Aiohttp pydantic - Aiohttp View to validate and parse request

Aiohttp pydantic is an aiohttp view to easily parse and validate request. You define using the function annotations what your methods for handling HTTP verbs expects and Aiohttp pydantic parses the HTTP request for you, validates the data, and injects that you want as parameters.

Features:

• Query string, request body, URL path and HTTP headers validation.
• Authentication and authorization with multiple security schemes
• Automatic OpenAPI Specification generation with security documentation
• File Upload: Handle file uploads with multipart/form-data validation

What's New in 3.0.0

Comprehensive Security System

Version 3.0.0 introduces a powerful authentication and authorization framework:

• Multiple authentication schemes: JWT, API Keys, OAuth2, OpenID Connect
• Flexible authorization: Design your own permission rules (strings, enums, custom objects)
• Composable rules: Combine authentication methods with | (OR) and & (AND) operators
• Context-aware permissions: Make authorization decisions based on the requested resource
• Automatic OpenAPI documentation: Security schemes are automatically included in the spec

See the Authentication and Authorization section for complete documentation.

Breaking Changes

• Dropped support for Python 3.10 and 3.11
• Requires aiohttp >= 3.10
• Removed deprecated features (see changelog for details)

How to install

$ pip install aiohttp_pydantic

Example:

from typing import Optional

from aiohttp import web
from aiohttp_pydantic import PydanticView
from pydantic import BaseModel

# Use pydantic BaseModel to validate request body
class ArticleModel(BaseModel):
    name: str
    nb_page: Optional[int]


# Create your PydanticView and add annotations.
class ArticleView(PydanticView):

    async def post(self, article: ArticleModel):
        return web.json_response({'name': article.name,
                                  'number_of_page': article.nb_page})

    async def get(self, with_comments: bool=False):
        return web.json_response({'with_comments': with_comments})


app = web.Application()
app.router.add_view('/article', ArticleView)
web.run_app(app)

$ curl -X GET http://127.0.0.1:8080/article?with_comments=a
[
  {
    "in": "query string",
    "loc": [
      "with_comments"
    ],
    "msg": "Input should be a valid boolean, unable to interpret input",
    "input": "a",
    "type": "bool_parsing"
  }
]

$ curl -X GET http://127.0.0.1:8080/article?with_comments=yes
{"with_comments": true}

$ curl -H "Content-Type: application/json" -X POST http://127.0.0.1:8080/article --data '{}'
[
  {
    "in": "body",
    "loc": [
      "name"
    ],
    "msg": "Field required",
    "input": {},
    "type": "missing"
  },
  {
    "in": "body",
    "loc": [
      "nb_page"
    ],
    "msg": "Field required",
    "input": {},
    "type": "missing"
  }
]

$ curl -H "Content-Type: application/json" -X POST http://127.0.0.1:8080/article --data '{"name": "toto", "nb_page": "3"}'
{"name": "toto", "number_of_page": 3}

Example using view function handler

from typing import Optional

from aiohttp import web
from aiohttp_pydantic.decorator import inject_params
from pydantic import BaseModel


# Use pydantic BaseModel to validate request body
class ArticleModel(BaseModel):
    name: str
    nb_page: Optional[int]


# Create your function decorated by 'inject_params' and add annotations.
@inject_params
async def post(article: ArticleModel):
    return web.json_response({'name': article.name,
                              'number_of_page': article.nb_page})


# If you need request
@inject_params.and_request
async def get(request, with_comments: bool = False):
    request.app["logger"]("OK")
    return web.json_response({'with_comments': with_comments})


app = web.Application()
app["logger"] = print
app.router.add_post('/article', post)
app.router.add_get('/article', get)
web.run_app(app)

API:

Inject Path Parameters

To declare a path parameter, you must declare your argument as a positional-only parameters:

Example:

class AccountView(PydanticView):
    async def get(self, customer_id: str, account_id: str, /):
        ...

app = web.Application()
app.router.add_get('/customers/{customer_id}/accounts/{account_id}', AccountView)

Inject Query String Parameters

To declare a query parameter, you must declare your argument as a simple argument:

class AccountView(PydanticView):
    async def get(self, customer_id: Optional[str] = None):
        ...

app = web.Application()
app.router.add_get('/customers', AccountView)

A query string parameter is generally optional and we do not want to force the user to set it in the URL. It's recommended to define a default value. It's possible to get a multiple value for the same parameter using the List type

from typing import List
from pydantic import Field

class AccountView(PydanticView):
    async def get(self, tags: List[str] = Field(default_factory=list)):
        ...

