# Custom Response Classes - File, HTML, Redirect, Streaming, etc.

There are several custom response classes you can use to create an instance and return them directly from your *path operations*.

Read more about it in the [FastAPI docs for Custom Response - HTML, Stream, File, others](https://fastapi.tiangolo.com/advanced/custom-response/).

You can import them directly from `fastapi.responses`:

```python
from fastapi.responses import (
    FileResponse,

/**
 * Wrapper for HTTP servlet requests in web API context.
 * This class extends HttpServletRequestWrapper to provide custom servlet path handling
 * for web API requests.
 */
public class WebApiRequest extends HttpServletRequestWrapper {
    /**
     * The custom servlet path for this web API request.
     */
    protected String servletPath;

    /**

    if (!expression) {
      throw new VerifyException();
    }
  }

  /**
   * Ensures that {@code expression} is {@code true}, throwing a {@code VerifyException} with a
   * custom message otherwise.
   *
   * @param expression a boolean expression
   * @param errorMessageTemplate a template for the exception message should the check fail. The

        "uid": "${DS_PROMETHEUS}"
      },
      "description": "",
      "fieldConfig": {
        "defaults": {
          "color": {
            "mode": "palette-classic"
          },
          "custom": {
            "hideFrom": {
              "legend": false,
              "tooltip": false,
              "viz": false
            }
          },
          "mappings": [
            {

            type[APIRoute],
            Doc(
                """
                Custom route (*path operation*) class to be used by this router.

                Read more about it in the
                [FastAPI docs for Custom Request and APIRoute class](https://fastapi.tiangolo.com/how-to/custom-request-and-route/#custom-apiroute-class-in-a-router).
                """
            ),
        ] = APIRoute,

idated .form-check-input:valid~.valid-tooltip{display:block}.custom-control-input.is-valid~.custom-control-label,.was-validated .custom-control-input:valid~.custom-control-label{color:#28a745}.custom-control-input.is-valid~.custom-control-label::before,.was-validated .custom-control-input:valid~.custom-control-label::before{border-color:#28a745}.custom-control-input.is-valid:checked~.custom-control-label::before,.was-validated .custom-control-input:valid:checked~.custom-control-label::before{bor...

        assertEquals(2, resources.size(), "Should have two resources now");

        // Find the resource with the custom directory
        Resource customResource = resources.stream()
                .filter(r -> r.getDirectory().endsWith("custom"))
                .findFirst()
                .orElseThrow(() -> new AssertionError("Custom resource not found"));

        // Verify targetPath was preserved through conversion chain

class UJSONResponse(JSONResponse):
    """
    JSON response using the high-performance ujson library to serialize data to JSON.

    Read more about it in the
    [FastAPI docs for Custom Response - HTML, Stream, File, others](https://fastapi.tiangolo.com/advanced/custom-response/).
    """

    def render(self, content: Any) -> bytes:
        assert ujson is not None, "ujson must be installed to use UJSONResponse"

def custom_openapi():
    if app.openapi_schema:
        return app.openapi_schema
    openapi_schema = get_openapi(
        title="Custom title",
        version="2.5.0",
        summary="This is a very custom OpenAPI schema",
        description="Here's a longer description of the custom **OpenAPI** schema",
        routes=app.routes,
    )
    openapi_schema["info"]["x-logo"] = {

### Custom Generate Unique ID Function { #custom-generate-unique-id-function }

FastAPI uses a **unique ID** for each *path operation*, which is used for the **operation ID** and also for the names of any needed custom models, for requests or responses.

You can customize that function. It takes an `APIRoute` and outputs a string.