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`:

  }

  @Override
  public @Nullable Object[] toArray() {
    return standardToArray();
  }

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

  @Override
  public String toString() {
    return entrySet().toString();
  }

  }

  @Override
  public @Nullable Object[] toArray() {
    return standardToArray();
  }

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

  @Override
  public String toString() {
    return entrySet().toString();
  }

## 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>

          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);
        }
      };
    }

## 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 }

      @Override
      public @Nullable Object[] toArray() {
        return ObjectArrays.toArrayImpl(this);
      }

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

      @Override
      public Spliterator<K> spliterator() {

        "sec:controlling_dependency_caching_programmatically",
        "sec:offline-mode",
        "sec:controlling_dependency_caching_command_line",
        "sec:dynamic_versions_and_changing_modules",
        "single-version-declarations",
        "version_ordering",
        "sec:declaring_without_version",
        "rich-version-constraints",
        "dependency_management_in_gradle",
        "sec:dependency-mgmt-in-gradle"
    ));

  }

  @Override
  public @Nullable Object[] toArray() {
    return standardToArray();
  }

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

  @Override
  public String toString() {
    return entrySet().toString();
  }