A server model with middleware support by using closure

middleware_closure_implement.py

# 上下文类，本例中主要用于存储当前调用的下文，即内层中间件
class Context():
    def __init__(self):
        self._next = []

    @property
    def next(self):
        return self._next


class Server():
    def __init__(self):
        self._middlewares = []   # 所有添加中间件
        self._funcs = {}    # 所有添加的核心件

    def add_middleware(self, middleware_func):
        self._middlewares.append(middleware_func)
        return middleware_func

    def add_func(self, name):
        def decorate(func):
            self._funcs.setdefault(name, func)
            return func
        return decorate

    def _load_middleware(self, ctx, func):
        def next(*args, **kwargs):
            return func(ctx, *args, **kwargs)
        for middleware in reversed(self._middlewares):
            # 使用闭包来封装中间件
            def f(middleware=middleware, next=next):
                def new_next(*args, **kwargs):
                    ctx._next = next
                    return middleware(ctx, *args, **kwargs)
                new_next.__name__ = getattr(middleware, '__name__')
                return new_next
            next = f()
        return next

    def _wrap(self, func):
        def f(*args, **kwargs):
            ctx = Context()
            return self._load_middleware(ctx, func)(*args, **kwargs)
        return f

    def initilize(self):
        for name, func in self._funcs.items():
            self.__setattr__(name, self._wrap(func))


server = Server()


@server.add_middleware
def the_first_middleware(ctx, *args, **kwargs):
    print("The first one")
    return ctx.next(*args, **kwargs)


@server.add_middleware
def the_second_middleware(ctx, *args, **kwargs):
    print("The second one")
    return ctx.next(*args, **kwargs)


@server.add_middleware
def the_last_middleware(ctx, *args, **kwargs):
    print("The last one")
    return ctx.next(*args, **kwargs)


@server.add_func('core_func')
def core_func(ctx, *args, **kwargs):
    return "The Core Function"


server.initilize()
print(server.core_func())