from fastapi import Body, FastAPI
from pydantic import Field

app = FastAPI()


@app.post("/items/")
async def create_items(items: Annotated[list[int], Field(min_length=1), Body()]):
    return items
```

instead of:

```python
# DO NOT DO THIS
from typing import Annotated

from fastapi import FastAPI
from pydantic import Field, RootModel

app = FastAPI()

- 它會攔截進到應用程式的每個**請求**。
- 然後可以對該**請求**做一些處理或執行所需的程式碼。
- 接著把**請求**傳遞給應用程式的其餘部分（某個*路徑操作*）處理。
- 之後再接收應用程式（某個*路徑操作*）所產生的**回應**。
- 可以對該**回應**做一些處理或執行所需的程式碼。
- 然後回傳**回應**。

/// note | 技術細節

如果你有使用帶有 `yield` 的相依性，其釋放階段的程式碼會在中介軟體之後執行。

若有背景工作（在[背景工作](background-tasks.md)一節會介紹，你稍後會看到），它們會在所有中介軟體之後執行。

///

## 建立中介軟體 { #create-a-middleware }

要建立中介軟體，將裝飾器 `@app.middleware("http")` 加在函式上方。

中介軟體函式會接收：

    @DisplayName("Unknown codes: lookup returns empty Optional")
    void lookup_returns_empty_for_unknown_codes(int unknownCode) {
        // Invalid inputs: codes not present should yield no message
        // Guard to ensure test remains valid if constants change in future
        for (int c : WinError.WINERR_CODES) {

}

/**
 * Returns true if the response headers and status indicate that this response has a (possibly
 * 0-length) body. See RFC 7231.
 */
fun Response.promisesBody(): Boolean {
  // HEAD requests never yield a body regardless of the response headers.
  if (request.method == "HEAD") {
    return false
  }

  val responseCode = code
  if ((responseCode < HTTP_CONTINUE || responseCode >= 200) &&

            log.warn("NTLMv1 NTLM response is deprecated and insecure. Consider using NTLMv2.");
            yield NtlmUtil.getNTLMResponse(getPasswordAsCharArray(), chlng);
        }
        case 3, 4, 5 -> {
            // NTLMv2 - returns empty for unicode hash as NTLMv2 doesn't use it
            yield new byte[0];
        }
        default -> {
            // Default to NTLMv2 behavior (empty response)

    scope: Annotated[
        Literal["function", "request"] | None,
        Doc(
            """
            Mainly for dependencies with `yield`, define when the dependency function
            should start (the code before `yield`) and when it should end (the code
            after `yield`).

            * `"function"`: start the dependency before the *path operation function*

 * A Windows SID is a numeric identifier used to represent Windows
 * accounts. SIDs are commonly represented using a textual format such as
 * {@code S-1-5-21-1496946806-2192648263-3843101252-1029} but they may
 * also be resolved to yield the name of the associated Windows account
 * such as {@code Administrators} or {@code MYDOM\alice}.
 * <p>
 * Consider the following output of {@code examples/SidLookup.java}:
 *
 * <pre>

 * accounts. SIDs are commonly represented using a textual format such as
 * <code>S-1-5-21-1496946806-2192648263-3843101252-1029</code> but they may
 * also be resolved to yield the name of the associated Windows account
 * such as <code>Administrators</code> or <code>MYDOM\alice</code>.
 * <p>
 * Consider the following output of <code>examples/SidLookup.java</code>:
 *
 * <pre>

      afe.initCause(t);
      throw afe;
    }
  }

  /**
   * Delays, via Thread.sleep, for the given millisecond delay, but if the sleep is shorter than
   * specified, may re-sleep or yield until time elapses.
   */
  @SuppressWarnings("ThreadPriorityCheck") // TODO: b/175898629 - Consider onSpinWait?
  static void delay(long millis) throws InterruptedException {
    long startTime = System.nanoTime();

    // a multithreaded environment for a couple of reasons:
    //
    // 1. Subscribers to events posted on different threads can be interleaved with each other
    //    freely. (A event on one thread, B event on another could yield any of
    //    [a1, a2, a3, b1, b2], [a1, b2, a2, a3, b2], [a1, b2, b3, a2, a3], etc.)
    // 2. It's possible for subscribers to actually be dispatched to in a different order than they