{* ../../docs_src/cookie_param_models/tutorial001_an_py310.py hl[9:12,16] *}

**FastAPI** will **extract** the data for **each field** from the **cookies** received in the request and give you the Pydantic model you defined.

## Check the Docs { #check-the-docs }

You can see the defined cookies in the docs UI at `/docs`:

<div class="screenshot">

- **I/O Operations** (`org.codelibs.core.io`) - File handling, resource management, stream utilities, and traversal utilities for efficient resource processing
- **Reflection** (`org.codelibs.core.lang`) - Class loading, method/field access, type introspection utilities, and generics support
- **Exception Handling** (`org.codelibs.core.exception`) - Runtime exception wrappers for common checked exceptions with consistent error handling

### Modern Java 21 Support

	Description  string         `xml:"-" json:"description,omitempty"`

	// Deprecated: In favor of Description - when reading credentials from
	// storage the value of this field is placed in the Description field above
	// if the existing Description from storage is empty.
	Comment string `xml:"-" json:"comment,omitempty"`
}

func (cred Credentials) String() string {
	var s strings.Builder

    /**
     * Creates a NetBIOS session message header.
     * The header format is:
     * - Byte 0: Message type (0x00 for SESSION_MESSAGE)
     * - Byte 1: High bit of 17-bit length field
     * - Bytes 2-3: Lower 16 bits of length field
     */
    private static byte[] messageHeader(int length) {
        byte[] h = new byte[4];
        h[0] = (byte) SessionServicePacket.SESSION_MESSAGE;

```JSON
{
  "detail": [
    {
      "type": "missing",
      "loc": [
        "query",
        "needy"
      ],
      "msg": "Field required",
      "input": null
    }
  ]
}
```

Da `needy` ein erforderlicher Parameter ist, müssen Sie ihn in der URL setzen:

```
http://127.0.0.1:8000/items/foo-item?needy=sooooneedy
```

本例把标准的 `dataclasses` 直接替换为 `pydantic.dataclasses`：

```{ .python .annotate hl_lines="1  5  8-11  14-17  23-25  28" }
{!../../docs_src/dataclasses_/tutorial003.py!}
```

1. 本例依然要从标准的 `dataclasses` 中导入 `field`；

2. 使用 `pydantic.dataclasses` 直接替换 `dataclasses`；

3. `Author` 数据类包含 `Item` 数据类列表；

4. `Author` 数据类用于 `response_model` 参数；

5. 其它带有数据类的标准类型注解也可以作为请求体；

    本例使用的是 `Item` 数据类列表；

        }
        // Convert milliseconds to 100-nanosecond intervals
        // 1 ms = 10,000 * 100ns intervals
        long intervals = timeoutMs * 10000L;
        // MS-SMB2 timeout field is 4 bytes (uint32), so clamp to max value
        return Math.min(intervals, 0xFFFFFFFFL);
    }

    /**
     * Get the flags
     * @return the flags
     */
    public int getFlags() {

  /*
   * Per JDK: "the behavior of a map entry is undefined if the backing map has been modified after
   * the entry was returned by the iterator, except through the setValue operation on the map entry"
   * As such, this field must be cleared before every map mutation.
   *
   * Note about volatile: volatile doesn't make it safe to read from a mutable graph in one thread

 * should be handled, including its source, type, default value, and whether it's read-only.
 *
 * @since 4.0.0
 */
@Experimental
@Documented
@Retention(RetentionPolicy.CLASS)
@Target(ElementType.FIELD)
public @interface Config {

    /**
     * Specifies the source of the configuration property, which determines when and where the property
     * will be read from or set for consumption in the Maven build lifecycle.

    public interface ContentTransformer {
        /**
         * Interpolate the value read from the xpp3 document
         * @param source The source value
         * @param fieldName A description of the field being interpolated. The implementation may use this to
         *                           log stuff.
         * @return The interpolated value.
         */
        String transform(String source, String fieldName);