REST interface for NDB models over webapp2 in Google App Engine Python
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README.md

rest_gae

REST interface for NDB models over webapp2 in Google App Engine Python.

About

Written and maintained by Yaron Budowski. Email me at: budowski@gmail.com. Code contributed by dankrause.

A lot of authentication-related code was taken from webapp2-user-accounts by abahgat.

To be used with Apache v2 license. Though it would be nice to hear about projects using this library (email me :-D).

Example

from rest_gae import *
from rest_gae.users import UserRESTHandler

class MyModel(ndb.Model):
  property1 = ndb.StringProperty()
  property2 = ndb.StringProperty()
  owner = ndb.KeyPropertyProperty(kind='User')
  
  class RESTMeta:
    user_owner_property = 'owner' # When a new instance is created, this property will be set to the logged-in user
    include_output_properties = ['property1'] # Only include these properties for output
  
app = webapp2.WSGIApplication([
    # Wraps MyModel with full REST API (GET/POST/PUT/DELETE)
    RESTHandler(
      '/api/mymodel', # The base URL for this model's endpoints
      MyModel, # The model to wrap
      permissions={
        'GET': PERMISSION_ANYONE,
        'POST': PERMISSION_LOGGED_IN_USER,
        'PUT': PERMISSION_OWNER_USER,
        'DELETE': PERMISSION_ADMIN
      },
      
      # Will be called for every PUT, right before the model is saved (also supports callbacks for GET/POST/DELETE)
      put_callback=lambda model, data: model
    ),

    # Optional REST API for user management
    UserRESTHandler(
        '/api/users',
        user_model=MyUser, # You can extend it with your own custom user class
        user_details_permission=PERMISSION_OWNER_USER,
        verify_email_address=True,
        verification_email={
            'sender': 'John Doe <john@doe.com>',
            'subject': 'Verify your email address',
            'body_text': 'Click here {{ user.full_name }}: {{ verification_url }}',
            'body_html': '<a href="{{ verification_url }}">Click here</a> {{ user.full_name }}'
            },
        verification_successful_url='/verification_successful',
        verification_failed_url='/verification_failed',
        reset_password_url='/reset_password',
        reset_password_email={
            'sender': 'John Doe <john@doe.com>',
            'subject': 'Please reset your password',
            'body_text': 'Reset here: {{ verification_url }}',
            'body_html': '<a href="{{ verification_url }}">Click here</a> to reset'
            },
        )
], debug=True, config=config)

Features

REST API
  • GET/POST/PUT/DELETE endpoints for NDB models (over webapp2) - JSON input/output.
  • GET endpoint supports GQL querying, page fetching, ordering and results limits.
  • Individually set permissions for each endpoint (e.g. only admins can delete a model; only the owning user can edit a model)
  • When a model instance is created (using POST) - Automatically sets its owning user property
  • Set which model properties should be included/excluded for REST endpoints
  • Property name customization (e.g. "myprop" will be shown as "my_fancy_prop")
  • Callback functions to be called during GET/POST/PUT/DELETE (for extra functionality/customization)
  • Support for BlobKeyProperty
  • Using custom string IDs for models
  • X-HTTP-Method-Override support
  • CORS support
  • Supports any webapp2 authentication compatible mechanism
User Management REST API
  • Also includes a REST API for user management (to be used with rest_gae)
  • GET/POST/PUT/DELETE endpoints for users
  • Support for admin users (can manipulate other users' details freely)
  • Can customize the built-in user class with additional properties
  • Email verification (sends emails using GAE's email services or any other 3rd-party service)
  • Password reset (by sending emails)
  • Password policy enforcement

Installation

  1. Configure webapp2 for GAE
  2. Configure Jinja2 for GAE
  3. Include dateutil with your app (make sure import dateutil works) - this is optional (will use datetime.strptime otherwise) - if not used, the library will be less tolerant to input date string parsing
  4. Drop-in the rest_gae folder

Documentation

RESTHandler

Should be used as part of the WSGIApplication routing:

from rest_gae import * # This imports RESTHandler and the PERMISSION_ constants

app = webapp2.WSGIApplication([
    RESTHandler(
        '/api/mymodel', # The base API for this model's endpoints
        MyModel, # The model to wrap (can also be a string - e.g. `models.MyModel`)
        permissions={
            'GET': PERMISSION_ANYONE,
            'POST': PERMISSION_LOGGED_IN_USER,
            'PUT': PERMISSION_OWNER_USER,
            'DELETE': PERMISSION_ADMIN
        },
        allow_http_method_override=False,
        allowed_origin='*'
    )
])

