Exceptions and HTTP status codes

In many situations, you might want to use common HTTP status codes to indicate the success or failure of a user's API request. For example, if a user is attempting to retrieve an entity which doesn't exist, you might want to send an HTTP 404 status code to say that no entity with the ID entity_id exists.

You can send such common HTTP status codes by raising an exception provided by the endpoints library as follows:

message = 'No entity with the id "%s" exists.' % entity_id
raise endpoints.NotFoundException(message)

Exceptions provided by Endpoints Frameworks

The endpoints library provides the following exceptions, corresponding to specific HTTP status codes:

Exception	Corresponding HTTP status code
`endpoints.BadRequestException`	HTTP 400
`endpoints.UnauthorizedException`	HTTP 401
`endpoints.ForbiddenException`	HTTP 403
`endpoints.NotFoundException`	HTTP 404
`endpoints.InternalServerErrorException`	HTTP 500

Supported HTTP status codes

Cloud Endpoints Frameworks supports a subset of HTTP status codes in API responses. The following table describes the supported codes.

HTTP status codes	Support
HTTP 2xx	HTTP `200` is typically assumed by Endpoints Frameworks if the API method returns successfully. If the API method response type is `VoidMessage` or the return value of the API method is `None` , HTTP `204` is set instead.
HTTP 3xx	HTTP 3xx codes aren't supported. Use of any HTTP 3xx codes results in an HTTP `404` response.
HTTP 4xx	Only the following HTTP 4xx codes are supported: `400` `401` `403` `404` `409` `410` `412` `413` Any other HTTP 4xx codes are returned as error `404`, except for the following: `405` is returned as `501` `408` is returned as `503`
HTTP 5xx	All HTTP 5xx status codes are converted to HTTP `503` in the client response.

Creating your own exception classes

If you want to create other exception classes for other HTTP status codes, you can do so by subclassing endpoints.ServiceException. The following snippet shows how to create an exception class that represents an HTTP 409 status code:

import endpoints
import httplib

class ConflictException(endpoints.ServiceException):
  """Conflict exception that is mapped to a 409 response."""
  http_status = httplib.CONFLICT