* This class provides methods for converting binary data to readable hex format.
 */

public class Hexdump {

    /**
     * Default constructor.
     */
    public Hexdump() {
        // Utility class - no instance variables to initialize
    }

    /**
     * Array of hexadecimal digit characters used for converting binary data to hex representation.
     */

 */
package jcifs.util;

import jcifs.Encodable;

/**
 * Interface for objects that can be encoded to byte arrays.
 * Provides standardized method for converting objects to their binary representation.
 *
 * @author mbechler
 */
public class ByteEncodable implements Encodable {

    private final byte[] bytes;
    private final int off;
    private final int len;

Because **FastAPI** doesn't make any changes to a `Response` you return, you have to make sure its contents are ready for it.

For example, you cannot put a Pydantic model in a `JSONResponse` without first converting it to a `dict` with all the data types (like `datetime`, `UUID`, etc) converted to JSON-compatible types.

For those cases, you can use the `jsonable_encoder` to convert your data before passing it to a response:

* `frozenset`:
    * In requests and responses, treated the same as a `set`:
        * In requests, a list will be read, eliminating duplicates and converting it to a `set`.
        * In responses, the `set` will be converted to a `list`.
        * The generated schema will specify that the `set` values are unique (using JSON Schema's `uniqueItems`).
* `bytes`:

    ]
}
```

## Recap { #recap }

Declare headers with `Header`, using the same common pattern as `Query`, `Path` and `Cookie`.

{"item_id":3}
```

/// check

Notice that the value your function received (and returned) is `3`, as a Python `int`, not a string `"3"`.

So, with that type declaration, **FastAPI** gives you automatic request <abbr title="converting the string that comes from an HTTP request into Python data">"parsing"</abbr>.

///

## Data validation { #data-validation }

{"item_id":3}
```

/// check | Revisa

Nota que el valor que tu función recibió (y devolvió) es `3`, como un `int` de Python, no un string `"3"`.

Entonces, con esa declaración de tipo, **FastAPI** te ofrece <abbr title="converting the string that comes from an HTTP request into Python data">"parsing"</abbr> automático de requests.

///

## Validación de datos

import com.google.errorprone.annotations.CanIgnoreReturnValue;
import java.nio.ByteBuffer;
import java.nio.ByteOrder;
import org.jspecify.annotations.Nullable;

/**
 * Abstract {@link Hasher} that handles converting primitives to bytes using a scratch {@code
 * ByteBuffer} and streams all bytes to a sink to compute the hash.
 *
 * @author Colin Decker
 */
abstract class AbstractByteHasher extends AbstractHasher {

    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.

7. Here the `response_model` is using a type annotation of a list of `Author` dataclasses.

Taking data from:

* The path as parameters.
* Headers.
* Cookies.
* etc.

And by doing so, **FastAPI** is validating that data, converting it and generating documentation for your API automatically.

But there are situations where you might need to access the `Request` object directly.

## Details about the `Request` object { #details-about-the-request-object }