app = web.Application()
app.router.add_get('/customers', AccountView)

Inject Request Body

To declare a body parameter, you must declare your argument as a simple argument annotated with pydantic Model.

class Customer(BaseModel):
    first_name: str
    last_name: str

class CustomerView(PydanticView):
    async def post(self, customer: Customer):
        ...

app = web.Application()
app.router.add_view('/customers', CustomerView)

Inject HTTP headers

To declare a HTTP headers parameter, you must declare your argument as a keyword-only argument.

class CustomerView(PydanticView):
    async def get(self, *, authorization: str, expire_at: datetime):
        ...

app = web.Application()
app.router.add_view('/customers', CustomerView)

File Upload

You can receive files in addition to Pydantic data in your views. Here’s an example of how to use it: Usage Example

Suppose you want to create an API that accepts a book (with a title and a number of pages) as well as two files representing the pages of the book. Here’s how you can do it:

from aiohttp import web
from aiohttp_pydantic import PydanticView
from aiohttp_pydantic.uploaded_file import UploadedFile
from pydantic import BaseModel

class BookModel(BaseModel):
    title: str
    nb_page: int

class BookAndUploadFileView(PydanticView):
    async def post(self, book: BookModel, page_1: UploadedFile, page_2: UploadedFile):
        content_1 = (await page_1.read()).decode("utf-8")
        content_2 = (await page_2.read()).decode("utf-8")
        return web.json_response(
            {"book": book.model_dump(), "content_1": content_1, "content_2": content_2},
            status=201,
        )

Implementation Details

Files are represented by instances of UploadedFile, which wrap an aiohttp.BodyPartReader. UploadedFile exposes the read() and read_chunk() methods, allowing you to read the content of uploaded files asynchronously. You can use read() to get the complete content or read_chunk() to read chunks of data at a time.

Constraints to Consider

1 - Argument Order: If you use both Pydantic models and UploadedFile, you must always define BaseModel type arguments before UploadedFile type arguments. This ensures proper processing of the data.

2 - File Reading Order: UploadedFile instances must be read in the order they are declared in the method. Since files are not pre-loaded in memory or on disk, it is important to respect this order. If the reading order is not respected, a MultipartReadingError is raised.

Add route to generate Open Api Specification (OAS)

aiohttp_pydantic provides a sub-application to serve a route to generate Open Api Specification reading annotation in your PydanticView. Use aiohttp_pydantic.oas.setup() to add the sub-application

from aiohttp import web
from aiohttp_pydantic import oas


app = web.Application()
oas.setup(app)

By default, the route to display the Open Api Specification is /oas but you can change it using url_prefix parameter

oas.setup(app, url_prefix='/spec-api')

If you want generate the Open Api Specification from specific aiohttp sub-applications. on the same route, you must use apps_to_expose parameter.

from aiohttp import web
from aiohttp_pydantic import oas

app = web.Application()
sub_app_1 = web.Application()
sub_app_2 = web.Application()

oas.setup(app, apps_to_expose=[sub_app_1, sub_app_2])

You can change the title or the version of the generated open api specification using title_spec and version_spec parameters:

oas.setup(app, title_spec="My application", version_spec="1.2.3")

Add annotation to define response content

The module aiohttp_pydantic.oas.typing provides class to annotate a response content.

For example r200[List[Pet]] means the server responses with the status code 200 and the response content is a List of Pet where Pet will be defined using a pydantic.BaseModel

The docstring of methods will be parsed to fill the descriptions in the Open Api Specification.

from aiohttp_pydantic import PydanticView
from aiohttp_pydantic.oas.typing import r200, r201, r204, r404


class Pet(BaseModel):
    id: int
    name: str


class Error(BaseModel):
    error: str


class PetCollectionView(PydanticView):
    async def get(self) -> r200[List[Pet]]:
        """
        Find all pets

        Tags: pet
        """
        pets = self.request.app["model"].list_pets()
        return web.json_response([pet.dict() for pet in pets])

    async def post(self, pet: Pet) -> r201[Pet]:
        """
        Add a new pet to the store

        Tags: pet
        Status Codes:
            201: The pet is created
        """
        self.request.app["model"].add_pet(pet)
        return web.json_response(pet.dict())


class PetItemView(PydanticView):
    async def get(self, id: int, /) -> Union[r200[Pet], r404[Error]]:
        """
        Find a pet by ID

