FastAPI Response(四) 高级定制的Response

作者：麦克煎蛋   出处：https://www.cnblogs.com/mazhiyong/ 转载请保留这段声明，谢谢！

我们可以更灵活的定制返回结果。(这部分是相对高级的内容，如果你是初次接触FastAPI那么可以忽略)

参数responses

我们可以传递给路径操作装饰器一个参数responses，他接收一个字典数据，键值是不同的HTTP状态码，内容是不同情况下的返回内容(字典格式)。

如果返回内容包含键值model，那么它的作用与response_model相同，指向的内容是Pydantic模型。

如下示例，当返回状态码是404的时候，对应的Pydantic模型是Message：

from fastapi import FastAPI
from fastapi.responses import JSONResponse
from pydantic import BaseModel


class Item(BaseModel):
    id: str
    value: str


class Message(BaseModel):
    message: str


app = FastAPI()


@app.get("/items/{item_id}", response_model=Item, responses={404: {"model": Message}})
async def read_item(item_id: str):
    if item_id == "foo":
        return {"id": "foo", "value": "there goes my hero"}
    else:
        return JSONResponse(status_code=404, content={"message": "Item not found"})

在上面的示例中，正常情况下返回的数据模型是Item，404的时候返回的数据模型是Message。

不同的media type

参数responses也支持不同的media type。

from typing import Optional

from fastapi import FastAPI
from fastapi.responses import FileResponse
from pydantic import BaseModel


class Item(BaseModel):
    id: str
    value: str


app = FastAPI()


@app.get(
    "/items/{item_id}",
    response_model=Item,
    responses={
        200: {
            "content": {"image/png": {}},
            "description": "Return the JSON item or an image.",
        }
    },
)
async def read_item(item_id: str, img: Optional[bool] = None):
    if img:
        return FileResponse("image.png", media_type="image/png")
    else:
        return {"id": "foo", "value": "there goes my hero"}

如上所示，默认的media type是application/json，同时还支持image/png。

返回信息的组合格式

我们可以合并不同的组合信息，其中可以包含response_model, status_code, 以及 responses等参数。

from fastapi import FastAPI
from fastapi.responses import JSONResponse
from pydantic import BaseModel


class Item(BaseModel):
    id: str
    value: str


class Message(BaseModel):
    message: str


app = FastAPI()


@app.get(
    "/items/{item_id}",
    response_model=Item,
    responses={
        404: {"model": Message, "description": "The item was not found"},
        200: {
            "description": "Item requested by ID",
            "content": {
                "application/json": {
                    "example": {"id": "bar", "value": "The bar tenders"}
                }
            },
        },
    },
)
async def read_item(item_id: str):
    if item_id == "foo":
        return {"id": "foo", "value": "there goes my hero"}
    else:
        return JSONResponse(status_code=404, content={"message": "Item not found"})

合并预定义responses与自定义responses

from typing import Optional

from fastapi import FastAPI
from fastapi.responses import FileResponse
from pydantic import BaseModel


class Item(BaseModel):
    id: str
    value: str


responses = {
    404: {"description": "Item not found"},
    302: {"description": "The item was moved"},
    403: {"description": "Not enough privileges"},
}


app = FastAPI()


@app.get(
    "/items/{item_id}",
    response_model=Item,
    responses={**responses, 200: {"content": {"image/png": {}}}},
)
async def read_item(item_id: str, img: Optional[bool] = None):
    if img:
        return FileResponse("image.png", media_type="image/png")
    else:
        return {"id": "foo", "value": "there goes my hero"}