flask之before_request和after_request

1 before_request

类比django中间件中的process_request，在请求收到之前绑定一个函数做一些事情

# -*- coding: utf-8 -*-
# @Time    : 2021/12/13 20:30
# @Author  : dzg

from flask import Flask

app = Flask(__name__)


@app.before_request
def before_request():
    print('来了')


@app.route('/')
def index():
    print('index')
    return 'ok'


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

基于可以做用户登录认证

before_request没有参数

2 after_request

类比django中间件中的process_response，每一个请求之后绑定一个函数，如果请求没有异常

# -*- coding: utf-8 -*-
# @Time    : 2021/12/13 20:30
# @Author  : dzg

from flask import Flask

app = Flask(__name__)


@app.after_request
def after_request(response):
    print(response)
    print(type(response))

    print('走了')

    return response


@app.route('/')
def index():
    print('index')
    return 'ok'


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

after_request有参数response，并且要返回response，不然会报错

3 执行顺序

• before_request从上到下
• after_request从下到上

# -*- coding: utf-8 -*-
# @Time    : 2021/12/13 20:30
# @Author  : dzg

from flask import Flask

app = Flask(__name__)


@app.before_request
def before_request1():
    print('before_request1')


@app.before_request
def before_request2():
    print('before_request2')


@app.after_request
def after_request1(response):
    print('after_request1')

    return response


@app.after_request
def after_request2(response):
    print('after_request2')

    return response


@app.route('/')
def index():
    print('index')
    return 'ok'


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

4 如果before_request返回了

案例一：

before_request1返回

# -*- coding: utf-8 -*-
# @Time    : 2021/12/13 20:30
# @Author  : dzg

from flask import Flask

app = Flask(__name__)


@app.before_request
def before_request1():
    print('before_request1')

    return 'before_request1'


@app.before_request
def before_request2():
    print('before_request2')


@app.after_request
def after_request1(response):
    print('after_request1')

    return response


@app.after_request
def after_request2(response):
    print('after_request2')

    return response


@app.route('/')
def index():
    print('index')
    return 'ok'


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

案例2：

before_request2返回

# -*- coding: utf-8 -*-
# @Time    : 2021/12/13 20:30
# @Author  : dzg

from flask import Flask

app = Flask(__name__)


@app.before_request
def before_request1():
    print('before_request1')


@app.before_request
def before_request2():
    print('before_request2')
    return 'before_request2'


@app.after_request
def after_request1(response):
    print('after_request1')

    return response


@app.after_request
def after_request2(response):
    print('after_request2')

    return response


@app.route('/')
def index():
    print('index')
    return 'ok'


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