        Tags: pet
        Status Codes:
            200: Successful operation
            404: Pet not found
        """
        pet = self.request.app["model"].find_pet(id)
        return web.json_response(pet.dict())

    async def put(self, id: int, /, pet: Pet) -> r200[Pet]:
        """
        Update an existing pet

        Tags: pet
        Status Codes:
            200: successful operation
        """
        self.request.app["model"].update_pet(id, pet)
        return web.json_response(pet.dict())

    async def delete(self, id: int, /) -> r204:
        self.request.app["model"].remove_pet(id)
        return web.Response(status=204)

Patching JSON Schema

You can define a function that modifies a Pydantic-generated schema in-place:

def pydantic_schema_to_oas_3_0(schema: dict) -> None:
    """
    Modify the JSON schema in place.

    This function receives a Pydantic-generated JSON schema as a dictionary,
    and can adjust or enhance it before it is used in the OpenAPI specification.
    """

Once defined, you can register it:

oas.pydantic_schema_to_oas.add_or_replace_translater(
    "3.0.0", pydantic_schema_to_oas_3_0
)

Group parameters

If your method has lot of parameters you can group them together inside one or several Groups.

from aiohttp_pydantic.injectors import Group

class Pagination(Group):
    page_num: int = 1
    page_size: int = 15


class ArticleView(PydanticView):

    async def get(self, page: Pagination):
        articles = Article.get(page.page_num, page.page_size)
        ...

The parameters page_num and page_size are expected in the query string, and set inside a Pagination object passed as page parameter.

The code above is equivalent to:

class ArticleView(PydanticView):

    async def get(self, page_num: int = 1, page_size: int = 15):
        articles = Article.get(page_num, page_size)
        ...

You can add methods or properties to your Group.

class Pagination(Group):
    page_num: int = 1
    page_size: int = 15

    @property
    def num(self):
        return self.page_num

    @property
    def size(self):
        return self.page_size

    def slice(self):
        return slice(self.num, self.size)


class ArticleView(PydanticView):

    async def get(self, page: Pagination):
        articles = Article.get(page.num, page.size)
        ...

Custom Validation error

You can redefine the on_validation_error hook in your PydanticView

class PetView(PydanticView):

    async def on_validation_error(self,
                                  exception: ValidationError,
                                  context: str):
        errors = exception.errors()
        for error in errors:
            error["in"] = context  # context is "body", "headers", "path" or "query string"
            error["custom"] = "your custom field ..."
        return json_response(data=errors, status=400)

If you use function based view:

async def custom_error(exception: ValidationError,
                       context: str):
    errors = exception.errors()
    for error in errors:
        error["in"] = context  # context is "body", "headers", "path" or "query string"
        error["custom"] = "your custom field ..."
    return json_response(data=errors, status=400)


@inject_params(on_validation_error=custom_error)
async def get(with_comments: bool = False):
    ...

@inject_params.and_request(on_validation_error=custom_error)
async def get(request, with_comments: bool = False):
    ...

A tip to use the same error handling on each view

inject_params = inject_params(on_validation_error=custom_error)


@inject_params
async def post(article: ArticleModel):
    return web.json_response({'name': article.name,
                              'number_of_page': article.nb_page})


@inject_params.and_request
async def get(request, with_comments: bool = False):
    return web.json_response({'with_comments': with_comments})

Authentication and Authorization

aiohttp_pydantic provides a comprehensive security system for handling authentication and authorization in your API. Security schemes are automatically included in the OpenAPI specification, and the @auth decorator adds security requirements to endpoint documentation.

You define security schemes, register them with your application, and then use the @auth decorator to protect your endpoints.

Setup Security Schemes

A security scheme consists of two main responsibilities:

1. Authentication (authenticate method): Verify the user's identity from the request
2. Authorization (permits method): Check if the authenticated user has permission for a specific action

Define your security scheme by inheriting from one of the base classes and implementing the authenticate and permits methods.

The rule parameter passed to permits() is fully application-defined. The framework does not impose any specific type or structure. You are free to design your own authorization model.

