FastAPI-XML

Seamless XML support for FastAPI — parse XML request bodies and return XML responses using standard Python dataclasses, with full OpenAPI integration.

pip install fastapi-xml

Built on xsdata for XML serialization, it slots into FastAPI the same way JSON does.

Features

• XML request bodies — replace Body() with XmlBody(), your endpoint receives a populated dataclass
• XML responses — return any dataclass and get back application/xml (or text/xml)
• OpenAPI schema — Swagger UI renders XML examples and schemas automatically
• Zero learning curve — works like FastAPI's JSON, just swap in XmlRoute and XmlBody
• Two media types — XmlAppResponse (application/xml) and XmlTextResponse (text/xml)

Quick Start

from dataclasses import dataclass, field
from fastapi import FastAPI
from fastapi_xml import XmlRoute, XmlAppResponse, XmlBody, add_openapi_extension

@dataclass
class HelloWorld:
    message: str = field(metadata={"type": "Element"})

app = FastAPI(title="FastAPI-XML", default_response_class=XmlAppResponse)
app.router.route_class = XmlRoute
add_openapi_extension(app)

@app.post("/echo", response_model=HelloWorld)
def echo(x: HelloWorld = XmlBody()) -> HelloWorld:
    x.message += " Forever!"
    return x

<!-- Request -->
<HelloWorld><message>Hello</message></HelloWorld>

<!-- Response -->
<HelloWorld><message>Hello Forever!</message></HelloWorld>

How It Works

XmlRoute replaces FastAPI's default APIRoute. When a request arrives with an XML body, the XmlDecoder (wrapping xsdata's XmlParser) deserializes it into your dataclass. On the way out, XmlResponse serializes the return value back to XML via xsdata's XmlSerializer.

Response Types

OpenAPI

Call add_openapi_extension(app) to generate accurate XML schemas in your OpenAPI spec. The Swagger UI at /docs will show XML examples and let you test endpoints directly.

Example

from dataclasses import dataclass, field
from fastapi import FastAPI
from fastapi_xml import XmlRoute, XmlAppResponse, XmlBody


@dataclass
class Item:
    name: str = field(metadata={"type": "Element"})
    price: float = field(metadata={"type": "Element"})

@dataclass
class Order:
    id: str = field(metadata={"type": "Element"})
    items: list[Item] = field(metadata={"type": "Element", "name": "Item"})


app = FastAPI(default_response_class=XmlAppResponse)
app.router.route_class = XmlRoute


@app.post("/order", response_model=Order)
def create_order(order: Order = XmlBody()) -> Order:
    return order


if __name__ == "__main__":
    import uvicorn
    uvicorn.run(app)

API

Requirements

• Python 3.10+
• FastAPI >= 0.113.0
• xsdata >= 22.9

License

MIT