* </p>
 * <ul>
 *   <li>Normalizing text content</li>
 *   <li>Handling resource names and content types</li>
 *   <li>Retrying extraction without resource name or content type if the initial attempt fails</li>
 *   <li>Extracting text from metadata if the main content extraction fails</li>
 *   <li>Reading content as plain text if all other methods fail</li>

                    if (errorCount > maxErrorCount) {
                        throw e;
                    }
                    errorCount++;
                    logger.warn("Failed to access AccessResult data. Retrying... (attempt={}/{})", errorCount, maxErrorCount, e);
                } finally {
                    if (systemHelper.isForceStop()) {
                        finishCrawling = true;

The benefit of raising an exception over returning a value will be more evident in the section about Dependencies and Security.

In this example, when the client requests an item by an ID that doesn't exist, raise an exception with a status code of `404`:

/// tip

Now we use `response_model=HeroPublic` instead of the **return type annotation** `-> HeroPublic` because the value that we are returning is actually *not* a `HeroPublic`.

If we had declared `-> HeroPublic`, your editor and linter would complain (rightfully so) that you are returning a `Hero` instead of a `HeroPublic`.

In this example, the function `generate_html_response()` already generates and returns a `Response` instead of returning the HTML in a `str`.

By returning the result of calling `generate_html_response()`, you are already returning a `Response` that will override the default **FastAPI** behavior.

FastAPI will use this return type to:

* **Validate** the returned data.
    * If the data is invalid (e.g. you are missing a field), it means that *your* app code is broken, not returning what it should, and it will return a server error instead of returning incorrect data. This way you and your clients can be certain that they will receive the data and the data shape expected.
* Add a **JSON Schema** for the response, in the OpenAPI *path operation*.

You can add middleware to **FastAPI** applications.

A "middleware" is a function that works with every **request** before it is processed by any specific *path operation*. And also with every **response** before returning it.

* It takes each **request** that comes to your application.
* It can then do something to that **request** or run any needed code.

You can also declare the `Response` parameter in dependencies, and set cookies (and headers) in them.

## Return a `Response` directly { #return-a-response-directly }

You can also create cookies when returning a `Response` directly in your code.

To do that, you can create a response as described in [Return a Response Directly](response-directly.md){.internal-link target=_blank}.

Then set Cookies in it, and then return it:

**FastAPI** provides the same `starlette.responses` as `fastapi.responses` just as a convenience for you, the developer. But most of the available responses come directly from Starlette.

///

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

5. You can use other standard type annotations with dataclasses as the request body.

    In this case, it's a list of `Item` dataclasses.

6. Here we are returning a dictionary that contains `items` which is a list of dataclasses.

    FastAPI is still capable of <abbr title="converting the data to a format that can be transmitted">serializing</abbr> the data to JSON.