schemas

Schema

A machine-readable [schema] describes what resources are available via the API, what their URLs are, how they are represented and what operations they support.

— Heroku, [JSON Schema for the Heroku Platform API][cite]

API schemas are a useful tool that allow for a range of use cases, including generating reference documentation, or driving dynamic client libraries that can interact with your API.

Django REST Framework provides support for automatic generation of OpenAPI schemas.

Generating an OpenAPI Schema

Install `pyyaml`

You'll need to install pyyaml, so that you can render your generated schema into the commonly used YAML-based OpenAPI format.

pip install pyyaml

Generating a static schema with the `generateschema` management command

If your schema is static, you can use the generateschema management command:

./manage.py generateschema > openapi-schema.yml

Once you've generated a schema in this way you can annotate it with any additional information that cannot be automatically inferred by the schema generator.

You might want to check your API schema into version control and update it with each new release, or serve the API schema from your site's static media.

Generating a dynamic schema with `SchemaView`

If you require a dynamic schema, because foreign key choices depend on database values, for example, you can route a SchemaView that will generate and serve your schema on demand.

To route a SchemaView, use the get_schema_view() helper.

In urls.py:

from rest_framework.schemas import get_schema_view

urlpatterns = [
    # ...
    # Use the `get_schema_view()` helper to add a `SchemaView` to project URLs.
    #   * `title` and `description` parameters are passed to `SchemaGenerator`.
    #   * Provide view name for use with `reverse()`.
    path('openapi', get_schema_view(
        title="Your Project",
        description="API for all things …",
        version="1.0.0"
    ), name='openapi-schema'),
    # ...
]

`get_schema_view()`

The get_schema_view() helper takes the following keyword arguments:

title: May be used to provide a descriptive title for the schema definition.
description: Longer descriptive text.
version: The version of the API.

url: May be used to pass a canonical base URL for the schema.

schema_view = get_schema_view(
    title='Server Monitoring API',
    url='https://www.example.org/api/'
)

urlconf: A string representing the import path to the URL conf that you want to generate an API schema for. This defaults to the value of Django's ROOT_URLCONF setting.
```
schema_view = get_schema_view(
    title='Server Monitoring API',
    url='https://www.example.org/api/',
    urlconf='myproject.urls'
)
```

patterns: List of url patterns to limit the schema introspection to. If you only want the myproject.api urls to be exposed in the schema:

schema_url_patterns = [
    url(r'^api/', include('myproject.api.urls')),
]

schema_view = get_schema_view(
    title='Server Monitoring API',
    url='https://www.example.org/api/',
    patterns=schema_url_patterns,
)

generator_class: May be used to specify a SchemaGenerator subclass to be passed to the SchemaView.
authentication_classes: May be used to specify the list of authentication classes that will apply to the schema endpoint. Defaults to settings.DEFAULT_AUTHENTICATION_CLASSES
permission_classes: May be used to specify the list of permission classes that will apply to the schema endpoint. Defaults to settings.DEFAULT_PERMISSION_CLASSES.
renderer_classes: May be used to pass the set of renderer classes that can be used to render the API root endpoint.

Customizing Schema Generation

You may customize schema generation at the level of the schema as a whole, or on a per-view basis.

In order to customize the top-level schema sublass rest_framework.schemas.openapi.SchemaGenerator and provide it as an argument to the generateschema command or get_schema_view() helper function.

SchemaGenerator

A class that walks a list of routed URL patterns, requests the schema for each view and collates the resulting OpenAPI schema.

Typically you'll instantiate SchemaGenerator with a title argument, like so:

generator = SchemaGenerator(title='Stock Prices API')

Arguments:

title required: The name of the API.
description: Longer descriptive text.
version: The version of the API. Defaults to 0.1.0.
url: The root URL of the API schema. This option is not required unless the schema is included under path prefix.
patterns: A list of URLs to inspect when generating the schema. Defaults to the project's URL conf.
urlconf: A URL conf module name to use when generating the schema. Defaults to settings.ROOT_URLCONF.

get_schema(self, request)

Returns a dictionary that represents the OpenAPI schema:

generator = SchemaGenerator(title='Stock Prices API')
schema = generator.get_schema()

The request argument is optional, and may be used if you want to apply per-user permissions to the resulting schema generation.

This is a good point to override if you want to customize the generated dictionary, for example to add custom specification extensions.

Per-View Customization

By default, view introspection is performed by an AutoSchema instance accessible via the schema attribute on APIView. This provides the appropriate Open API operation object for the view, request method and path:

auto_schema = view.schema
operation = auto_schema.get_operation(...)

In compiling the schema, SchemaGenerator calls view.schema.get_operation() for each view, allowed method, and path.

Note: For basic APIView subclasses, default introspection is essentially limited to the URL kwarg path parameters. For GenericAPIView subclasses, which includes all the provided class based views, AutoSchema will attempt to introspect serializer, pagination and filter fields, as well as provide richer path field descriptions. (The key hooks here are the relevant GenericAPIView attributes and methods: get_serializer, pagination_class, filter_backends and so on.)

In order to customize the operation generation, you should provide an AutoSchema subclass, overriding get_operation() as you need:

    from rest_framework.views import APIView
    from rest_framework.schemas.openapi import AutoSchema

    class CustomSchema(AutoSchema):
        def get_operation(...):
            # Implement custom introspection here (or in other sub-methods)

    class CustomView(APIView):
        """APIView subclass with custom schema introspection."""
        schema = CustomSchema()

This provides complete control over view introspection.

You may disable schema generation for a view by setting schema to None:

class CustomView(APIView):
    ...
    schema = None  # Will not appear in schema

This also applies to extra actions for ViewSets:

class CustomViewSet(viewsets.ModelViewSet):

    @action(detail=True, schema=None)
    def extra_action(self, request, pk=None):
        ...

If you wish to provide a base AutoSchema subclass to be used throughout your project you may adjust settings.DEFAULT_SCHEMA_CLASS appropriately.