Flask generic exception handler unable to catch 405 error
Question
I've created an exception handler according to this piece of documentation :
import json
from flask import Blueprint, abort, current_app, jsonify, make_response, request
from werkzeug.exceptions import HTTPException
import pmo.service as pmo
ops = Blueprint("ops", __name__)
@ops.route("/today", methods=["GET"])
def get_today():
current_app.logger.info("Getting an entry for 'today'")
try:
return jsonify(pmo.get_today_entry())
except IndexError:
abort(404, "No entry for today")
@ops.errorhandler(Exception)
def handle_exception(e):
# pass through HTTP errors as json
if isinstance(e, HTTPException):
response = e.get_response()
payload = json.dumps({
"code": e.code,
"name": e.name,
"description": e.description,
})
response.data = f"{payload}\n"
response.content_type = "application/json"
return make_response(response, e.code)
# now handle non-HTTP exceptions only
response_body = {"code": 500, "message": "unhandled exception occurred", "details": str(e)}
return make_response(response_body, 500)
I decided to use this approach because I'm developing a REST api and wanted to get rid of any html responses. Still when I issue a POST request in order to trigger a 405 error it is being returned as html document and not json:
❯ curl -X POST localhost:5000/today
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 3.2 Final//EN">
<title>405 Method Not Allowed</title>
<h1>Method Not Allowed</h1>
<p>The method is not allowed for the requested URL.</p>
While GET request is handled as expected:
❯ curl localhost:5000/today
{"code": 404, "name": "Not Found", "description": "No entry for a given day"}
In fact the error handler is not being invoked on 405, I've verified that with a debugger.
What am I doing wrong?
3 answers
solution1
2 ACCPTED 2020-11-24 22:07:45
Your error handler needs to be on the app object, not the blueprint. Try:
@app.errorhandler(Exception)
def handle_exception(e):
...
Other than that, I don't see anything problematic about your code.
solution2
1 2020-11-24 21:13:37
As @KenKinder kindly pointed out in the comment the problem was in the placement of the generic exception handler. After moving it to application's entrypoint it started to work like a charm.
solution3
0 2022-12-08 10:08:22
Already answered, it needs to go on the @app but some further details:
In Modular Applications with Blueprints, most error handlers will work as expected. However, there is a caveat concerning handlers for 404 and 405 exceptions.
This is because the blueprint does not “own” a certain URL space, so the application instance has no way of knowing which blueprint error handler it should run if given an invalid URL.
Documentation for this: https://flask.palletsprojects.com/en/2.2.x/errorhandling/#blueprint-error-handlers
The technical post webpages of this site follow the CC BY-SA 4.0 protocol. If you need to reprint, please indicate the site URL or the original address.Any question please contact:yoyou2525@163.com.