table of Contents
flask request extension
The request extension in flask is equivalent to middleware in django
#flask里面的请求扩展相当于django中的中间件
from flask import Flask,request
app = Flask(__name__)
@app.before_request
def before1():
print("我是befor1")
return "ok"
@app.before_request
def before2():
print("我是befor2")
@app.after_request
def after1(response):
print("响应后的参数",response)
print("我是after1")
return response
@app.after_request
def after2(response):
print("我是after2")
return response
@app.before_first_request
def first():
print("我是第一次")
@app.route("/")
def index():
print("我是响应函数")
return "ok"
if __name__ == '__main__':
app.run()
The execution order of the response function:
The order of execution before the response function
The order of execution after the response function
after_request must receive a parameter, which is a response object, and must return
Summary (the order of execution is numbered below)
1 before_first_request 当项目启动后，接收到的第一个请求，就会执行before_first_request装饰的函数，执行顺序也是谁先注册就谁先执行
2 before_request 请求没有经过响应函数的时候，会执行before_request装饰的函数，谁先注册谁先执行。只要有一个函数有返回值，后面的所有before_request都不会执行，且响应函数也不会执行。其有没有返回值都不会影响after_request的执行
3 after_request是再before_request与响应函数执行后执行。他必须接收响应参数，并且要把响应返回。执行顺序是谁先注册后执行。
Request extended error handling
- teardown_request is used to catch errors. It will be executed regardless of whether there is an error. If there is no error, the error received is none, and if there is an error, the error is received. But it cannot handle errors.
- Errorhandler (error status code), for different status codes, execute different functions, no error will not be executed, if there is an error, it will handle the error.
from flask import Flask,request,render_template
app = Flask(__name__)
@app.teardown_request
def tear(e):
print(e)
print("我是teardown_request")
@app.errorhandler(500)
def error_500(e):
print(e)
return "我程序崩了，你下次来把"
@app.errorhandler(404)
def error_404(e):
print(e)
return render_template("404.html")
@app.route("/")
def index():
print("我是响应函数")
return render_template("index.html")
if __name__ == '__main__':
app.run()
to sum up:
1 teardown_request,一旦遇到错误就会执行，并且把错误传递给teardown_request装饰的函数, 没有错误也会执行，但是是错误为None,他并不能处理错误，只能记录
2 errorhandle 可以捕获错误，并且对错误做出响应，返回给用户,如果你要用errorhandler你必须指定他捕获哪种类型的错误，就必须传错误码，然后就返回值，返回给用户
Request extended tags and filters
from flask import Flask,request,render_template
app = Flask(__name__)
#相当于django中的标签。
@app.template_global()
def get_sb(a1,a2):
return a1 + a2
#再html中的用法{{get_sb(1,2)}}
#django中的过滤器,以一个参数是你要过滤的那个值
@app.template_filter()
def get_something(a1,a2,a3,a4):
return a1+a2+a3+a4
#再html中{{1|4，2，3}}
@app.route("/")
def index():
print("我是响应函数")
return render_template("index.html")
if __name__ == '__main__':
app.run()