FastAPI is built on top of **Pydantic**, and I have been showing you how to use Pydantic models to declare requests and responses.

But FastAPI also supports using <a href="https://docs.python.org/3/library/dataclasses.html" class="external-link" target="_blank">`dataclasses`</a> the same way:

{* ../../docs_src/dataclasses/tutorial001.py hl[1,7:12,19:20] *}

	// Maximum size for http headers - See: https://docs.aws.amazon.com/AmazonS3/latest/dev/UsingMetadata.html
	maxHeaderSize = 8 * 1024

	// Maximum size for user-defined metadata - See: https://docs.aws.amazon.com/AmazonS3/latest/dev/UsingMetadata.html
	maxUserDataSize = 2 * 1024

	// maxBuckets upto 500000 for any MinIO deployment.
	maxBuckets = 500 * 1000
)

}
```

For more information on when to use `api` and when to use `implementation`,
consult the
[Gradle documentation on API and implementation separation](https://docs.gradle.org/current/userguide/java_library_plugin.html#sec:java_library_separation).

## Snapshots and Documentation

Snapshots of Guava built from the `master` branch are available through Maven
using version `HEAD-jre-SNAPSHOT`, or `HEAD-android-SNAPSHOT` for the Android

 * and {@link java.net.InetAddress}. The name resolution mechanisms
 * used will systematically query all available configured resolution
 * services including WINS, broadcasts, DNS, and LMHOSTS. See
 * <a href="../../resolver.html">Setting Name Resolution Properties</a>
 * and the <code>jcifs.resolveOrder</code> property. Changing
 * jCIFS name resolution properties can greatly affect the behavior of
 * the client and may be necessary for proper operation.

O **JSON Schema** na verdade não tem um campo `example` nos padrões. Versões recentes do JSON Schema definem um campo <a href="https://json-schema.org/draft/2019-09/json-schema-validation.html#rfc.section.9.5" class="external-link" target="_blank">`examples`</a>, mas o OpenAPI 3.0.3 é baseado numa versão mais antiga do JSON Schema que não tinha `examples`.

            </offlineLink>
          </offlineLinks>
          <links>
            <link>https://errorprone.info/api/latest/</link>
          </links>
          <overview>../overview.html</overview>
        </configuration>
      </plugin>
      <plugin>
        <artifactId>maven-resources-plugin</artifactId>
        <executions>
          <execution>
            <id>gradle-module-metadata</id>

 *
 * <p>A {@code CharEscaper} instance is required to be stateless, and safe when used concurrently by
 * multiple threads.
 *
 * <p>Popular escapers are defined as constants in classes like {@link
 * com.google.common.html.HtmlEscapers} and {@link com.google.common.xml.XmlEscapers}. To create
 * your own escapers extend this class and implement the {@link #escape(char)} method.
 *
 * @author Sven Mawson
 * @since 15.0
 */
@GwtCompatible

  source ./ci/official/utilities/setup_docker.sh
fi

# Generate an overview page describing the build
if [[ "$TFCI_INDEX_HTML_ENABLE" == 1 ]]; then
  ./ci/official/utilities/generate_index_html.sh "$TFCI_OUTPUT_DIR/index.html"
fi

# Single handler for all cleanup actions, triggered on an EXIT trap.
# TODO(angerson) Making this use different scripts may be overkill.
cleanup() {
  if [[ "$TFCI_DOCKER_ENABLE" == 1 ]]; then

<img src="/img/tutorial/body-fields/image01.png">

## 技术细节

关于 `example` 和 `examples`...

JSON Schema在最新的一个版本中定义了一个字段 <a href="https://json-schema.org/draft/2019-09/json-schema-validation.html#rfc.section.9.5" class="external-link" target="_blank">`examples`</a> ，但是 OpenAPI 基于之前的一个旧版JSON Schema，并没有 `examples`.

      FluentIterable.of(
              "base",
              "cache",
              "collect",
              "escape",
              "eventbus",
              "graph",
              "hash",
              "html",
              "io",
              "math",
              "net",
              "primitives",
              "reflect",
              "util.concurrent",
              "xml")