REST Api¶
flask-peewee comes with some tools for exposing your project’s models via a
RESTful API. There are several components to the rest
module, but the basic
setup is to create an instance of RestAPI
and then register your
project’s models with subclasses of RestResource
.
Each RestResource
you expose via the API will support, by default,
the following:
- /api/<model name>/ – GET and POST requests
- /api/<model name>/<primary key>/ – GET, PUT and DELETE requests
Also, you can filter results by columns on the model using django-style syntax, for example:
- /api/blog/?name=Some%20Blog
- /api/blog/?author__username=some_blogger
Getting started with the API¶
In this documentation we’ll start with a very simple API and build it out. The complete version of this API is included in the example-app, so feel free to refer there.
The project will be a simple ‘twitter-like’ app where users can post short messages and “follow” other users.
Note
If you’re using apache with mod_wsgi and would like to use any of
the auth backends that use basic auth, you will need to add the following
directive: WSGIPassAuthorization On
Project models¶
There are three main models - User
, Relationship
and Message
- which
we will expose via the API. Here is a truncated version of what they look like:
from flask_peewee.auth import BaseUser
class User(db.Model, BaseUser):
username = CharField()
password = CharField()
email = CharField()
join_date = DateTimeField(default=datetime.datetime.now)
active = BooleanField(default=True)
admin = BooleanField(default=False)
class Relationship(db.Model):
from_user = ForeignKeyField(User, related_name='relationships')
to_user = ForeignKeyField(User, related_name='related_to')
class Message(db.Model):
user = ForeignKeyField(User)
content = TextField()
pub_date = DateTimeField(default=datetime.datetime.now)
Creating a RestAPI¶
The RestAPI
acts as a container for the various RestResource
objects we will expose. By default it binds all resources to /api/<model-name>/
.
Here we’ll create a simple api and register our models:
from flask_peewee.rest import RestAPI
from app import app # our project's Flask app
# instantiate our api wrapper
api = RestAPI(app)
# register our models so they are exposed via /api/<model>/
api.register(User)
api.register(Relationship)
api.register(Message)
# configure the urls
api.setup()
Now if we hit our project at /api/message/
we should get something like the following:
{
"meta": {
"model": "message",
"next": "",
"page": 1,
"previous": ""
},
"objects": [
{
"content": "flask and peewee, together at last!",
"pub_date": "2011-09-16 18:36:15",
"user_id": 1,
"id": 1
},
{
"content": "Hey, I'm just some user",
"pub_date": "2011-09-16 18:46:59",
"user_id": 2,
"id": 2
}
]
}
Say we’re interested in the first message, we can hit /api/message/1/
to view
just the details on that object:
{
content: "flask and peewee, together at last!"
pub_date: "2011-09-16 18:36:15"
user_id: 1
id: 1
}
Customizing what is returned¶
If you access the User
API endpoint, we quickly notice a problem:
$ curl http://127.0.0.1:5000/api/user/
{
"meta": {
"model": "user",
"next": "",
"page": 1,
"previous": ""
},
"objects": [
{
"username": "admin",
"admin": true,
"email": "",
"join_date": "2011-09-16 18:34:49",
"active": true,
"password": "d033e22ae348aeb5660fc2140aec35850c4da997",
"id": 1
},
{
"username": "coleifer",
"admin": false,
"email": "coleifer@gmail.com",
"join_date": "2011-09-16 18:35:56",
"active": true,
"password": "a94a8fe5ccb19ba61c4c0873d391e987982fbbd3",
"id": 2
}
]
}
Passwords and email addresses are being exposed. In order to exclude these fields
from serialization, subclass RestResource
:
from flask_peewee.rest import RestAPI, RestResource
from app import app # our project's Flask app
# instantiate our api wrapper
api = RestAPI(app)
# create a special resource for users that excludes email and password
class UserResource(RestResource):
exclude = ('password', 'email',)
# register our models so they are exposed via /api/<model>/
api.register(User, UserResource) # specify the UserResource
api.register(Relationship)
api.register(Message)
Now emails and passwords are no longer returned by the API.
Allowing users to post objects¶
What if we want to create new messages via the Api? Or modify/delete existing messages?
$ curl -i -d '' http://127.0.0.1:5000/api/message/
HTTP/1.0 401 UNAUTHORIZED
WWW-Authenticate: Basic realm="Login Required"
Content-Type: text/html; charset=utf-8
Content-Length: 21
Server: Werkzeug/0.8-dev Python/2.6.6
Date: Thu, 22 Sep 2011 16:14:21 GMT
Authentication failed
The authentication failed because the default authentication mechanism only allows read-only access.
In order to allow users to create messages via the API, we need to use a subclass
of Authentication
that allows POST
requests. We also want to ensure
that the requesting user is a member of the site.
