## Custom response class { #custom-response-class }

You can create your own custom response class, inheriting from `Response` and using it.

For example, let's say that you want to use <a href="https://github.com/ijl/orjson" class="external-link" target="_blank">`orjson`</a>, but with some custom settings not used in the included `ORJSONResponse` class.

* Automatically logging all request bodies.

## Handling custom request body encodings { #handling-custom-request-body-encodings }

Let's see how to make use of a custom `Request` subclass to decompress gzip requests.

And an `APIRoute` subclass to use that custom request class.

### Create a custom `GzipRequest` class { #create-a-custom-gziprequest-class }

/// tip

The same as when using a custom CDN, the first step is to disable the automatic docs, as those use the CDN by default.

To disable them, set their URLs to `None` when creating your `FastAPI` app:

{* ../../docs_src/custom_docs_ui/tutorial002.py hl[9] *}

### Include the custom docs for static files { #include-the-custom-docs-for-static-files }

        System.setProperty("custom.prop.one", "value1");
        System.setProperty("custom.prop.two", "value2");
        System.setProperty("other.property", "value3");

        // Test with regex pattern
        execJob.testAddFessCustomSystemProperties(cmdList, "custom\\.prop\\..*");

        assertEquals(2, cmdList.size());
        assertTrue(cmdList.contains("-Dcustom.prop.one=value1"));

        assertEquals("Custom minKey should match", "custom.min", customAnnotation.minKey());
        assertEquals("Custom maxKey should match", "custom.max", customAnnotation.maxKey());
        assertEquals("Annotation type should be CustomSize", CustomSize.class, customAnnotation.annotationType());
    }

    // Test annotation with empty keys

///

## Custom Headers { #custom-headers }

Keep in mind that custom proprietary headers can be added <a href="https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers" class="external-link" target="_blank">using the 'X-' prefix</a>.

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

You can add custom exception handlers with <a href="https://www.starlette.io/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.

{* ../../docs_src/additional_responses/tutorial003.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 }

        // Test getMailReturnPath
        assertEquals("root@localhost", fessEnv.getMailReturnPath());
    }

    // Test custom properties
    public void xtest_customProperties() {
        // Create custom FessEnv with custom properties
        FessEnv.SimpleImpl customEnv = new FessEnv.SimpleImpl() {
            protected Properties prepareProperties() {

### 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.