/// info

`Body` also has all the same extra validation and metadata parameters as `Query`, `Path` and others you will see later.

///

## Embed a single body parameter { #embed-a-single-body-parameter }

Let's say you only have a single `item` body parameter from a Pydantic model `Item`.

By default, **FastAPI** will then expect its body directly.

    public abstract RegularFileProperty getDestinationFile();

    /**
     * The release notes JavaScript to embed in the HTML
     */
    @InputFile
    @PathSensitive(PathSensitivity.NONE)
    public abstract RegularFileProperty getReleaseNotesJavascriptFile();

    /**
     * The release notes CSS to embed in the HTML
     */
    @InputFile
    @PathSensitive(PathSensitivity.NONE)

# =====================================================================================
# Without aliases


@app.post("/required-str", operation_id="required_str")
async def read_required_str(p: Annotated[str, Body(embed=True)]):
    return {"p": p}


class BodyModelRequiredStr(BaseModel):
    p: str


@app.post("/model-required-str", operation_id="model_required_str")
async def read_model_required_str(p: BodyModelRequiredStr):

    )
    price: float = Field(gt=0, description="The price must be greater than zero")
    tax: float | None = None


@app.put("/items/{item_id}")
async def update_item(item_id: int, item: Item = Body(embed=True)):
    results = {"item_id": item_id, "item": item}

# Without aliases


@app.post("/required-list-str", operation_id="required_list_str")
async def read_required_list_str(p: Annotated[list[str], Body(embed=True)]):
    return {"p": p}


class BodyModelRequiredListStr(BaseModel):
    p: list[str]


@app.post("/model-required-list-str", operation_id="model_required_list_str")

# =====================================================================================
# Without aliases


@app.post("/optional-str", operation_id="optional_str")
async def read_optional_str(p: Annotated[str | None, Body(embed=True)] = None):
    return {"p": p}


class BodyModelOptionalStr(BaseModel):
    p: str | None = None


@app.post("/model-optional-str", operation_id="model_optional_str")

# Without aliases


@app.post("/optional-list-str", operation_id="optional_list_str")
async def read_optional_list_str(
    p: Annotated[list[str] | None, Body(embed=True)] = None,
):
    return {"p": p}


class BodyModelOptionalListStr(BaseModel):
    p: list[str] | None = None


@app.post("/model-optional-list-str", operation_id="model_optional_list_str")

`Body` 也具有與 `Query`、`Path` 以及之後你會看到的其他工具相同的額外驗證與中繼資料參數。

///

## 嵌入單一 Body 參數 { #embed-a-single-body-parameter }

假設你只有一個來自 Pydantic 模型 `Item` 的單一 `item` Body 參數。

預設情況下，**FastAPI** 會直接期望該模型的內容作為請求主體。

但如果你想讓它像宣告多個 Body 參數時那樣，期望一個帶有 `item` 鍵、其內含模型內容的 JSON，你可以使用 `Body` 的特殊參數 `embed`：

```Python
item: Item = Body(embed=True)
```

如下：

class Item(BaseModel):
    name: str
    description: str | None = None
    price: float
    tax: float | None = None


@app.put("/items/{item_id}")
async def update_item(item_id: int, item: Item = Body(embed=True)):
    results = {"item_id": item_id, "item": item}

class Item(BaseModel):
    name: str
    description: str | None = None
    size: float


app = FastAPI()


@app.post("/items/")
async def create_item(item: Annotated[Item, Body(embed=True)]) -> Item: