**FastAPI** 将从请求中接收到的 **headers** 中**提取**出**每个字段**的数据，并提供您定义的 Pydantic 模型。

## 查看文档 { #check-the-docs }

您可以在文档 UI 的 `/docs` 中查看所需的 headers：

<div class="screenshot">
<img src="/img/tutorial/header-param-models/image01.png">
</div>

## 禁止额外的 Headers { #forbid-extra-headers }

在某些特殊使用情况下（可能并不常见），您可能希望**限制**您想要接收的 headers。

您可以使用 Pydantic 的模型配置来禁止（ `forbid` ）任何额外（ `extra` ）字段：

  @Test fun basicChallenge() {
    val headers =
      Headers
        .Builder()
        .add("WWW-Authenticate: Basic realm=\"protected area\"")
        .build()
    assertThat(headers.parseChallenges("WWW-Authenticate"))
      .isEqualTo(listOf(Challenge("Basic", mapOf("realm" to "protected area"))))
  }

  @Test fun basicChallengeWithCharset() {
    val headers =
      Headers
        .Builder()

        method = self.METHOD

        def fetch_credentials():
            # HTTP headers are case insensitive filter out
            # all duplicate headers and pick one.
            headers = {}
            headers['content-type'] = 'application/x-www-form-urlencoded'
            headers['authorization'] = urllib3.make_headers(
                basic_auth='%s:%s' % (self.cid, self.csec))['authorization']

		w.compressors = make(map[uint16]Compressor)
	}
	w.compressors[method] = comp
}

// AddFS adds the files from fs.FS to the archive.
// It walks the directory tree starting at the root of the filesystem
// adding each file to the zip using deflate while maintaining the directory structure.
func (w *Writer) AddFS(fsys fs.FS) error {
	return fs.WalkDir(fsys, ".", func(name string, d fs.DirEntry, err error) error {

    val expected = Date(0L)
    val headers =
      Headers
        .Builder()
        .add("testDate", expected)
        .build()
    assertThat(headers["testDate"]).isEqualTo("Thu, 01 Jan 1970 00:00:00 GMT")
    assertThat(headers.getDate("testDate")).isEqualTo(Date(0L))
  }

  @Test fun addInstant() {
    val expected = Instant.ofEpochMilli(0L)
    val headers =
      Headers
        .Builder()

    /**
     * Returns the subset of the headers in [requestHeaders] that impact the content of the
     * response's body.
     */
    private fun varyHeaders(
      requestHeaders: Headers,
      responseHeaders: Headers,
    ): Headers {
      val varyFields = responseHeaders.varyFields()
      if (varyFields.isEmpty()) return Headers.EMPTY

      val result = Headers.Builder()

    val authority = request.headers["Host"] // Has host and port.
    val fancyRequest =
      Request
        .Builder()
        .url("$scheme://$authority/")
        .headers(request.headers)
        .build()
    val fancyResponse =
      Response
        .Builder()
        .code(webSocketResponse.code)
        .message(webSocketResponse.message)
        .headers(webSocketResponse.headers)

import mockwebserver3.internal.decodeRequestLine
import okhttp3.Headers
import okhttp3.Headers.Companion.headersOf
import okio.Buffer
import okio.ByteString
import org.junit.jupiter.api.Test
import org.junit.jupiter.api.Timeout

@Timeout(30)
class RecordedRequestTest {
  private val headers: Headers = Headers.EMPTY

  @Test fun testIPv4() {
    val socket =
      MockWebServerSocket(

  internal constructor(
    requestLine: String,
    headers: Headers,
    chunkSizes: List<Int>,
    bodySize: Long,
    body: Buffer,
    sequenceNumber: Int,
    failure: IOException?,
    method: String?,
    path: String?,
    handshake: Handshake?,
    requestUrl: HttpUrl?,
  ) {
    this.requestLine = requestLine
    this.headers = headers
    this.chunkSizes = chunkSizes
    this.bodySize = bodySize

        }

        value = props.getProperty("jcifs.netbios.laddr");
        if (value != null) {
            try {
                this.netbiosLocalAddress = InetAddress.getByName(value);
            } catch (UnknownHostException e) {
                // Invalid address ignored
            }
        }

        value = props.getProperty("jcifs.netbios.baddr");
        if (value != null) {
            try {