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.

And you can also declare body parameters as optional, by setting the default to `None`:

## Use `Annotated`

Always prefer the `Annotated` style for parameter and dependency declarations.

It keeps the function signatures working in other contexts, respects the types, allows reusability.

### In Parameter Declarations

Use `Annotated` for parameter declarations, including `Path`, `Query`, `Header`, etc.:

```python
from typing import Annotated

 *   <li><strong>Duplicate Dependencies</strong>: Removes duplicate dependency declarations that Maven 4 strictly validates</li>
 *   <li><strong>Duplicate Plugins</strong>: Removes duplicate plugin declarations that Maven 4 strictly validates</li>
 *   <li><strong>Unsupported Repository Expressions</strong>: Comments out repositories with expressions not supported by Maven 4</li>

## Pydantic { #pydantic }

All the data validation is performed under the hood by [Pydantic](https://docs.pydantic.dev/), so you get all the benefits from it. And you know you are in good hands.

You can use the same type declarations with `str`, `float`, `bool` and many other complex data types.

Several of these are explored in the next chapters of the tutorial.

## Order matters { #order-matters }

**FastAPI** gives you the following:

### Based on open standards { #based-on-open-standards }

* [**OpenAPI**](https://github.com/OAI/OpenAPI-Specification) for API creation, including declarations of <dfn title="also known as: endpoints, routes">path</dfn> <dfn title="also known as HTTP methods, as POST, GET, PUT, DELETE">operations</dfn>, parameters, request bodies, security, etc.

   */

  @Override
  public Object[] toArray() {
    return snapshotElementsToList().toArray();
  }

  @Override
  @SuppressWarnings("nullness") // b/192354773 in our checker affects toArray declarations
  public <T extends @Nullable Object> T[] toArray(T[] array) {
    return snapshotElementsToList().toArray(array);
  }

  /*
   * We'd love to use 'new ArrayList(this)' or 'list.addAll(this)', but

But you can re-order them, and have the value without a default (the query parameter `q`) first.

It doesn't matter for **FastAPI**. It will detect the parameters by their names, types and default declarations (`Query`, `Path`, etc), it doesn't care about the order.

So, you can declare your function as:

{* ../../docs_src/path_params_numeric_validations/tutorial002_py310.py hl[7] *}

Then I contributed to it, to make it fully compliant with JSON Schema, to support different ways to define constraint declarations, and to improve editor support (type checks, autocompletion) based on the tests in several editors.

During the development, I also contributed to [**Starlette**](https://www.starlette.dev/), the other key requirement.

We could do better.

We can declare a `UserBase` model that serves as a base for our other models. And then we can make subclasses of that model that inherit its attributes (type declarations, validation, etc).

All the data conversion, validation, documentation, etc. will still work as normally.

        @SuppressWarnings("nullness")
        Object[] result = standardToArray();
        return result;
      }

      @Override
      @SuppressWarnings("nullness") // b/192354773 in our checker affects toArray declarations
      public <T extends @Nullable Object> T[] toArray(T[] array) {
        return standardToArray(array);
      }
    };
  }

  @Override
  @CanIgnoreReturnValue