For example, rule can be:

• A simple str (e.g., "admin", "owner")
• An Enum for stronger typing
• A complex object representing a small authorization DSL
• Any other Python object

The value passed to @auth(USER_AUTH.rule(...)) will be forwarded as-is to permits().

from aiohttp import web
from aiohttp_pydantic.security.auth_scheme import HTTPSecurityScheme
from aiohttp_pydantic.security.exceptions import AuthenticationError
import jwt
from jwt import PyJWTError

class JWTAuth(HTTPSecurityScheme):
    """
    JWT Bearer token authentication
    """
    scheme = "Bearer"
    bearer_format = "JWT"

    def __init__(self, jwt_secret):
        self._jwt_secret = jwt_secret

    async def authenticate(self, request: web.Request) -> dict:
        """
        Verify the JWT token and return the payload.

        Raises:
            AuthenticationError: If the token is invalid or expired
        """
        token = self.extract_credentials(request)  # Extracts "Bearer <token>"
        try:
            payload = jwt.decode(token, self._jwt_secret, algorithms="HS256")
            return payload
        except PyJWTError as error:
            raise AuthenticationError(str(error)) from error

    async def permits(
        self,
        request: web.Request,
        identity: dict,  # The payload returned by authenticate()
        rule: str,
        context: dict
    ) -> bool:
        """
        Check if the authenticated user has the required permission.

        Args:
            identity: The authenticated user data (JWT payload)
            rule: The permission rule to check (e.g., "user", "admin")
            context: Validated handler parameters (e.g., {"id": 123} for /pets/{id})
        """
        if rule == "admin":
            return identity.get("admin", False)
        return True

# Create a reference to use in decorators
USER_AUTH = JWTAuth.ref("USER_AUTH")

Then register your security scheme with the application:

from aiohttp import web
from aiohttp_pydantic import oas, security

app = web.Application()

# Setup OpenAPI documentation
oas.setup(app, title_spec="My API", version_spec="1.0.0")

# Register security schemes
security.setup(
    app,
    schemes={USER_AUTH: JWTAuth(jwt_secret="your-secret-key")}
)

Protect Endpoints

Use the @auth decorator to require authentication and authorization on your endpoints:

from aiohttp_pydantic import PydanticView
from aiohttp_pydantic.decorator import auth
from pydantic import BaseModel

class Pet(BaseModel):
    name: str
    age: int

class PetCollectionView(PydanticView):

    # Public endpoint - no authentication required
    async def get(self) -> List[Pet]:
        """List all pets"""
        pets = self.request.app["model"].list_pets()
        return web.json_response([pet.dict() for pet in pets])

    # Protected endpoint - requires authentication with "write" permission
    @auth(USER_AUTH.rule("write"))
    async def post(self, pet: Pet) -> Pet:
        """
        Create a new pet

        Requires: Valid JWT token with "write" permission
        """
        new_pet = self.request.app["model"].add_pet(pet)
        return web.json_response(new_pet.dict())

class PetItemView(PydanticView):

    # Protected endpoint - requires admin permission
    @auth(USER_AUTH.rule("admin"))
    async def delete(self, id: int, /) -> None:
        """
        Delete a pet

        Requires: Valid JWT token with "admin" permission
        """
        self.request.app["model"].remove_pet(id)
        return web.Response(status=204)

Available Security Scheme Types

aiohttp_pydantic provides several built-in security scheme types:

HTTPSecurityScheme - HTTP authentication (Basic, Bearer, etc.)

from aiohttp_pydantic.security.auth_scheme import HTTPSecurityScheme

class BearerAuth(HTTPSecurityScheme):
    scheme = "Bearer"
    bearer_format = "JWT"  # Optional hint for documentation

APIKeySecurityScheme - API key in header, query, or cookie

from aiohttp_pydantic.security.auth_scheme import APIKeySecurityScheme

class APIKeyAuth(APIKeySecurityScheme):
    parameter_name = "X-API-Key"  # Header name
    location = "header"  # Can be "header", "query", or "cookie"

OAuth2SecurityScheme - OAuth 2.0 flows

from aiohttp_pydantic.security.auth_scheme import OAuth2SecurityScheme

class OAuth2Auth(OAuth2SecurityScheme):
    def __init__(self):
        flows = {
            "authorizationCode": {
                "authorizationUrl": "https://example.com/oauth/authorize",
                "tokenUrl": "https://example.com/oauth/token",
                "scopes": {
                    "read": "Read access",
                    "write": "Write access"
                }
            }
        }
        super().__init__(flows)

OpenIdConnectSecurityScheme - OpenID Connect Discovery

from aiohttp_pydantic.security.auth_scheme import OpenIdConnectSecurityScheme

class OpenIDAuth(OpenIdConnectSecurityScheme):
    def __init__(self):
        super().__init__("https://example.com/.well-known/openid-configuration")

Combining Authentication Rules

You can combine multiple authentication schemes using | (OR) and & (AND) operators:

OR operator - User can authenticate with either scheme:

# Accept either JWT token OR API key
@auth(USER_AUTH.rule("read") | API_KEY_AUTH.rule(1))
async def get(self, id: int, /):
    """Endpoint accessible with JWT or API key"""
    ...

