Hook Extension Point

Description

The extension point abbreviation is hep.

This extension point works in the flask hook function and currently supports three hooks with the following names:

  • before_request

    Before request (intercept requests are allowed)

  • after_request

    After request (no exception before return)

  • teardown_request

    After request (before return, with or without exception)

  • before_first_request

    Registers a function to be run before the first request to this instance of the application.

Other hooks will be supported later, and a exception PEPError will be triggered if a hook name that is not supported by the current version is used.

The plugin needs to return the hep field via register. The hep data type returned is a dictionary with the format {hook_name: callable}, which can have multiple hep_names.

The Flask-PluginKit loads hep via _hep_handler(), this method will detect hep rules and specific content.

Similar to tep, each hook_name has many values for the entire web application.

When in use, the user does not care how to call, because Flask-PluginKit has registered the hook handler at initialization time, but it should be noted that there are different requirements for different hook type handlers:

  • before_request

    This is simple, any callback function, class method, and so on can be used, there is no parameter, but the hook function here has a special place. As we all know, for Flask, if the before_request return value is not None, the request will be terminated. So Flask-PluginKit will try to detect the return value of the hook function, if it is not None, it will return, and the request is terminated at this moment.

  • after_request

    Will pass a response parameter, this is the web application response data, is an instance of Response, the function corresponding to this hook can get response, you can not return response.

  • teardown_request

    Similar to after_request, this hook is triggered by the flask when the web exception occurs. Flask-PluginKit will pass the exception parameter to the corresponding hook function without returning.

  • before_first_request

    Refer before_request, run only once after the app starts, no return value.

Example

  • Plugin registration for hep
from flask import request, g, current_app

def set_login_state():
    g.login_in = request.args.get("username") == "admin" and \
                 request.args.get("password") == "admin

def record_access_log(response):
    log = {
        "status_code": response.status_code,
        "method": request.method,
        "ip": request.headers.get('X-Real-Ip', request.remote_addr),
        "url": request.url,
        "referer": request.headers.get('Referer'),
        "agent": request.headers.get("User-Agent"),
        "login_in": g.login_in
    }
    current_app.logger.info(log)

def register():
    return dict(
        hep=dict(
            before_request=set_login_state,
            after_request=record_access_log
        )
    )

As above, after your program is running, the set_login_state function will be executed before each request, and the record_access_log function will be executed before the request returns.