"type": "prometheus",
        "uid": "${DS_PROMETHEUS}"
      },
      "fieldConfig": {
        "defaults": {
          "color": {
            "mode": "palette-classic"
          },
          "custom": {
            "axisBorderShow": false,
            "axisCenteredZero": false,
            "axisColorMode": "text",
            "axisLabel": "",
            "axisPlacement": "auto",
            "barAlignment": 0,

## Install custom exception handlers { #install-custom-exception-handlers }

You can add custom exception handlers with <a href="https://www.starlette.dev/exceptions/" class="external-link" target="_blank">the same exception utilities from Starlette</a>.

Let's say you have a custom exception `UnicornException` that you (or a library you use) might `raise`.

And you want to handle this exception globally with FastAPI.

        }
    }

    @Nested
    @DisplayName("getMimeType with custom default")
    class GetMimeTypeWithDefault {

        @Test
        @DisplayName("Should return custom default for unknown extensions")
        void testCustomDefaultForUnknown() throws IOException {
            String customDefault = "application/custom";
            assertEquals(customDefault, mimeMap.getMimeType("unknownext", customDefault));

        "type": "prometheus",
        "uid": "${DS_PROMETHEUS}"
      },
      "fieldConfig": {
        "defaults": {
          "color": {
            "mode": "palette-classic"
          },
          "custom": {
            "axisBorderShow": false,
            "axisCenteredZero": false,
            "axisColorMode": "text",
            "axisLabel": "",
            "axisPlacement": "auto",
            "barAlignment": 0,

{* ../../docs_src/additional_responses/tutorial003_py39.py hl[20:31] *}

It will all be combined and included in your OpenAPI, and shown in the API docs:

<img src="/img/tutorial/additional-responses/image01.png">

## Combine predefined responses and custom ones { #combine-predefined-responses-and-custom-ones }

///

## Returning a custom `Response` { #returning-a-custom-response }

The example above shows all the parts you need, but it's not very useful yet, as you could have just returned the `item` directly, and **FastAPI** would put it in a `JSONResponse` for you, converting it to a `dict`, etc. All that by default.

Now, let's see how you could use that to return a custom response.

        "type": "prometheus",
        "uid": "${DS_PROMETHEUS}"
      },
      "fieldConfig": {
        "defaults": {
          "color": {
            "mode": "palette-classic"
          },
          "custom": {
            "axisBorderShow": false,
            "axisCenteredZero": false,
            "axisColorMode": "text",
            "axisLabel": "",
            "axisPlacement": "auto",
            "barAlignment": 0,

        "uid": "${DS_PROMETHEUS}"
      },
      "description": "",
      "fieldConfig": {
        "defaults": {
          "color": {
            "mode": "palette-classic"
          },
          "custom": {
            "axisBorderShow": false,
            "axisCenteredZero": false,
            "axisColorMode": "text",
            "axisLabel": "",
            "axisPlacement": "auto",
            "barAlignment": 0,

    }

    @Test
    @DisplayName("Test custom implementation with signing not enforced")
    void testCustomImplementationSigningNotEnforced() {
        // Given
        SmbNegotiationRequest request = new TestSmbNegotiationRequest(false);

        // When
        boolean result = request.isSigningEnforced();

        // Then
        assertFalse(result, "Custom implementation should return false when initialized with false");

    - topic_repos: ../en/data/topic_repos.yml
  redirects:
    redirect_maps:
      deployment/deta.md: deployment/cloud.md
      advanced/graphql.md: how-to/graphql.md
      advanced/custom-request-and-route.md: how-to/custom-request-and-route.md
      advanced/conditional-openapi.md: how-to/conditional-openapi.md
      advanced/extending-openapi.md: how-to/extending-openapi.md