# Dependencies

**FastAPI** has a very powerful but intuitive **<abbr title="also known as components, resources, providers, services, injectables">Dependency Injection</abbr>** system.

It is designed to be very simple to use, and to make it very easy for any developer to integrate other components with **FastAPI**.

## What is "Dependency Injection"

They are, more or less, at opposite ends, complementing each other.

Requests has a very simple and intuitive design, it's very easy to use, with sensible defaults. But at the same time, it's very powerful and customizable.

That's why, as said in the official website:

> Requests is one of the most downloaded Python packages of all time

The way you use it is very simple. For example, to do a `GET` request, you would write:

```Python

To see how to achieve this parallelism in production see the section about [Deployment](deployment/index.md){.internal-link target=_blank}.

## `async` and `await`

///

```Python hl_lines="8-9"
{!> ../../docs_src/dependencies/tutorial005.py!}
```

////

It declares an optional query parameter `q` as a `str`, and then it just returns it.

This is quite simple (not very useful), but will help us focus on how the sub-dependencies work.

## Second dependency, "dependable" and "dependant"

# GraphQL

As **FastAPI** is based on the **ASGI** standard, it's very easy to integrate any **GraphQL** library also compatible with ASGI.

You can combine normal FastAPI *path operations* with GraphQL on the same application.

/// tip

**GraphQL** solves some very specific use cases.

It has **advantages** and **disadvantages** when compared to common **web APIs**.

   */
  @SuppressWarnings("Java7ApiChecker")
  @IgnoreJRERequirement // Users will use this only if they're already using streams.
  public static ImmutableLongArray copyOf(LongStream stream) {
    // Note this uses very different growth behavior from copyOf(Iterable) and the builder.
    long[] array = stream.toArray();
    return (array.length == 0) ? EMPTY : new ImmutableLongArray(array);
  }

  /**

   *
   * @since 22.0 (but only since 33.4.0 in the Android flavor)
   */
  public static ImmutableIntArray copyOf(IntStream stream) {
    // Note this uses very different growth behavior from copyOf(Iterable) and the builder.
    int[] array = stream.toArray();
    return (array.length == 0) ? EMPTY : new ImmutableIntArray(array);
  }

  /**

/**
 * Immutable identifier of a {@link TransferResource}.
 * The {@link TransferResource} is not immutable and does not implement {@code Objects#equals} and {@code Objects#hashCode} methods,
 * making it not very suitable for usage in collections.
 */
record TransferResourceIdentifier(String repositoryId, String repositoryUrl, String resourceName, @Nullable File file) {
    TransferResourceIdentifier(TransferResource resource) {

import org.apache.maven.api.annotations.Experimental;
import org.apache.maven.api.di.Named;

/**
 * Component able to contribute to Maven session user properties. This SPI component is invoked
 * very early, while there is no session created yet.
 *
 * @since 4.0.0
 */
@Experimental
@Consumer
@Named
public interface PropertyContributor extends SpiService {
    /**

There are many tools to generate clients from **OpenAPI**.

A common tool is <a href="https://openapi-generator.tech/" class="external-link" target="_blank">OpenAPI Generator</a>.

If you are building a **frontend**, a very interesting alternative is <a href="https://github.com/hey-api/openapi-ts" class="external-link" target="_blank">openapi-ts</a>.

## Client and SDK Generators - Sponsor