.z)

  File "E:/git_practice/cmdb/example_wsgi_interceptor.py", line 24, in __getattr__

    return self.globalcontext[item]

KeyError: 'z'

 

 

 

完整代码：

将如下代码改为单例（单例模式，只允许创建一个实例）；

多线程时，要么锁要么信号量；

多进程时，用进程中的信号量；

 

例：

from wsgiref.simple_server import make_server

from webob import Request, Response, dec, exc

import re

 

 

class DictObj:

    def __init__(self, d: dict):

        if not isinstance(d, dict):

            self.__dict__['_dict'] = {}

        else:

            self.__dict__['_dict'] = d

 

    def __getattr__(self, item):

        try:

            return self._dict[item]

        except KeyError:

            raise AttributeError('Attribute {} Not Found '.format(self._dict))

 

    def __setattr__(self, key, value):

        raise NotImplementedError

 

 

class Context(dict):

    def __getattr__(self, item):

        try:

            return self[item]

        except KeyError:

            raise AttributeError('Attrubute {} Not found'.format(item))

 

    def __setattr__(self, key, value):

        self[key] = value

 

 

class NestedContext(Context):

    def __init__(self, globalcontext:Context=None):

        super().__init__()

        self.relate(globalcontext)

 

    def relate(self, globalcontext:Context=None):

        self.globalcontext = globalcontext

 

    def __getattr__(self, item):

        if item in self.keys():

            return self[item]

        return self.globalcontext[item]

 

 

class Router:

    pattern = '/({[^{}:]+:?[^{}:]*})'  # /{name:str}

    regex = re.compile(pattern)

 

    TYPEPATTERNS = {

        'str': r'[^/]+',

        'word': r'\w+',

        'int': r'[+-]?\d+',

        'float': r'[+-]\d+.\d+',

        'any': r'.+'

    }

 

    TYPECAST = {

        'str': str,

        'word': str,

        'int': int,

        'float': float,

        'any': str

    }

 

    def _transform(self, kv: str):

        name, _, type = kv.strip('/{}').partition(':')

        return '/(?P<{}>{})'.format(name, self.TYPEPATTERNS.get(type, '\w+')), name, self.TYPECAST.get(type, str)

 

    def _parse(self, src: str):

        start = 0

        res = ''

        translator = {}

        while True:

            matcher = self.regex.search(src, start)

            if matcher:

                res += matcher.string[start: matcher.start()]

                tmp = self._transform(matcher.string[matcher.start():matcher.end()])

                res += tmp[0]

                translator[tmp[1]] = tmp[2]

                start = matcher.end()

            else:

                break

        if res:

            return res, translator

        else:

            return src, translator

 

    def __init__(self, prefix: str=''):

        self.__prefix = prefix.rstrip('/\\')

        self.__routertable = []   #[(methods, regex, translator, handler)]

 

        self.pre_interceptor = []

        self.post_interceptor = []

 

        self.ctx = NestedContext()

 

    @property

    def prefix(self):

        return self.__prefix

 

    def register_preinterceptor(self, fn):

        self.pre_interceptor.append(fn)

        return fn

 

    def register_postinterceptor(self, fn):

        self.post_interceptor.append(fn)

        return fn

 

    def route(self, rule, *methods):

        def wrapper(handler):

            pattern, translator = self._parse(rule)

            self.__routertable.append((methods, re.compile(pattern), translator, handler))

            return handler

        return wrapper

 

    def get(self, pattern):

        return self.route(pattern, 'GET')

 

    def post(self, pattern):

        return self.route(pattern, 'POST')

 

    def head(self, pattern):

        return self.route(pattern, 'HEAD')

 

    def match(self, request: Request)->Response:

        print(request.path)

        if not request.path.startswith(self.prefix):

            return

 

        for fn in self.pre_interceptor:

            request = fn(self.ctx, request)

 

        for methods, regex, translator, handler in self.__routertable:

            print(methods, regex, translator, handler)

            if not methods or request.method.upper() in methods:

                matcher = regex.search(request.path.replace(self.prefix, '', 1))

                if matcher:

                    print(matcher)

                    newdict = {}

                    for k, v in matcher.groupdict().items():

                        newdict[k] = translator[k](v)

                    print(newdict)

                    request.vars = DictObj(newdict)

                    return handler(request)

        # return

 

 

class Application:

    ctx = Context()

    ROUTERS = []

 

    def __init__(self, **kwargs):

        self.ctx.app = self

        for k, v in kwargs:

            self.ctx[k] = v

 

    PRE_INTERCEPTOR = []

    POST_INTERCEPTOR = []

 

    @classmethod

    def register_preinterceptor(cls, fn):

        cls.PRE_INTERCEPTOR.append(fn)

        return fn

 

    @classmethod

    def register_postinterceptor(cls, fn):

        cls.POST_INTERCEPTOR.append(fn)

        return fn

 

    @classmethod

    def register(cls, router: Router):

        router.ctx.relate(cls.ctx)

        router.ctx.router = router

        cls.ROUTERS.append(router)

 

    @dec.wsgify

    def __call__(self, request: Request) -> Response:

        for fn in self.PRE_INTERCEPTOR:

            request = fn(self.ctx, request)

 

        for router in self.ROUTERS:

            response = router.match(request)

 

            for fn in self.POST_INTERCEPTOR:

                response = fn(self.ctx, request, response)

 

            if response:

                return response

        raise exc.HTTPNotFound('<h1>the page not found</h1>')

 

idx = Router()

py = Router('/python')

 

Application.register(idx)

Application.register(py)

 

# @py.get('/{name:str}')

# @py.get('/{id:int}')

@py.get('/{name:str}/{id:int}')

def showpython(request):

    res = Response()

    # print(request.__dict__)

    # res.body = '<h1>hello python; vars = {}</h1>'.format(request.vars.name).encode()

    res.body = '<h1>hello python; vars = {}</h1>'.format(request.vars.id).encode()

    return res

 

@idx.route('^/$')

def index(request):

    res = Response()

    res.body = '<h1>welcome</h1>'.encode()

    return res

 

@Application.register_preinterceptor

def showheaders(ctx: Context, request: Request) -> Response:

    print(request.path)

    print(request.user_agent)

    return request

 

@py.register_preinterceptor

def showprefix(ctx: Context, request: Request)->Response:

    print('~~~~~~~prefix = {}'.format(ctx.router.prefix))

    return request

 

 

if __name__ == '__main__':

    ip = '127.0.0.1'

    port = 9999

    server = make_server(ip, port, Application())

    try:

        server.serve_forever()

    except Exception as e:

        print(e)

    finally:

        server.shutdown()

        server.server_close()

 

 

 

 

 

转载于:https://blog.51cto.com/jowin/2394498