自定义中间件

一、自定义中间件

"""
@author RansySun
@create 2019-12-16-19:08
"""
from flask import Flask, flash, get_flashed_messages, request

app = Flask(__name__)


class MyMiddleware:
    """
    实现自定义中间件

    """
    def __init__(self, wsgi_app123):
        self.wsgi_app123 = wsgi_app123

    def __call__(self, environ, start_response):
        print("request请求进来之前，请求来定义中间件")
        res = self.wsgi_app123(environ, start_response)
        print("response之后返回页面，请求走时定义中间件")
        print(res)
        return res
    	"""
    	结果：
    	request请求进来之前
		response之后返回页面
		<werkzeug.wsgi.ClosingIterator object at 0x03D81850>
    	"""

	@app.route('/index')
	def index():
    	# request.method
    	# session['sd']

    	return "中间件实现"
if __name__ == '__main__':
    app.wsgi_app = MyMiddleware(app.wsgi_app)
    # app.__call__()
    app.run()

总结：

1. 实现自定义中间在执行在app执行前和执行后执行,查看源码可以知道

   # app.__call__()
   
       def __call__(self, environ, start_response):
           """The WSGI server calls the Flask application object as the
           WSGI application. This calls :meth:`wsgi_app` which can be
           wrapped to applying middleware."""
           return self.wsgi_app(environ, start_response)
        def wsgi_app(self, environ, start_response):
               """The actual WSGI application. This is not implemented in
           :meth:`__call__` so that middlewares can be applied without
           losing a reference to the app object. Instead of doing this::
   
               app = MyMiddleware(app)
   
           It's a better idea to do this instead::
   
               app.wsgi_app = MyMiddleware(app.wsgi_app)
   
           Then you still have the original application object around and
           can continue to call methods on it.
   
           .. versionchanged:: 0.7
               Teardown events for the request and app contexts are called
               even if an unhandled error occurs. Other events may not be
               called depending on when an error occurs during dispatch.
               See :ref:`callbacks-and-errors`.
   
           :param environ: A WSGI environment.
           :param start_response: A callable accepting a status code,
               a list of headers, and an optional exception context to
               start the response.
           """
               pa