AND operator - User must authenticate with both schemes:

# Requires BOTH JWT token AND API key
@auth(USER_AUTH.rule("read") & API_KEY_AUTH.rule(1))
async def get(self):
    """Endpoint requiring both JWT and API key"""
    ...

Complex combinations:

# (JWT with admin) OR (API key level 3 AND machine certificate)
@auth((USER_AUTH.rule("admin") | API_KEY_AUTH.rule(3)) & CERT_AUTH.rule("machine"))
async def get(self):
    """Complex authentication requirements"""
    ...

Context-Based Authorization

The context parameter in permits() receives validated handler parameters, allowing you to implement resource-based permissions:

class JWTAuth(HTTPSecurityScheme):
    async def permits(self, request, identity, rule, context):
        if rule == "owner":
            # context contains validated path parameters
            pet_id = context["id"]  # From /pets/{id}
            pet = request.app["model"].find_pet(pet_id)

            # Check if user is the owner
            user_id = identity.get("sub")
            return pet.owner_id == int(user_id)

        return True

class PetItemView(PydanticView):
    @auth(USER_AUTH.rule("owner"))
    async def put(self, id: int, /, pet: Pet):
        """
        Update a pet

        Only the pet owner can update it
        """
        self.request.app["model"].update_pet(id, pet)
        return web.json_response(pet.dict())

Error Handling

The security middleware automatically converts authentication and authorization errors into appropriate HTTP responses:

• AuthenticationError → HTTP 401 Unauthorized
• AuthorizationError → HTTP 403 Forbidden

from aiohttp_pydantic.security.exceptions import AuthenticationError

async def authenticate(self, request):
    token = self.extract_credentials(request)
    if not self.is_valid(token):
        raise AuthenticationError("Invalid token")
    return self.decode_token(token)

Using with Function-Based Handlers

The @auth decorator also works with function-based handlers:

from aiohttp_pydantic.decorator import inject_params, auth

@inject_params.and_request.with_auth(USER_AUTH.rule("read"))
async def get_articles(request, page: int = 1):
    """
    List articles

    Requires: Valid JWT token with "read" permission
    """
    articles = request.app["model"].list_articles(page)
    return web.json_response(articles)

app = web.Application()
app.router.add_get('/articles', get_articles)
security.setup(app, {USER_AUTH: JWTAuth(jwt_secret="secret")})

OpenAPI Documentation

Security schemes are automatically included in the OpenAPI specification. The @auth decorator adds security requirements to endpoint documentation:

# The generated OpenAPI spec will include:
{
  "paths": {
    "/pets": {
      "post": {
        "security": [
          {"USER_AUTH": ["write"]}
        ]
      }
    }
  },
  "components": {
    "securitySchemes": {
      "USER_AUTH": {
        "type": "http",
        "scheme": "bearer",
        "bearerFormat": "JWT"
      }
    }
  }
}

Demo

Have a look at demo for a complete example

git clone https://github.com/Maillol/aiohttp-pydantic.git
cd aiohttp-pydantic
pip install .
python -m demo

Go to http://127.0.0.1:8080/oas

You can generate the OAS in a json or yaml file using the aiohttp_pydantic.oas command:

python -m aiohttp_pydantic.oas demo.main

$ python3 -m aiohttp_pydantic.oas  --help
usage: __main__.py [-h] [-b FILE] [-o FILE] [-f FORMAT] [APP [APP ...]]

Generate Open API Specification

positional arguments:
  APP                   The name of the module containing the asyncio.web.Application. By default the variable named
                        'app' is loaded but you can define an other variable name ending the name of module with :
                        characters and the name of variable. Example: my_package.my_module:my_app If your
                        asyncio.web.Application is returned by a function, you can use the syntax:
                        my_package.my_module:my_app()

optional arguments:
  -h, --help            show this help message and exit
  -b FILE, --base-oas-file FILE
                        A file that will be used as base to generate OAS
  -o FILE, --output FILE
                        File to write the output
  -f FORMAT, --format FORMAT
                        The output format, can be 'json' or 'yaml' (default is json)