The RESTHandler adds the following REST endpoints (according to permissions parameter):

  • GET /mymodel - returns all instances of MyModel (PERMISSION_ANYONE - all instances; PERMISSION_OWNER_USER - only the ones owned by the current logged-in user). See notes below on how to use the GET endpoint for advanced querying.
  • GET /mymodel/123 - returns information about a specific model instance (PERMISSION_OWNER_USER - only the owning user can view this information)
  • POST /mymodel - creates a new MyModel instance - supports multi-instance creation (just pass an array of models instead of a dict)
  • PUT /mymodel/123 - updates an existing model's properties (PERMISSION_OWNER_USER - only the owning user can do that)
  • PUT /mymodel - updates several model instances at once. The entire request is transactional - If one of the model update fails, any previous updates made in the same request will be undone.
  • DELETE /mymodel/123 - deletes a specific model (PERMISSION_OWNER_USER - only the owning user can do that)
  • DELETE /mymodel - PERMISSION_OWNER_USER: deletes all model instances owned by the currently logged-in user; PERMISSION_ADMIN - deletes all model instances

Arguments the RESTHandler class constructor accepts:

  • url - The base URL for all endpoints.
  • model - The model class (can also be a string) that should be wrapped
  • permissions - A dictionary of permissions (key=GET/POST/PUT/DELETE; value=PERMISSION_...). rest_gae uses webapp2_extras.auth to detect the currently logged-in user. Possible permissions:
    • PERMISSION_ANYONE - Anyone (even if not logged-in) can access this endpoint
    • PERMISSION_LOGGED_IN_USER - Must be a logged-in user to access this endpoint
    • PERMISSION_OWNER_USER - Must be the owner of the current model (used in PUT/DELETE endpoints). See notes below on how to specify the name of the Model property that marks the owning user.
    • PERMISSION_ADMIN - Must be an admin to access the current endpoint. See notes below on how to specify the name of the User model property that marks if a user is an admin or not.
  • after_get_callback - (optional) If set, this function will be called just before returning the results:
    • In case of a GET /mymodel - the argument will be a list of model instances. The function must return a list of models, not necessarily the same as the input list (it can also be an empty list).
    • In case of a GET /mymodel/123 - the argument will be a single model instance. The function must return the model.
  • before_post_callback - (optional) If set, this function will be called right after creating the model(s) according to the input JSON data, and right before saving it (i.e. before model.put()). It receives two arguments - the list of models which are going to be inserted into DB (can be one in the list); the raw input JSON dict (after it has gone through some pre-processing). The function must return the list of models to save. If the function raises an exception, the model creation fails with an error.
  • after_post_callback - (optional) If set, this function will be called right after saving the models according to the input JSON data, (i.e. after model.put()). The function receives two arguments: The keys of the models which were saved; the model instances which were be saved. The function must return the list of models to be returned as output for the endpoint.
  • before_put_callback - (optional) If set, this function will be called right after updating the model according to the input JSON data, and right before saving the updated model (i.e. before model.put()). The function receives two arguments: The list of models which will be saved; the raw input JSON dict (after it has gone through some pre-processing). The function must return the list of models, in order for them to be saved. If the function raises an exception, the model update fails with an error.
  • after_put_callback - (optional) If set, this function will be called right after updating the model(s) according to the input JSON data (i.e. after model.put()). The function receives two arguments: The keys of the models which were saved; the model instances which were be saved. The function must return the list of models to be returned as output for the endpoint.
  • before_delete_callback - (optional) If set, this function will be called right before deleting a model. Receives an input argument of the models to be deleted. The function returns the list of models to delete (may be an empty list). If the function raises an exception, the model deletion fails with an error.
  • after_delete_callback - (optional) If set, this function will be called right after deleting a model. Receives two input arguments of the keys of the deleted models + the models that were deleted. The function returns the list of models that will be returned as the endpoint output.
  • allow_http_method_override - (optional; default=True) If set, allows the user to add an HTTP request header 'X-HTTP-Method-Override' to override the request type (e.g. if the HTTP request is a POST but it also contains 'X-HTTP-Method-Override: GET', it will be treated as a GET request).
  • allowed_origin - (optional; default=None) If not set, CORS support is disabled. If set to '*' - allows Cross-Site HTTP requests from all domains; if set to 'http://sub.example.com' or similar - allows Cross-Site HTTP requests only from that domain. See here for more information.

