alias=alias,
            title=title,
            description=description,
            gt=gt,
            ge=ge,
            lt=lt,
            le=le,
            min_length=min_length,
            max_length=max_length,
            discriminator=discriminator,
            multiple_of=multiple_of,
            allow_inf_nan=allow_inf_nan,
            max_digits=max_digits,
            decimal_places=decimal_places,

from typing import Annotated

from fastapi import FastAPI, Query

app = FastAPI()


@app.get("/items/")
async def read_items(q: Annotated[str, Query(min_length=3)] = "fixedquery"):
    results = {"items": [{"item_id": "Foo"}, {"item_id": "Bar"}]}
    if q:
        results.update({"q": q})

        serialization_alias=serialization_alias,
        title=title,
        description=description,
        gt=gt,
        ge=ge,
        lt=lt,
        le=le,
        min_length=min_length,
        max_length=max_length,
        pattern=pattern,
        regex=regex,
        discriminator=discriminator,
        strict=strict,
        multiple_of=multiple_of,
        allow_inf_nan=allow_inf_nan,

            " default value together for 'foo'"
        ),
    ):

        @app.get("/")
        async def get3(foo: Annotated[int, Query(min_length=1)] = Depends(dep)):
            pass  # pragma: nocover

    client = TestClient(app)
    response = client.get("/multi-query", params={"foo": "5"})
    assert response.status_code == 200

@app.get("/path/param-minlength/{item_id}")
def get_path_param_min_length(item_id: str = Path(min_length=3)):
    return item_id


@app.get("/path/param-maxlength/{item_id}")
def get_path_param_max_length(item_id: str = Path(max_length=3)):
    return item_id


@app.get("/path/param-min_maxlength/{item_id}")
def get_path_param_min_max_length(item_id: str = Path(max_length=3, min_length=2)):
    return item_id

from typing import Annotated

from fastapi import FastAPI, Query

app = FastAPI()


@app.get("/items/")
async def read_items(q: Annotated[str, Query(min_length=3)]):
    results = {"items": [{"item_id": "Foo"}, {"item_id": "Bar"}]}
    if q:
        results.update({"q": q})

from fastapi import FastAPI, Query

app = FastAPI()


@app.get("/items/")
async def read_items(q: str = Query(min_length=3)):
    results = {"items": [{"item_id": "Foo"}, {"item_id": "Bar"}]}
    if q:
        results.update({"q": q})

Generic validations and metadata:

* `alias`
* `title`
* `description`
* `deprecated`

Validations specific for strings:

* `min_length`
* `max_length`
* `pattern`

Custom validations using `AfterValidator`.

In these examples you saw how to declare validations for `str` values.

## 总结 { #recap }

你可以为参数声明额外的校验和元数据。

通用的校验和元数据：

- `alias`
- `title`
- `description`
- `deprecated`

字符串特有的校验：

- `min_length`
- `max_length`
- `pattern`

也可以使用 `AfterValidator` 进行自定义校验。

在这些示例中，你看到了如何为 `str` 值声明校验。

@app.post("/items/")
async def create_items(items: Annotated[list[int], Field(min_length=1), Body()]):
    return items
```

instead of:

```python
# DO NOT DO THIS
from typing import Annotated

from fastapi import FastAPI
from pydantic import Field, RootModel

app = FastAPI()


class ItemList(RootModel[Annotated[list[int], Field(min_length=1)]]):
    pass


@app.post("/items/")