Response Handling

Response Serialization

If the endpoint returns a Response object this response will be used as is.

Otherwise, and by default and if the specification defines that an endpoint produces only JSON, connexion will automatically serialize the return value for you and set the right content type in the HTTP header.

If the endpoint produces a single non-JSON mimetype then Connexion will automatically set the right content type in the HTTP header.

Customizing JSON encoder

Connexion allows you to customize the JSONEncoder class in the Flask app instance json_encoder (connexion.App:app). If you wanna reuse the Connexion’s date-time serialization, inherit your custom encoder from connexion.apps.flask_app.FlaskJSONEncoder.

Returning status codes

There are two ways of returning a specific status code.

One way is to return a Response object that will be used unchanged.

The other is returning it as a second return value in the response. For example

def my_endpoint():
    return 'Not Found', 404

Returning Headers

There are two ways to return headers from your endpoints.

One way is to return a Response object that will be used unchanged.

The other is returning a dict with the header values as the third return value in the response:

For example

def my_endpoint():
    return 'Not Found', 404, {'x-error': 'not found'}

Response Validation

While, by default Connexion doesn’t validate the responses it’s possible to do so by opting in when adding the API:

import connexion

app = connexion.FlaskApp(__name__, specification_dir='swagger/')
app.add_api('my_api.yaml', validate_responses=True)
app.run(port=8080)

This will validate all the responses using jsonschema and is specially useful during development.

Custom Validator

By default, response body contents are validated against OpenAPI schema via connexion.decorators.response.ResponseValidator, if you want to change the validation, you can override the default class with:

validator_map = {
    'response': CustomResponseValidator
}
app = connexion.FlaskApp(__name__, ..., validator_map=validator_map)

Error Handling

By default connexion error messages are JSON serialized according to Problem Details for HTTP APIs

Application can return errors using connexion.problem.