Advanced Querying using GET Endpoint

The GET /mymodel endpoint queries all of the model instances (or only the logged-in user's models - in case of PERMISSION_OWNER_USER). The endpoint accepts the following GET arguments:

  • q - A GQL query. For example: (prop1 > 300) and (prop2 < 500). See here for more info and limitations. Note: a) Make sure you URL-encode the value of this parameter (e.g. (prop1=999) and (prop2>400) becomes %28prop1%3D999%29+and+%28prop2%3E400%29). b) If using the != operator in your query, make sure to use the order argument with the inequality property as the first order (e.g. if q=prop1 != 300 -> should use order=prop1).
  • order - The order to sort the results by. Can be a comma-delimited list of property names. If a property name is prefixed with a minus sign, it means reverse order. For example: prop1,-prop2,prop3.
  • limit - Indicates the maximum number of results to return (default = 1000).

The output of the GET endpoint looks like this:

{ "results": [ ... ],
  "next_results_url": "http://example.com/mymodel?q=prop%3E666&limit=100&cursor=E-ABAIICLmoVZGV2fnBlcnNvbmFsbnV0cml0aW9uchULEghBY3Rpdml0eRiAgICAgPDbCAwU" }
  • results - An array of results
  • next_results_url - In case limit results have been returned and more results are available - this URL points to the next batch of results (will be equal to null if no more results).

Using PERMISSION_ADMIN

In order for gae_rest to know if the currently logged-in user is an admin or not, rest_gae assumes the User model has a BooleanProperty that indicates it:

class MyUser(webapp2_extras.appengine.models.User):
    is_admin = ndb.BooleanProperty(default=False)
    
    class RESTMeta:
        # This is how rest_gae knows if a user is an admin or not
        admin_property = 'is_admin'

Note: If you choose to use the built-in UserRESTHandler for user management, there is no need to specify admin_property (since it uses the rest_gae.users.User model, which already includes this definition).

Using PERMISSION_OWNER_USER

If using PERMISSION_OWNER_USER, the model class MUST include a RESTMeta class with a user_owner_property defined. That property will be used in two cases:

  • When verifying the ownership of the model (e.g. PUT to a specific model that is not owned by the currently logged-in user).
  • When adding a new model (but not when updating) - that property will be assigned to the currently logged-in user. Note that this assignment works recursively for any StructuredProperty of the model (if that StructuredProperty's model has its own user_owner_property defined).
class MyModel(ndb.Model):
    # When creating a new MyModel instance (using POST), this property will be set to the logged-in user.
    # Also, when trying to update/delete this model (using PUT/DELETE), in case of `PERMISSION_OWNER_USER`,
    # we'll verify that the logged-in user is in fact the owner of the model.
    owner = ndb.KeyProperty(kind='MyUser')
    
    class RESTMeta:
        user_owner_property = 'owner'

Filter Properties

You can choose which model properties will be displayed as JSON output, and which properties will be accepted as input:

class MyModel(ndb.Model):
    prop1 = ndb.StringProperty()
    prop2 = ndb.StringProperty()
    prop3 = ndb.StringProperty()

    class RESTMeta:
        excluded_input_properties = ['prop1'] # Ignore input from users for these properties (these properties will be ignored on PUT/POST)
        excluded_output_properties = ['prop2'] # These properties won't be returned as output from the various endpoints
        excluded_properties = [ 'prop1', 'prop2' ] # Excluded properties - Both input and output together

        included_input_properties = ['prop1', 'prop3'] # Only these properties will be accepted as input from the user
        included_output_properties = ['prop1', 'prop3'] # Only these properties will returned as output
        included_properties = [ 'prop1', 'prop3' ] # Included properties - Both input and output together

