* der Inhalt einer Datei vom System von der Festplatte gelesen und an Ihr Programm übergeben wurde
* der Inhalt, den Ihr Programm dem System übergeben hat, auf die Festplatte geschrieben wurde
* eine Remote-API-Operation beendet wurde
* Eine Datenbankoperation abgeschlossen wurde
* eine Datenbankabfrage die Ergebnisse zurückgegeben hat
* usw.

     *
     * In theory, we can quickly determine the size of any Collection. However, thanks to
     * regrettable implementations like our own Sets.filter, Collection.size() is sometimes a
     * linear-time operation, and it can even have side effects. Thus, we limit the special case to
     * List, which is _even more likely_ to have size() implemented to be fast and side-effect-free.
     *

 * inserted by producers and extracted by consumers. Once created, the capacity cannot be increased.
 * Attempts to {@code put} an element into a full queue will result in the operation blocking;
 * attempts to {@code take} an element from an empty queue will similarly block.
 *
 * <p>This class supports an optional fairness policy for ordering waiting producer and consumer

            if (existing != null) {
                return existing;
            }
        }

        // Check pool size limits using atomic operation
        if (!nonPooled) {
            int currentSize = this.connections.size();
            if (currentSize >= maxPoolSize) {
                // Try to remove idle connections
                removeIdleConnections();

{* ../../docs_src/settings/app02_an_py310/main.py hl[6,12:13] *}

/// tip | 豆知識

`@lru_cache` については後で説明します。

今は `get_settings()` が普通の関数だと考えてください。

///

そして、*path operation 関数*から依存関係として要求し、必要な場所でどこでも使えます。

{* ../../docs_src/settings/app02_an_py310/main.py hl[17,19:21] *}

### 設定とテスト { #settings-and-testing }

次に、`get_settings` の依存関係オーバーライドを作ることで、テスト中に別の設定オブジェクトを提供するのがとても簡単になります:

Kullanımı çok basittir. Örneğin bir `GET` isteği yapmak için:

```Python
response = requests.get("http://example.com/some/url")
```

Buna karşılık bir FastAPI API *path operation*’ı şöyle olabilir:

```Python hl_lines="1"
@app.get("/some/url")
def read_url():
    return {"message": "Hello World"}
```

`requests.get(...)` ile `@app.get(...)` arasındaki benzerliklere bakın.

更新 `get_current_user`，讓它仍接收相同的權杖，但這次改用 JWT 權杖。

解碼收到的權杖、驗證它，並回傳目前的使用者。

如果權杖無效，立即回傳一個 HTTP 錯誤。

{* ../../docs_src/security/tutorial004_an_py310.py hl[93:110] *}

## 更新 `/token` 路徑操作 { #update-the-token-path-operation }

用權杖有效期建立一個 `timedelta`。

建立真正的 JWT access token 並回傳它。

{* ../../docs_src/security/tutorial004_an_py310.py hl[121:136] *}

### 關於 JWT「主體」`sub` 的技術細節 { #technical-details-about-the-jwt-subject-sub }

解码接收到的令牌，进行校验，并返回当前用户。

如果令牌无效，立即返回一个 HTTP 错误。

{* ../../docs_src/security/tutorial004_an_py310.py hl[93:110] *}

## 更新 `/token` 路径操作 { #update-the-token-path-operation }

用令牌的过期时间创建一个 `timedelta`。

创建一个真正的 JWT 访问令牌并返回它。

{* ../../docs_src/security/tutorial004_an_py310.py hl[121:136] *}

### 关于 JWT “主题” `sub` 的技术细节 { #technical-details-about-the-jwt-subject-sub }

// If block is false, Read and Write will return ErrIsEmpty or ErrIsFull immediately.
// By default, the ring buffer is not blocking.
// This setting should be called before any Read or Write operation or after a Reset.
func (r *RingBuffer) SetBlocking(block bool) *RingBuffer {
	r.block = block
	if block {
		r.readCond = sync.NewCond(&r.mu)
		r.writeCond = sync.NewCond(&r.mu)
	}
	return r
}

  }

  /**
   * Guaranteed to throw an exception and leave the set unmodified.
   *
   * @since 12.0
   * @throws UnsupportedOperationException always
   * @deprecated Unsupported operation.
   */
  @CanIgnoreReturnValue
  @Deprecated
  @GwtIncompatible // NavigableSet
  @Override
  @DoNotCall("Always throws UnsupportedOperationException")
  public final @Nullable E pollFirst() {