In this case, the function parameter `q` will be optional, and will be `None` by default.

/// check

Also notice that **FastAPI** is smart enough to notice that the path parameter `item_id` is a path parameter and `q` is not, so, it's a query parameter.

///

## Query parameter type conversion { #query-parameter-type-conversion }

You can also declare `bool` types, and they will be converted:

    /**
     * Add the created action message for the key 'constraints.Size.message' with parameters.
     * <pre>
     * message: The size of {item} must be between {min} and {max}.
     * </pre>
     * @param property The property name for the message. (NotNull)
     * @param min The parameter min for message. (NotNull)
     * @param max The parameter max for message. (NotNull)
     * @return this. (NotNull)
     */

# Body - Multiple Parameters { #body-multiple-parameters }

Now that we have seen how to use `Path` and `Query`, let's see more advanced uses of request body declarations.

## Mix `Path`, `Query` and body parameters { #mix-path-query-and-body-parameters }

First, of course, you can mix `Path`, `Query` and request body parameter declarations freely and **FastAPI** will know what to do.

# Query Parameter Models { #query-parameter-models }

If you have a group of **query parameters** that are related, you can create a **Pydantic model** to declare them.

This would allow you to **re-use the model** in **multiple places** and also to declare validations and metadata for all the parameters at once. 😎

/// note

This is supported since FastAPI version `0.115.0`. 🤓

///

# Header Parameter Models { #header-parameter-models }

If you have a group of related **header parameters**, you can create a **Pydantic model** to declare them.

This would allow you to **re-use the model** in **multiple places** and also to declare validations and metadata for all the parameters at once. 😎

/// note

This is supported since FastAPI version `0.115.0`. 🤓

///

# Header Parameters { #header-parameters }

You can define Header parameters the same way you define `Query`, `Path` and `Cookie` parameters.

## Import `Header` { #import-header }

First import `Header`:

{* ../../docs_src/header_params/tutorial001_an_py310.py hl[3] *}

## Declare `Header` parameters { #declare-header-parameters }

Then declare the header parameters using the same structure as with `Path`, `Query` and `Cookie`.

                    logger.warn("Failed to store search parameters in cookie.", e);
                }
            }
        });
    }

    /**
     * Serializes request parameters to a compressed and encoded string.
     *
     * @param parameters Array of request parameters to serialize
     * @return Base64-encoded, GZIP-compressed JSON string of parameters
     * @throws SearchQueryException if serialization fails

{* ../../docs_src/body/tutorial002_py310.py *}

## Request body + path parameters { #request-body-path-parameters }

You can declare path parameters and request body at the same time.

**FastAPI** will recognize that the function parameters that match path parameters should be **taken from the path**, and that function parameters that are declared to be Pydantic models should be **taken from the request body**.

# Path Parameters and Numeric Validations { #path-parameters-and-numeric-validations }

In the same way that you can declare more validations and metadata for query parameters with `Query`, you can declare the same type of validations and metadata for path parameters with `Path`.

## Import `Path` { #import-path }

First, import `Path` from `fastapi`, and import `Annotated`:

{* ../../docs_src/path_params_numeric_validations/tutorial001_an_py310.py hl[1,3] *}

 * If this parameter is not present, an empty string is returned as the content.</p>
 */
public class FilenameExtractor extends AbstractExtractor {

    /**
     * Constructs a new FilenameExtractor.
     */
    public FilenameExtractor() {
        // Default constructor
    }

    /**
     * Extracts the filename from the parameters.
     *