# Middleware (Проміжний шар)

У **FastAPI** можна додавати middleware (проміжний шар).

"Middleware" — це функція, яка працює з кожним **запитом** перед його обробкою будь-якою конкретною *операцією шляху* (*path operation*), а також з кожною **відповіддю** перед її поверненням.

* Middleware отримує кожен **запит**, що надходить до Вашого застосунку.
* Може виконати певні дії із цим **запитом** або запустити необхідний код.

# Background Tasks - `BackgroundTasks`

You can declare a parameter in a *path operation function* or dependency function with the type `BackgroundTasks`, and then you can use it to schedule the execution of background tasks after the response is sent.

You can import it directly from `fastapi`:

```python
from fastapi import BackgroundTasks
```

In this case, this `__call__` is what **FastAPI** will use to check for additional parameters and sub-dependencies, and this is what will be called to pass a value to the parameter in your *path operation function* later.

## Parameterize the instance { #parameterize-the-instance }

And now, we can use `__init__` to declare the parameters of the instance that we can use to "parameterize" the dependency:

            result = buf.dec_ndr_long();
        } else { /* Bind_ack or Response */
            decode_out(buf);
        }
    }

    /**
     * Get the operation number for this DCERPC message.
     * @return the operation number
     */
    public abstract int getOpnum();

    /**
     * Encode the input parameters for this DCERPC message.
     * @param buf the buffer to encode into

 * matches the insertion order. All optional operations (adding and removing) are supported. All
 * elements, including {@code null}, are permitted.
 *
 * <p>{@code contains(x)}, {@code add(x)} and {@code remove(x)}, are all (expected and amortized)
 * constant time operations. Expected in the hashtable sense (depends on the hash function doing a

  }

  @Override
  public int count(@Nullable Object element) {
    Count frequency = safeGet(backingMap, element);
    return (frequency == null) ? 0 : frequency.get();
  }

  // Optional Operations - Modification Operations

  /**
   * {@inheritDoc}
   *
   * @throws IllegalArgumentException if the call would result in more than {@link
   *     Integer#MAX_VALUE} occurrences of {@code element} in this multiset.

 * matches the insertion order. All optional operations (adding and removing) are supported. All
 * elements, including {@code null}, are permitted.
 *
 * <p>{@code contains(x)}, {@code add(x)} and {@code remove(x)}, are all (expected and amortized)
 * constant time operations. Expected in the hashtable sense (depends on the hash function doing a

	)

	ErrInvalidNumberOfErasureEndpoints = newErrFn(
		"Invalid total number of endpoints for erasure mode",
		"Please provide number of endpoints greater or equal to 2",
		"For more information, please refer to https://docs.min.io/community/minio-object-store/operations/concepts/erasure-coding.html",
	)

import org.codelibs.fess.util.ComponentUtil;

/**
 * FessIntervalController extends DefaultIntervalController to provide
 * Fess-specific interval control functionality for web crawling operations.
 * This controller manages delays and timing for various crawling states
 * including processing delays, queue waiting times, and new URL discovery.
 */
public class FessIntervalController extends DefaultIntervalController {

# Body - Fields { #body-fields }

The same way you can declare additional validation and metadata in *path operation function* parameters with `Query`, `Path` and `Body`, you can declare validation and metadata inside of Pydantic models using Pydantic's `Field`.

## Import `Field` { #import-field }

First, you have to import it:

{* ../../docs_src/body_fields/tutorial001_an_py310.py hl[4] *}


/// warning