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：

{* ../../docs_src/header_param_models/tutorial002_an_py310.py hl[10] *}

如果客户尝试发送一些**额外的 headers**，他们将收到**错误**响应。

from fastapi import FastAPI, Header
from pydantic import BaseModel

app = FastAPI()


class CommonHeaders(BaseModel):
    model_config = {"extra": "forbid"}

    host: str
    save_data: bool
    if_modified_since: str | None = None
    traceparent: str | None = None
    x_tag: list[str] = []


@app.get("/items/")
async def read_items(headers: CommonHeaders = Header()):

from typing import Annotated

from fastapi import FastAPI, Header
from pydantic import BaseModel

app = FastAPI()


class CommonHeaders(BaseModel):
    model_config = {"extra": "forbid"}

    host: str
    save_data: bool
    if_modified_since: str | None = None
    traceparent: str | None = None
    x_tag: list[str] = []


@app.get("/items/")
async def read_items(headers: Annotated[CommonHeaders, Header()]):

 * under the License.
 */
package org.apache.maven.toolchain.io;

import java.io.IOException;

/**
 * Signals a failure to parse the toolchains due to invalid syntax (e.g. non well-formed XML or unknown elements).
 *
 * @since 3.3.0
 */
@Deprecated(since = "4.0.0")
public class ToolchainsParseException extends IOException {

    /**
     * The one-based index of the line containing the error.

}

func (err *s3Error) Error() string {
	return err.message
}

func errMalformedXML(err error) *s3Error {
	return &s3Error{
		code:       "MalformedXML",
		message:    "The XML provided was not well-formed or did not validate against our published schema. Check the service documentation and try again: " + err.Error(),
		statusCode: 400,
		cause:      err,
	}
}

func errInvalidCompressionFormat(err error) *s3Error {

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

## 禁止额外的表单字段 { #forbid-extra-form-fields }

在某些特殊使用情况下（可能并不常见），你可能希望将表单字段**限制**为仅在 Pydantic 模型中声明过的字段，并**禁止**任何**额外**的字段。

/// note | 注意

自 FastAPI 版本 `0.114.0` 起支持此功能。🤓

///

你可以使用 Pydantic 的模型配置来 `forbid` 任何 `extra` 字段：

{* ../../docs_src/request_form_models/tutorial002_an_py310.py hl[12] *}

     * changes: https://mail.openjdk.org/pipermail/core-libs-dev/2013-May/thread.html#17367
     *
     * TODO(cpovirk): decide what the best long-term action here is: force users
     * to suppress (as we do now), stop testing entrySet().add() at all, make
     * entrySet().add() tests tolerant of either behavior, introduce a map
     * feature for entrySet() that supports add(), or something else

        @Test
        @DisplayName("list propagates SmbUnsupportedOperationException from doEnum")
        void list_propagatesUnsupportedOperationException() throws Exception {
            // Arrange: same setup as above to force doEnum -> SmbUnsupportedOperationException
            SmbFile parent = mock(SmbFile.class, RETURNS_DEEP_STUBS);
            SmbResourceLocator locator = mock(SmbResourceLocator.class);

import java.lang.annotation.RetentionPolicy;
import java.lang.reflect.Method;
import java.util.Locale;
import junit.framework.TestCase;

/**
 * Since annotations have some reusability issues that force copy and paste all over the place, it's
 * worth having a test to ensure that all our Feature enums have their annotations correctly set up.
 *
 * @author George van den Driessche
 */

            logger.info("Deleted completed document data: time={}ms", systemHelper.getCurrentTimeAsLong() - execTime);
        }
    }

    /**
     * Forces all crawlers to stop immediately.
     * Sets the force stop flag and stops all active crawler instances.
     */
    private void forceStop() {
        systemHelper.setForceStop(true);
        if (crawlerList != null) {