加上来自 Starlette（包括 **session cookie**）的所有安全特性。

所有的这些都是可复用的工具和组件，可以轻松与你的系统，数据仓库，关系型以及 NoSQL 数据库等等集成。



### 依赖注入

FastAPI 有一个使用非常简单，但是非常强大的<abbr title='也叫做 "components", "resources", "services", "providers"'><strong>依赖注入</strong></abbr>系统。

* 甚至依赖也可以有依赖，创建一个层级或者**“图”依赖**。
* 所有**自动化处理**都由框架完成。
* 所有的依赖关系都可以从请求中获取数据，并且**增加了路径操作**约束和自动文档生成。
* 即使在依赖项中被定义的*路径操作* 也会**自动验证**。
* 支持复杂的用户身份认证系统，**数据库连接**等等。

   */
  internal var errorCode: ErrorCode? = null
    get() = this.withLock { field }

  /** The exception that explains [errorCode]. Null if no exception was provided. */
  internal var errorException: IOException? = null

  init {
    if (headers != null) {
      check(!isLocallyInitiated) { "locally-initiated streams shouldn't have headers yet" }
      headersQueue += headers

    return checkNotNull(future);
  }

  /**
   * Returns a {@code Future} whose result is taken from this {@code Future} or, if this {@code
   * Future} fails with the given {@code exceptionType}, from the result provided by the {@code
   * fallback}. {@link Function#apply} is not invoked until the primary input has failed, so if the
   * primary input succeeds, it is never invoked. If, during the invocation of {@code fallback}, an

    "s3:ListBucketMultipartUploads",
    "s3:GetBucketLocation",
    "s3:GetBucketVersioning"
   ],
   "Resource": [
    "arn:aws:s3:::srcbucket"
   ]
  }
 ]
}
```

The access key provided for the replication *target* cluster should have these minimal permissions:

```
{
 "Version": "2012-10-17",
 "Statement": [
  {
   "Effect": "Allow",
   "Action": [
    "s3:GetReplicationConfiguration",

	}

	if parsedS3Select.Input.IsEmpty() {
		return errMissingRequiredParameter(fmt.Errorf("InputSerialization must be provided"))
	}

	if parsedS3Select.Output.IsEmpty() {
		return errMissingRequiredParameter(fmt.Errorf("OutputSerialization must be provided"))
	}

	statement, err := sql.ParseSelectStatement(parsedS3Select.Expression)
	if err != nil {
		return err
	}

    assertFailsWith<Exception> {
      badPublicSuffixDatabase.getEffectiveTldPlusOne("squareup.com")
    }.also { e ->
      assertEquals(firstFailure.toString(), e.toString())
    }
  }

  /** These tests are provided by [publicsuffix.org](https://publicsuffix.org/list/). */
  @Test fun publicSuffixDotOrgTestCases() {
    // Any copyright is dedicated to the Public Domain.
    // https://creativecommons.org/publicdomain/zero/1.0/

  val b0 = this[index].code
  val b1 = this[index + 1].code
  return (b0 shl 7) + b1
}

/**
 * An extremely generic binary search that doesn't know what data it's searching over. The caller
 * provides indexes and a comparison function, and this calls that function iteratively.
 *
 * @return the index of the match. If no match is found this is `(-1 - insertionPoint)`, where the

        DependencySelector depFilter = new AndDependencySelector(
                ScopeDependencySelector.legacy(
                        null, Arrays.asList(DependencyScope.TEST.id(), DependencyScope.PROVIDED.id())),
                OptionalDependencySelector.fromDirect(),
                new ExclusionDependencySelector());
        session.setDependencySelector(depFilter);

* Collect the money.
* Send a notification back to the API user (the external developer).
    * This will be done by sending a POST request (from *your API*) to some *external API* provided by that external developer (this is the "callback").

## The normal **FastAPI** app

Let's first see how the normal API app would look like before adding the callback.

And the `dict` you receive as `weights` will actually have `int` keys and `float` values.

///

## Recap

With **FastAPI** you have the maximum flexibility provided by Pydantic models, while keeping your code simple, short and elegant.

But with all the benefits:

* Editor support (completion everywhere!)
* Data conversion (a.k.a. parsing / serialization)
* Data validation