flask-信号

flask-信号
Flask框架中的信号基于blinker，其主要就是让开发者可是在flask请求过程中定制一些用户行为。

pip3 install blinker
1. 内置信号

request_started = _signals.signal(‘request-started‘) # 请求到来前执行
request_finished = _signals.signal(‘request-finished‘) # 请求结束后执行

before_render_template = _signals.signal(‘before-render-template‘) # 模板渲染前执行
template_rendered = _signals.signal(‘template-rendered‘) # 模板渲染后执行

got_request_exception = _signals.signal(‘got-request-exception‘) # 请求执行出现异常时执行

request_tearing_down = _signals.signal(‘request-tearing-down‘) # 请求执行完毕后自动执行（无论成功与否）
appcontext_tearing_down = _signals.signal(‘appcontext-tearing-down‘)# 应用上下文执行完毕后自动执行（无论成功与否）

appcontext_pushed = _signals.signal(‘appcontext-pushed‘) # 应用上下文push时执行
appcontext_popped = _signals.signal(‘appcontext-popped‘) # 应用上下文pop时执行
message_flashed = _signals.signal(‘message-flashed‘) # 调用flask在其中添加数据时，自动触发

class Flask(_PackageBoundObject):

    def full_dispatch_request(self):
       
        self.try_trigger_before_first_request_functions()
        try:
            # ############### 触发request_started 信号 ###############
            request_started.send(self)       
            rv = self.preprocess_request()
            if rv is None:
                rv = self.dispatch_request()
        except Exception as e:
            rv = self.handle_user_exception(e)
        response = self.make_response(rv)
        response = self.process_response(response)

        # ############### request_finished 信号 ###############
        request_finished.send(self, response=response)
        return response

    def wsgi_app(self, environ, start_response):
        
        ctx = self.request_context(environ)
        ctx.push()
        error = None
        try:
            try:
                response = self.full_dispatch_request()
            except Exception as e:
                error = e
                response = self.make_response(self.handle_exception(e))
            return response(environ, start_response)
        finally:
            if self.should_ignore_error(error):
                error = None
            ctx.auto_pop(error)

request_started