Flask middleware for specific route

Question

I made API Server with Python Flask-RESTful.

My system use token authentication for verify permission.

So, I added middleware for verify token.

For example, code like this,

[middleware.py]

class Test(object):
    def __init__(self, app):
        self.app = app

    def __call__(self, environ, start_response):
        print("gogo")
        return self.app(environ, start_response)

[app.py]

from flask import Flask
from flask_restful import Api
from api.board import Article
from api.auth import Login, Register, RefreshToken
from middleware import Test


app = Flask(__name__)
api = Api(app)

api.add_resource(Login, '/login')
api.add_resource(Register, '/register')
api.add_resource(RefreshToken, '/refresh')

# middleware here
app.wsgi_app = Test(app.wsgi_app)
api.add_resource(Article, '/article')

if __name__ == '__main__':
    app.run(debug=True)

I insert app.wsgi_app = Test(app.wsgi_app) before /article.

So I expect that only access to /article will print "gogo", however every route print "gogo".

Maybe every route pass through with middleware.

How can I apply middleware for specific route? (In this code, only /article)

Answer 1

There are a few ways how to add custom processing before specific endpoint.

1) Using python decorator:

from functools import wraps

def home_decorator():
    def _home_decorator(f):
        @wraps(f)
        def __home_decorator(*args, **kwargs):
            # just do here everything what you need
            print('before home')
            result = f(*args, **kwargs)
            print('home result: %s' % result)
            print('after home')
            return result
        return __home_decorator
    return _home_decorator


@app.route('/home')
@home_decorator()
def home():
    return 'Hello'

2) Using before_request

@app.before_request
def hook():
    # request - flask.request
    print('endpoint: %s, url: %s, path: %s' % (
        request.endpoint,
        request.url,
        request.path))
    # just do here everything what you need...

3) Using middleware. Just add condition on request path.

class Middleware:

    def __init__(self, app):
        self.app = app

    def __call__(self, environ, start_response):
        # not Flask request - from werkzeug.wrappers import Request
        request = Request(environ)
        print('path: %s, url: %s' % (request.path, request.url))
        # just do here everything what you need
        return self.app(environ, start_response)


@app.route('/home')
def home():
    return 'Hello'


app.wsgi_app = Middleware(app.wsgi_app)

4) Also you can use before_request_funcs to set list of functions before specific blueprint.

api = Blueprint('my_blueprint', __name__)


def before_my_blueprint():
    print(111)


@api.route('/test')
def test():
    return 'hi'


app.before_request_funcs = {
    # blueprint name: [list_of_functions]
    'my_blueprint': [before_my_blueprint]
}

app.register_blueprint(api)

Hope this helps.