Display Properties with a Different Name

You can define the names of properties, as they are displayed to the user or the way they're accepted as input:

class MyModel(ndb.Model):
    prop1 = ndb.StringProperty()
    prop2 = ndb.StringProperty()
    prop3 = ndb.StringProperty()

    class RESTMeta:
        # All endpoints will display 'prop1' as 'new_prop1' and 'prop3' as 'new_prop3'
        translate_output_property_names = { 'prop1': 'new_prop1', 'prop3': 'new_prop3' }
        # All endpoints will accept 'new_prop2' instead of 'prop2' as input
        translate_input_property_names = { 'prop2': 'new_prop2' }
        # Translation table - both for input and output
        translate_property_names = { ... }

Using BlobKeyProperty

In case your model uses a BlobKeyProperty, it can be read/written as following:

class MyModel(ndb.Model):
    prop1 = ndb.StringProperty()
    blob_prop = ndb.BlobKeyProperty()

When calling GET /api/my_model it'll return the following:

{ "results": [
    {
        "id": "ahFkZXZ-cmVzdGdhZXNhbXBsZXIUCxIHTXlNb2RlbBiAgICAgICgCAw",
        "prop1": "some value",
        "blob_prop": {
            "upload_url": "http://myapp.com/api/my_model/ahFkZXZ-cmVzdGdhZXNhbXBsZXIUCxIHTXlNb2RlbBiAgICAgICgCAw/blob_prop",
            "download_url": "http://myapp.com/api/my_model/ahFkZXZ-cmVzdGdhZXNhbXBsZXIUCxIHTXlNb2RlbBiAgICAgICgCAw/blob_prop"
        }
    }
    ...
]
}
  • upload_url - The URL to be used for uploading the blob data. This should be used as any other blob in GAE (see here) - a POST with a "multipart/form-data" enctype.
  • download_url - The URL you can GET in order to download the blob - This should be used as any other blob in GAE (see here) - a GET with optional byte-range header. If the blob property has no value set - this will be null.

Note: Blobs will be deleted when the model pointing to them is deleted and also when a new blob is uploaded (old blob is overwritten).

Specifying a String ID for Models

In case you want the user to specify the ID of the model instance (instead of using the default GAE key format - e.g. ahFkZXZ-cmVzdGdhZXNhbXBsZXIUCxIHTXlNb2RlbBiAgICAgICgCAw), you can use the following:

class MyModel(ndb.Model):
  property1 = ndb.StringProperty()
  
  class RESTMeta:
    use_input_id = True

Now POST /api/my_model will look like this:

{
    "id": "my_model_id",
    "property1": "some_val",
    ...
}

And the model-specific endpoints will look like this:

  • GET /api/my_model/my_model_id
  • PUT /api/my_model/my_model_id
  • DELETE /api/my_model/my_model_id

UserRESTHandler

Should be used as part of the WSGIApplication routing:

from rest_gae import * # This imports RESTHandler and the PERMISSION_ constants
from rest_gae.users import UserRESTHandler

# Make sure we initialize our WSGIApplication with this config (used for initializing webapp2_extras.sessions)
config = {}
config['webapp2_extras.sessions'] = {
    'secret_key': 'my-super-secret-key',
}

app = webapp2.WSGIApplication([
    UserRESTHandler(
        '/api/users', # The base URL for the user management endpoints
        user_model='models.MyUser', # Use our own custom User class
        email_as_username=True,
        admin_only_user_registration=True,
        user_details_permission=PERMISSION_LOGGED_IN_USER,
        verify_email_address=True,
        verification_email={
            'sender': 'John Doe <john@doe.com>',
            'subject': 'Verify your email',
            'body_text': 'Hello {{ user.full_name }}, click here: {{ verification_url }}',
            'body_html': 'Hello {{ user.full_name }}, click <a href="{{ verification_url }}">here</a>'
        },
        verification_successful_url='/verified-user',
        verification_failed_url='/verification-failed',
        reset_password_url='/reset-password',
        reset_password_email={
            'sender': 'John Doe <john@doe.com>',
            'subject': 'Reset your password',
            'body_text': 'Hello {{ user.name }}, click here: {{ verification_url }}',
            'body_html': 'Hello {{ user.name }}, click <a href="{{ verification_url }}">here</a>'
        },
        send_email_callback=my_send_email,
        allow_login_for_non_verified_email=False,
        user_policy_callback=lambda user, data: if len(data['password']) < 8: raise ValueError('Password too short')
   )], config=config)

This creates the following endpoints:

