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Python WSGI框架开发完全指南 - 从零实现自定义Web框架

HeJuan
Python
2025-07-19
198

Python WSGI框架开发完全指南

从零开始构建你自己的Python Web框架

什么是WSGI？

WSGI（Web Server Gateway Interface）是Python Web开发的核心标准，它定义了Web服务器与Python应用程序之间的通用接口。通过遵循WSGI规范，开发者可以创建与多种Web服务器兼容的Web应用，而不必关心底层服务器的实现细节。

WSGI规范的核心要素

一个WSGI应用程序需要满足以下要求：

必须是一个可调用对象（函数、类或实现了__call__方法的实例）
接受两个参数：环境变量字典（environ）和回调函数（start_response）
调用start_response函数设置HTTP状态和响应头
返回一个可迭代对象作为响应体

实现WSGI框架的步骤

1. 创建基础框架类

class PyFrame:
    def __init__(self):
        self.routes = {}
        self.middleware = []
    
    def __call__(self, environ, start_response):
        return self.handle_request(environ, start_response)
    
    def handle_request(self, environ, start_response):
        # 请求处理逻辑将在这里实现
        pass
    
    def route(self, path):
        def decorator(handler):
            self.routes[path] = handler
            return handler
        return decorator
    
    def add_middleware(self, middleware):
        self.middleware.insert(0, middleware)

2. 实现请求路由

def handle_request(self, environ, start_response):
    request = Request(environ)
    path = request.path
    
    # 查找匹配的路由
    handler = self.routes.get(path)
    if not handler:
        # 尝试匹配动态路由
        handler, args = self.match_dynamic_route(path)
        if not handler:
            return self.not_found(start_response)
    
    # 应用中间件
    response = self.apply_middleware(request, handler, args)
    
    # 执行处理函数并返回响应
    return response(environ, start_response)

def match_dynamic_route(self, path):
    for route_path, handler in self.routes.items():
        if '{' in route_path:
            # 实现简单的动态路由匹配逻辑
            route_parts = route_path.split('/')
            path_parts = path.split('/')
            
            if len(route_parts) != len(path_parts):
                continue
                
            args = {}
            match = True
            for i in range(len(route_parts)):
                if route_parts[i].startswith('{') and route_parts[i].endswith('}'):
                    arg_name = route_parts[i][1:-1]
                    args[arg_name] = path_parts[i]
                elif route_parts[i] != path_parts[i]:
                    match = False
                    break
            
            if match:
                return handler, args
    return None, None

3. 实现请求和响应对象

class Request:
    def __init__(self, environ):
        self.environ = environ
        self.method = environ.get('REQUEST_METHOD', 'GET')
        self.path = environ.get('PATH_INFO', '/')
        self.query = environ.get('QUERY_STRING', '')
        self.headers = self.parse_headers(environ)
    
    def parse_headers(self, environ):
        headers = {}
        for key, value in environ.items():
            if key.startswith('HTTP_'):
                header_name = key[5:].replace('_', '-').title()
                headers[header_name] = value
        return headers

class Response:
    def __init__(self, body, status='200 OK', headers=None):
        self.body = body
        self.status = status
        self.headers = headers or [('Content-Type', 'text/html')]
    
    def __call__(self, environ, start_response):
        start_response(self.status, self.headers)
        if isinstance(self.body, str):
            return [self.body.encode('utf-8')]
        return [self.body]

4. 添加中间件支持

def apply_middleware(self, request, handler, args):
    def middleware_chain(request, handler, args):
        # 最后一个中间件调用实际的处理函数
        return handler(request, **args)
    
    # 反向应用中间件（最先添加的中间件最后执行）
    for mw in self.middleware:
        current_chain = middleware_chain
        middleware_chain = lambda r, h, a: mw(r, lambda r: current_chain(r, h, a))
    
    return middleware_chain(request, handler, args)

# 示例中间件：记录请求日志
def log_middleware(request, next_handler):
    print(f"Request: {request.method} {request.path}")
    response = next_handler(request)
    print(f"Response: {response.status}")
    return response

完整框架示例

from wsgiref.simple_server import make_server

# 初始化框架
app = PyFrame()
app.add_middleware(log_middleware)

# 添加路由
@app.route('/')
def home(request):
    return Response("<h1>欢迎使用PyFrame!</h1>")

@app.route('/user/{username}')
def user_profile(request, username):
    return Response(f"<h1>用户主页: {username}</h1>")

# 启动服务器
if __name__ == '__main__':
    server = make_server('localhost', 8000, app)
    print("服务器运行在 http://localhost:8000")
    server.serve_forever()