python before_request详解

before_request 顾名思义，就是在request请求之前做的事情。
它会在每一个请求来的时候，都会先去请求before_request注册的函数。
before_request需要注册一个函数，可以不需要参数。
这个示例是在每个请求之前，做一个分类，不同环境来源的请求需要做
不同的事情。

演示代码

from flask import Flask,request
app = Flask(__name__)

@app.route("/test1", methods=['POST'])
def t1():
    data = request.get_json(force=True)
    env = data.get('env')
    print(env)
    return env
	
@app.route("/test2")
def t2():
    env = request.args.get('env')
    print(env)
    return env
	
@app.before_request
def before():
    res_method = request.method
    env = ''
    if res_method == 'GET':
        env = request.args.get('env')
    if res_method == 'POST':
        data = request.get_json(force=True)
        env = data.get('env')
    if env == 't1':
        print('before t1, I need change nginx')
    elif env == 't2':
        print('before t2,I need to update mysql')
    else:
        print('new env: %s, I need check it' % env)
    return None
if __name__ == "__main__":
    app.run()

结果演示
C:\Users\jh>curl -H "Content-type: application/json" -d "{\"env\":\"t1\"}" http://127.0.0.1:5000/test1
t1
C:\Users\jh>curl http://127.0.0.1:5000/test2?env=t2
t2
C:\Users\jh>curl http://127.0.0.1:5000/test2?env=t7
t7

后台日志输出
127.0.0.1 - - [26/Aug/2022 19:41:28] "POST /test1 HTTP/1.1" 200 -
before t1, I need change nginx
t1
127.0.0.1 - - [26/Aug/2022 19:41:36] "GET /test2?env=t2 HTTP/1.1" 200 -
before t2,I need to update mysql
t2
127.0.0.1 - - [26/Aug/2022 19:41:40] "GET /test2?env=t7 HTTP/1.1" 200 -
new env: t7, I need check it
t7

before_request通常使用在验证登录，过滤请求攻击等方面

详细文档
https://dormousehole.readthedocs.io/en/latest/api.html#flask.Flask.before_request