runnableThrowing(exception), DELAY_MS, MILLISECONDS));
    assertThat(e.getCause()).isEqualTo(exception);
  }

  public static <T> Callable<T> callableThrowing(final Exception exception) {
    return new Callable<T>() {
      @Override
      public T call() throws Exception {
        throw exception;
      }
    };
  }

            The parameter is available only for compatibility.
            """
        ),
    ] = ...,
    *,
    default_factory: Annotated[
        Union[Callable[[], Any], None],
        Doc(
            """
            A callable to generate the default value.

            This doesn't affect `Path` parameters as the value is always required.
            The parameter is available only for compatibility.

# Dependencies - `Depends()` and `Security()`

## `Depends()`

Dependencies are handled mainly with the special function `Depends()` that takes a callable.

Here is the reference for it and its parameters.

You can import it directly from `fastapi`:

```python
from fastapi import Depends
```

::: fastapi.Depends

## `Security()`

                    runnableThrowing(exception), DELAY_MS, MILLISECONDS));
    assertThat(e.getCause()).isEqualTo(exception);
  }

  public static <T> Callable<T> callableThrowing(final Exception exception) {
    return new Callable<T>() {
      @Override
      public T call() throws Exception {
        throw exception;
      }
    };
  }

    assertFile(Relay.PREFIX_CLEAN, 20L, metadata.size, "abcdefghijklmnopqrst", metadata)
  }

  /** Returns a callable that reads all of source, closes it, and returns the bytes.  */
  private fun sourceReader(source: Source?): Callable<ByteString> {
    return Callable {
      val buffer = Buffer()
      while (source!!.read(buffer, 16384) != -1L) {
      }
      source.close()

from typing import (
    Any,
    BinaryIO,
    Callable,
    Dict,
    Iterable,
    Optional,
    Type,
    TypeVar,
    cast,
)

from fastapi._compat import (
    PYDANTIC_V2,
    CoreSchema,
    GetJsonSchemaHandler,
    JsonSchemaValue,
    with_info_plain_validator_function,
)
from starlette.datastructures import URL as URL  # noqa: F401
from starlette.datastructures import Address as Address  # noqa: F401

Eine Python-Klasse ist also auch ein **Callable**.

Darum können Sie in **FastAPI** auch eine Python-Klasse als Abhängigkeit verwenden.

Was FastAPI tatsächlich prüft, ist, ob es sich um ein „Callable“ (Funktion, Klasse oder irgendetwas anderes) handelt und ob die Parameter definiert sind.

import time
from typing import Callable

from fastapi import APIRouter, FastAPI, Request, Response
from fastapi.routing import APIRoute


class TimedRoute(APIRoute):
    def get_route_handler(self) -> Callable:
        original_route_handler = super().get_route_handler()

        async def custom_route_handler(request: Request) -> Response:
            before = time.time()
            response: Response = await original_route_handler(request)

import com.google.errorprone.annotations.DoNotMock;
import java.util.Map;
import java.util.concurrent.Callable;
import java.util.concurrent.ConcurrentMap;
import java.util.concurrent.ExecutionException;
import javax.annotation.CheckForNull;

/**
 * A semi-persistent mapping from keys to values. Cache entries are manually added using {@link
 * #get(Object, Callable)} or {@link #put(Object, Object)}, and are stored in the cache until either

        if response_fields:
            self.response_fields: Dict[Union[int, str], ModelField] = response_fields
        else:
            self.response_fields = {}

        assert callable(endpoint), "An endpoint must be a callable"
        self.dependant = get_dependant(path=self.path_format, call=self.endpoint)
        for depends in self.dependencies[::-1]:
            self.dependant.dependencies.insert(
                0,