And that function takes parameters in the same way that *path operation functions* do.

/// tip

You'll see what other "things", apart from functions, can be used as dependencies in the next chapter.

///

Whenever a new request arrives, **FastAPI** will take care of:

* Calling your dependency ("dependable") function with the correct parameters.

* It takes each **request** that comes to your application.
* It can then do something to that **request** or run any needed code.
* Then it passes the **request** to be processed by the rest of the application (by some *path operation*).
* It then takes the **response** generated by the application (by some *path operation*).

      if (iterations >= maxIterations) {
        @SuppressWarnings("nullness") // safe because we pass sort() a range that contains real Ts
        T[] castBuffer = (T[]) buffer;
        // We've already taken O(k log k), let's make sure we don't take longer than O(k log k).
        sort(castBuffer, left, right + 1, comparator);
        break;
      }
    }
    bufferSize = k;

### `HTMLResponse` { #htmlresponse }

Takes some text or bytes and returns an HTML response, as you read above.

### `PlainTextResponse` { #plaintextresponse }

Takes some text or bytes and returns a plain text response.

{* ../../docs_src/custom_response/tutorial005_py39.py hl[2,7,9] *}

### `JSONResponse` { #jsonresponse }

Takes some data and returns an `application/json` encoded response.

 * as a ByteArrayInputStream.
 * </p>
 *
 * <p>
 * The transform method takes a ResponseData object, checks if it has a response body,
 * and then reads the body into a byte array. This byte array is then set as the data
 * in the ResultData object.
 * </p>
 *
 * <p>
 * The getData method takes an AccessResultData object, checks if the transformer name matches,

   *       maxPermits is equal to warmupPeriod.
   *   <li>When _used_, the time it takes, as explained in the introductory class note, is equal to
   *       the integral of our function, between X permits and X-K permits, assuming we want to
   *       spend K saved permits.
   * </ol>
   *

import org.apache.maven.artifact.metadata.ArtifactMetadataSource;
import org.apache.maven.artifact.repository.ArtifactRepository;
import org.apache.maven.artifact.resolver.filter.ArtifactFilter;

/**
 * Artifact collector - takes a set of original artifacts and resolves the best versions to use
 * along with their metadata. No artifacts are downloaded.
 */
@Deprecated

			xForwardedFor: []string{"8.8.8.8"},
			xRealIP:       []string{"1.1.1.1"},
		},
	}
	// When X-Forwarded-For and X-Real-IP headers are both present, X-Forwarded-For takes precedence.
	res := GetSourceIP(req)
	if res != "8.8.8.8" {
		t.Errorf("wrong header, xff takes precedence: got %s, want: 8.8.8.8", res)
	}

	// When explicitly disabled, the XFF header is ignored and X-Real-IP is used.
	enableXFFHeader = false
	defer func() {

   *     .collect(least(2, comparingInt(String::length)))
   * // returns {"foo", "quux"}
   * }
   *
   * <p>This {@code Collector} uses O(k) memory and takes expected time O(n) (worst-case O(n log
   * k)), as opposed to e.g. {@code Stream.sorted(comparator).limit(k)}, which currently takes O(n
   * log n) time and O(n) space.
   *
   * @throws IllegalArgumentException if {@code k < 0}
   * @since 22.0
   */

# `HTTPConnection` class

When you want to define dependencies that should be compatible with both HTTP and WebSockets, you can define a parameter that takes an `HTTPConnection` instead of a `Request` or a `WebSocket`.

You can import it from `fastapi.requests`:

```python
from fastapi.requests import HTTPConnection
```