# 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`. 🤓

///

   * it is returned directly. Otherwise, a new array of size {@code minLength + padding} is
   * returned, containing the values of {@code array}, and zeroes in the remaining places.
   *
   * @param array the source array
   * @param minLength the minimum length the returned array must guarantee
   * @param padding an extra amount to "grow" the array by if growth is necessary

# Cookie Parameter Models { #cookie-parameter-models }

If you have a group of **cookies** 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`. 🤓

///

/// tip

# General - How To - Recipes { #general-how-to-recipes }

Here are several pointers to other places in the docs, for general or frequent questions.

## Filter Data - Security { #filter-data-security }

To ensure that you don't return more data than you should, read the docs for [Tutorial - Response Model - Return Type](../tutorial/response-model.md).

import com.google.common.annotations.J2ktIncompatible;
import java.io.Closeable;
import java.io.Flushable;
import java.io.IOException;
import java.io.Writer;
import org.jspecify.annotations.Nullable;

/**
 * Writer that places all output on an {@link Appendable} target. If the target is {@link Flushable}
 * or {@link Closeable}, flush()es and close()s will also be delegated to the target.
 *
 * @author Alan Green
 * @author Sebastian Kanthak

# 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`. 🤓

///

   * it is returned directly. Otherwise, a new array of size {@code minLength + padding} is
   * returned, containing the values of {@code array}, and zeroes in the remaining places.
   *
   * @param array the source array
   * @param minLength the minimum length the returned array must guarantee
   * @param padding an extra amount to "grow" the array by if growth is necessary

 * @since 2.0
 */
@GwtCompatible
public abstract class ForwardingMapEntry<K extends @Nullable Object, V extends @Nullable Object>
    extends ForwardingObject implements Map.Entry<K, V> {
  // TODO(lowasser): identify places where thread safety is actually lost

  /** Constructor for use by subclasses. */
  protected ForwardingMapEntry() {}

  @Override
  protected abstract Entry<K, V> delegate();

  @Override

            """
        ),
    ] = _Unset,
    decimal_places: Annotated[
        int | None,
        Doc(
            """
            Maximum number of decimal places allowed for decimal values.
            """
        ),
    ] = _Unset,
    examples: Annotated[
        list[Any] | None,
        Doc(
            """
            Example values for this field.

   * it is returned directly. Otherwise, a new array of size {@code minLength + padding} is
   * returned, containing the values of {@code array}, and zeroes in the remaining places.
   *
   * @param array the source array
   * @param minLength the minimum length the returned array must guarantee
   * @param padding an extra amount to "grow" the array by if growth is necessary