## An app with callbacks { #an-app-with-callbacks }

Let's see all this with an example.

Imagine you develop an app that allows creating invoices.

These invoices will have an `id`, `title` (optional), `customer`, and `total`.

The user of your API (an external developer) will create an invoice in your API with a POST request.

Then your API will (let's imagine):

But because of our changes in `GzipRequest.body`, the request body will be automatically decompressed when it is loaded by **FastAPI** when needed.

## Accessing the request body in an exception handler { #accessing-the-request-body-in-an-exception-handler }

/// tip

      }
      Class<?> returnType = method.getReturnType();
      assertTrue(
          rootLocaleFormat("%s.%s() must return an array.", annotationClass, propertyName),
          returnType.isArray());
      assertWithMessage(
              rootLocaleFormat(
                  "%s.%s() must return an array of %s.",
                  annotationClass, propertyName, annotationClass.getDeclaringClass()))

So, in a URL like:

```
https://example.com/items/foo
```

...the path would be:

```
/items/foo
```

/// info

A "path" is also commonly called an "endpoint" or a "route".

///

While building an API, the "path" is the main way to separate "concerns" and "resources".

#### Operation { #operation }

"Operation" here refers to one of the HTTP "methods".

One of:

     * uses registered DictionaryCreator instances to create appropriate
     * DictionaryFile objects.
     *
     * @return an array of dictionary files available in the system
     * @throws DictionaryException if there's an error accessing the dictionaries
     */
    public DictionaryFile<? extends DictionaryItem>[] getDictionaryFiles() {
        try (CurlResponse response = ComponentUtil.getCurlHelper()

    /**
     * SID type for a domain.
     */
    public static final int SID_TYPE_DOMAIN = 3;

    /**
     * SID type for an invalid SID.
     */
    public static final int SID_TYPE_INVALID = 7;

    /**
     * SID type for an unknown SID.
     */
    public static final int SID_TYPE_UNKNOWN = 8;

    /**
     * SID type for a non-use SID.
     */

/// info

Webhooks are available in OpenAPI 3.1.0 and above, supported by FastAPI `0.99.0` and above.

///

## An app with webhooks { #an-app-with-webhooks }

When you create a **FastAPI** application, there is a `webhooks` attribute that you can use to define *webhooks*, the same way you would define *path operations*, for example with `@app.webhooks.post()`.

tells SQLModel that the `id` is the **primary key** in the SQL database (you can learn more about SQL primary keys in the SQLModel docs).

    **Note:** We use `int | None` for the primary key field so that in Python code we can *create an object without an `id`* (`id=None`), assuming the database will *generate it when saving*. SQLModel understands that the database will provide the `id` and *defines the column as a non-null `INTEGER`* in the database schema. See <a href="https://sqlmodel.ti...

                * Serialization: you could return an arbitrary object and the
                    `response_model` would be used to serialize that object into the
                    corresponding JSON.
                * Filtering: the JSON sent to the client will only contain the data
                    (fields) defined in the `response_model`. If you returned an object
                    that contains an attribute `password` but the `response_model` does

        "detail": [
            {
                "type": "int_parsing",
                "loc": ["path", "item_id"],
                "msg": "Input should be a valid integer, unable to parse string as an integer",
                "input": "foobar",
            }
        ]
    }


def test_path_int_True():
    response = client.get("/path/int/True")
    assert response.status_code == 422