python web 开发之Flask中间件与请求处理钩子的最佳实践

@app.before_request
def require_login():
    # 检查所有请求是否需要登录
    if request.endpoint not in ['login', 'static']:
        if 'user_id' not in session:
            return redirect(url_for('login'))
@app.before_request
def connect_db():
    # 为每个请求建立数据库连接
    g.db = get_db_connection()

@app.after_request
def add_cors_headers(response):
    # 添加CORS头
    response.headers['Access-Control-Allow-Origin'] = '*'
    response.headers['Access-Control-Allow-Methods'] = 'GET, POST, PUT, DELETE'
    return response
@app.after_request
def log_response(response):
    # 记录响应信息
    app.logger.info(f"Response: {response.status_code}")
    return response

@app.teardown_request
def close_db_connection(exception=None):
    # 确保关闭数据库连接
    db = g.pop('db', None)
    if db is not None:
        db.close()
    if exception:
        app.logger.error(f"Request teardown with exception: {exception}")

# 替代方案：使用app.cli.command或手动调用
with app.app_context():
    initialize_app()

from flask import g
@app.before_request
def load_user():
    # 在请求期间存储用户信息
    if 'user_id' in session:
        g.user = User.query.get(session['user_id'])
@app.route('/profile')
def profile():
    # 在视图函数中使用g对象
    if not hasattr(g, 'user'):
        abort(401)
    return render_template('profile.html', user=g.user)

@app.before_request
def before_request():
    g.db = db.session
@app.teardown_request
def teardown_request(exception):
    db = g.pop('db', None)
    if db is not None:
        if exception is None:
            db.commit()
        else:
            db.rollback()
        db.close()

class ReverseProxyMiddleware:
    def __init__(self, app):
        self.app = app
    def __call__(self, environ, start_response):
        # 处理X-Forwarded-For头
        if 'HTTP_X_FORWARDED_FOR' in environ:
            environ['REMOTE_ADDR'] = environ['HTTP_X_FORWARDED_FOR'].split(',')[0]
        return self.app(environ, start_response)
app.wsgi_app = ReverseProxyMiddleware(app.wsgi_app)

def json_only(f):
    @wraps(f)
    def wrapper(*args, **kwargs):
        if not request.is_json:
            return jsonify({"error": "Content-Type must be application/json"}), 400
        return f(*args, **kwargs)
    return wrapper
@app.route('/api', methods=['POST'])
@json_only
def api_endpoint():
    data = request.get_json()
    return jsonify({"status": "success"})

@app.before_request
def start_timer():
    g.start_time = time.time()
@app.after_request
def log_request_time(response):
    if hasattr(g, 'start_time'):
        duration = (time.time() - g.start_time) * 1000  # 毫秒
        app.logger.info(f"Request took {duration:.2f}ms")
    return response

@app.teardown_request
def handle_errors(exception):
    if exception:
        if isinstance(exception, SQLAlchemyError):
            db.session.rollback()
            app.logger.error(f"Database error: {exception}")
            return jsonify({"error": "Database operation failed"}), 500

@app.before_request
def detect_device():
    user_agent = request.user_agent.string.lower()
    g.is_mobile = 'mobile' in user_agent or 'android' in user_agent or 'iphone' in user_agent

@app.before_request
def hook1():
    print("Hook 1 executed")
@app.before_request
def hook2():
    print("Hook 2 executed")
@app.after_request
def hook3(response):
    print("Hook 3 executed")
    return response
@app.after_request
def hook4(response):
    print("Hook 4 executed")
    return response

def register_hooks_for_env(env):
    if env == 'production':
        @app.before_request
        def production_only():
            # 生产环境特定逻辑
            pass

@app.before_request
def csrf_protect():
    if request.method == "POST":
        token = session.pop('_csrf_token', None)
        if not token or token != request.form.get('_csrf_token'):
            abort(403)
def generate_csrf_token():
    if '_csrf_token' not in session:
        session['_csrf_token'] = os.urandom(24).hex()
    return session['_csrf_token']
app.jinja_env.globals['csrf_token'] = generate_csrf_token

@app.before_request
def check_request_content():
    if request.content_length and request.content_length > 1024 * 1024:  # 1MB限制
        abort(413)  # Payload Too Large

@app.teardown_request
def cleanup_g(exception=None):
    # 显式清理g对象
    for key in list(g.keys()):
        g.pop(key)