  • GET /users - returns the listing of all users (for admins only) - can be used as a standard rest_gae GET endpoint (with limit, order and q parameters).
  • GET /users/123 - get a specific user's details (permitted according to user_details_permission).
  • POST /users - registers a new user (if admin_only_user_registration == True - only admins can register).
  • POST /users/login - logins using an email/user name+password combination. Returns a cookie-based token to be used in later calls.
  • POST /users/reset - resets a user's password by sending him an email (the user name is passed in the POST data) - this endpoint is active only if verify_email_address is True.
  • GET /users/verify - when a user registers (in case verify_email_address is True), an email with a verification link is sent to him - this is that link. Also used for password reset.
  • DELETE /users/123 - Deletes a user account (permitted for admins or if the user deletes his own account).
  • PUT /users/123 - updates an existing user's details (permitted for admins or if the user updates his own account). This also allows password change.
  • Note: GET/POST/PUT/DELETE methods can be used with 'me' instead of the user ID (e.g. GET /users/me) as a shorthand for the currently logged-in user.

The UserRESTHandler constructor receives the following parameters:

  • user_model - (optional) The user model to be used - if omitted, uses the default rest_gae.users.User model. Note: This model MUST inherit from rest_gae.users.User model.
  • email_as_username - (optional; default=False) If true, will use the user's email as his user name.
  • admin_only_user_registration - (optional; default=False) Only admins can register new users. In this, internally, you can use the gae_rest.users.register_new_user utility function for creating users.
  • user_details_permission - (optional; default=PERMISSION_OWNER_USER) Defines who can view a specific user's details (anyone, any logged-in user, only the owning user or only admins).
  • verify_email_address - (optional; default=False) Verifies a user's email address - will send an email with a verification link (its user.is_email_verified will be False until then). The email is sent using GAE email services (see send_email_callback for using 3rd-party email sending services).
  • verification_email - (optional) Must be set if verify_email_address is True. A dict containing the details of the verification email being sent:
    • sender - The sender's email address (in the format of John Doe <john@doe.com>). Must be an authorized GAE sender (i.e. that email address must be registered as the app's developer/owner).
    • subject - The email's subject line
    • body_text - The email's text content - a Jinja2 compatible template. Receives two input arguments: user and verification_url.
    • body_html - The email's HTML content - a Jinja2 compatible template. Receives two input arguments: user and verification_url.
  • verification_successful_url - (optional) Must be set if verify_email_address is True. The URL that the user will be redirected to after clicking the email verification link and successfully verifying his email address.
  • verification_failed_url - (optional) Must be set if verify_email_address is True. The URL that the user will be redirected to after clicking the email verification link, while the verification failed (happens when the link is outdated or the input params are invalid).
  • reset_password_url - (optional) Must be set if verify_email_address is True. The URL that the user will be redirected to after clicking the reset password link. This page must show the user a new password form. When submitted, that page must call the PUT /users/123 endpoint and update the password. It also has to provide that endpoint an additional signup_token parameter - so that we'll delete that token once the password has been set (so that the reset password link that wasn sent won't be active any more).
  • reset_password_email - (optional) Must be set if verify_email_address is True. A dict containing the details of the reset password email being sent: Contains the same details as the verification_email dict.
  • send_email_callback - (optional) If set, we'll use this function for sending out the emails for email verification / password reset (instead of using GAE's email services). The function receives a single dict argument - containing sender, subject, body_text, body_html. Note: The body_text + body_html values are already rendered as templates (meaning, the verification URLs are already embedded inside them).
  • allow_login_for_non_verified_email - (optional; default=True) If set to False, any user with a non-verified email address will not be able to login (will get an access denied error).
  • user_policy_callback - (optional) If used, this will be called every time a user registers or updates his information (including password changing). The function receives two arguments: The user model instance; the input JSON data dict. In case of invalid input (e.g. password too short, email domain not allowed, ...) - you need to raise an exception with a description of why the validation failed.

Extending the User Class

You can extend the built-in User class, that comes prepared with the following properties: is_admin, email, is_email_verified:

from rest_gae.users import User
class MyUser(User):
    """Our own user class"""
    prop1 = ndb.StringProperty(required=True)
    prop2 = ndb.StringProperty()
    
    # This is optional, but if we use a RESTMeta - we must inherit it (and not run over the original properties)
    class RESTMeta(User.RESTMeta):
        excluded_output_properties = User.RESTMeta.excluded_output_properties + ['prop2']