Request hooks are a convenient way of performing actions before and after a request is processed by your code. There are several types of request hooks:
- Global-level request hooks, which take action on ALL routes. These can be technically seen as root blueprint-level hooks, since they act on the root blueprint.
- Blueprint-level request hooks, which take action at the blueprint level. These are registered on a blueprint, and act on all routes registered to that blueprint, as well as all routes registered to children blueprints.
- Route-level request hooks, which take action on individual routes.
All hooks must complete successfully. If any hook fails, then the request will fail with a 500 Internal Server Error.
Note
Global-level hooks are registered with app.add_hook and family, but actually redirect to the root blueprint.
Adding a hook can be done with add_hook() or add_hook(). These take a type param and
a the hook function to add.
Alternatively, you can use the helper functions:
Blueprint.before_request(func)[source]Convenience decorator to add a pre-request hook.
Route.before_request(func)[source]Convenience decorator to add a post-request hook.
Blueprint.after_request(func)[source]Convenience decorator to add a post-request hook.
Route.after_request(func)[source]Convenience decorator to add a pre-request hook.
Pre-request hooks are hooks that are fired before a request handler is invoked. They are fired in the order they are added.
Pre-request hooks take one param: the HTTPRequestContext that the request is going to be invoked with. They
can either return the modified context, a new context, or None to use the previous context as the new one.
async def print_request(ctx: HTTPRequestContext):
print("Request for", ctx.request.path)
return ctx # can be omitted to leave `ctx` in place
Post-request hooks are hooks that are fired after a request is invoked. They are fired in the order they are added.
Post-request hooks take two params: The HTTPRequestContext that the request was invoked with, and the
wrapped result (NOT the final result!) of the response handler. They can either return a modified Response,
or None to use the previous Response as the new one.
async def jsonify(ctx, response):
if not isinstance(response.response, dict):
return response
r.set_data(json.dumps(response.response))
return r