For this we will use the UserAuthentication
class as the default auth
mechanism.
from auth import auth # import the Auth object used by our project
from flask_peewee.rest import RestAPI, RestResource, UserAuthentication
# create an instance of UserAuthentication
user_auth = UserAuthentication(auth)
# instantiate our api wrapper, specifying user_auth as the default
api = RestAPI(app, default_auth=user_auth)
# create a special resource for users that excludes email and password
class UserResource(RestResource):
exclude = ('password', 'email',)
# register our models so they are exposed via /api/<model>/
api.register(User, UserResource) # specify the UserResource
api.register(Relationship)
api.register(Message)
# configure the urls
api.setup()
Now we should be able to POST new messages.
import json
import httplib2
sock = httplib2.Http()
sock.add_credentials('admin', 'admin') # use basic auth
message = {'user_id': 1, 'content': 'hello api'}
msg_json = json.dumps(message)
headers, resp = sock.request('http://localhost:5000/api/message/', 'POST', body=msg_json)
response = json.loads(resp)
The response object will look something like this:
{
'content': 'hello api',
'user_id': 1,
'pub_date': '2011-09-22 11:25:02',
'id': 3
}
There is a problem with this, however. Notice how the user_id
was passed in
with the POST data? This effectively will let a user post a message as another user.
It also means a user can use PUT requests to modify another user’s message:
# continued from above script
update = {'content': 'haxed you, bro'}
update_json = json.dumps(update)
headers, resp = sock.request('http://127.0.0.1:5000/api/message/2/', 'PUT', body=update_json)
response = json.loads(resp)
The response will look like this:
{
'content': 'haxed you, bro',
'pub_date': '2011-09-16 18:36:15',
'user_id': 2,
'id': 2
}
This is a problem – we need a way of ensuring that users can only edit their own messages. Furthermore, when they create messages we need to make sure the message is assigned to them.
Restricting API access on a per-model basis¶
flask-peewee comes with a special subclass of RestResource
that
restricts POST/PUT/DELETE requests to prevent users from modifying another user’s
content.
from flask_peewee.rest import RestrictOwnerResource
class MessageResource(RestrictOwnerResource):
owner_field = 'user'
api.register(Message, MessageResource)
Now, if we try and modify the message, we get a 403 Forbidden:
headers, resp = sock.request('http://127.0.0.1:5000/api/message/2/', 'PUT', body=update_json)
print headers['status']
# prints 403
It is fine to modify our own message, though (message with id=1):
headers, resp = sock.request('http://127.0.0.1:5000/api/message/1/', 'PUT', body=update_json)
print headers['status']
# prints 200
Under-the-hood, the implementation of the RestrictOwnerResource
is pretty simple.
- PUT / DELETE – verify the authenticated user is the owner of the object
- POST – assign the authenticated user as the owner of the new object
Locking down a resource¶
Suppose we want to restrict normal users from modifying User
resources. For this
we can use a special subclass of UserAuthentication
that restricts access
to administrators:
from flask_peewee.rest import AdminAuthentication
# instantiate our user-based auth
user_auth = UserAuthentication(auth)
# instantiate admin-only auth
admin_auth = AdminAuthentication(auth)
# instantiate our api wrapper, specifying user_auth as the default
api = RestAPI(app, default_auth=user_auth)
# register the UserResource with admin auth
api.register(User, UserResource, auth=admin_auth)
Filtering records and querying¶
A REST Api is not very useful if it cannot be queried in a meaningful fashion. To
this end, the flask-peewee RestResource
objects support “django-style”
filtering:
$ curl http://127.0.0.1:5000/api/message/?user=2
This call will return only messages by the User
with id=2:
{
"meta": {
"model": "message",
"next": "",
"page": 1,
"previous": ""
},
"objects": [
{
"content": "haxed you, bro",
"pub_date": "2011-09-16 18:36:15",
"user_id": 2,
"id": 2
}
]
}
Joins can be traversed using the django double-underscore notation:
$ curl http://127.0.0.1:5000/api/message/?user__username=admin
{
"meta": {
"model": "message",
"next": "",
"page": 1,
"previous": ""
},
"objects": [
{
"content": "flask and peewee, together at last!",
"pub_date": "2011-09-16 18:36:15",
"user_id": 1,
"id": 1
},
{
"content": "hello api",
"pub_date": "2011-09-22 11:25:02",
"user_id": 1,
"id": 3
}
]
}
It is also supported to use different comparison operators with the same double-underscore notation:
$ curl http://127.0.0.1:5000/api/user/?user__lt=2
{
"meta": {
"model": "user",
"next": "",
"page": 1,
"previous": ""
},
"objects": [{
"username": "admin",
"admin": true,
"email": "admin@admin",
"active": true,
"password": "214de$25",
"id": 1
}]
}
- Valid Comparison Operators are:
- ‘eq’, ‘lt’, ‘lte’, ‘gt’, ‘gte’, ‘ne’, ‘in’, ‘is’, ‘like’, ‘ilike’
Sorting results¶
Results can be sorted by specifying an ordering
as a GET argument. The ordering
must be a column on the model.
/api/message/?ordering=pub_date
If you would like to order objects “descending”, place a “-” (hyphen character) before the column name:
/api/message/?ordering=-pub_date
Limiting results and pagination¶
By default, resources are paginated 20 per-page. If you want to return less, you
can specify a limit
in the querystring.
/api/message/?limit=2
In the “meta” section of the response, URIs for the “next” and “previous” sets of results are available:
meta: {
model: "message"
next: "/api/message/?limit=1&page=3"
page: 2
previous: "/api/message/?limit=1&page=1"
}