///

这里我们在你的 Pydantic `Settings` 类中定义配置项 `env_file`，并将其设置为我们想要使用的 dotenv 文件名。

### 使用 `lru_cache` 仅创建一次 `Settings` { #creating-the-settings-only-once-with-lru-cache }

从磁盘读取文件通常是一个代价较高（缓慢）的操作，所以你可能希望只在第一次读取，然后复用同一个设置对象，而不是为每个请求都重新读取。

但是，每次我们执行：

```Python
Settings()
```

都会创建一个新的 `Settings` 对象，并且在创建时会再次读取 `.env` 文件。

如果依赖项函数是这样的：

///

ここでは、Pydantic の `Settings` クラス内で設定 `env_file` を定義し、使用したい dotenv ファイルのファイル名を指定しています。

### `lru_cache` で `Settings` を一度だけ作成 { #creating-the-settings-only-once-with-lru-cache }

ディスクからファイルを読むのは通常コスト（遅延）が高い処理なので、1回だけ実行して同じ設定オブジェクトを再利用し、各リクエストごとに読み直さないのが望ましいです。

しかし、次のようにするたびに:

```Python
Settings()
```

///

在這裡我們在 Pydantic 的 `Settings` 類別中定義設定 `env_file`，並將其值設為要使用的 dotenv 檔名。

### 使用 `lru_cache` 只建立一次 `Settings` { #creating-the-settings-only-once-with-lru-cache }

從磁碟讀取檔案通常是昂貴（慢）的操作，所以你可能希望只做一次，然後重複使用同一個設定物件，而不是在每個請求都讀取。

但每次我們這樣做：

```Python
Settings()
```

都會建立一個新的 `Settings` 物件，而且在建立時會再次讀取 `.env` 檔。

如果相依函式只是像這樣：

        // Check for no duplicates
        long tag2Count = Arrays.stream(merged.getTags()).filter(t -> t.equals("tag2")).count();
        assertEquals("tag2 should appear only once", 1, tag2Count);
    }

    @Test
    public void test_merge_allKinds() {
        String[] text1 = { "test" };
        String[][] readings1 = { { "test" } };

   * Returns an immutable <i>view</i> of this array's values as a {@code List}; note that {@code
   * long} values are boxed into {@link Long} instances on demand, which can be very expensive. The
   * returned list should be used once and discarded. For any usages beyond that, pass the returned
   * list to {@link com.google.common.collect.ImmutableList#copyOf(Collection) ImmutableList.copyOf}
   * and use that list instead.
   */

   * default rounding mode: if the two nearest representable values are equally near, the one with
   * the least significant bit zero is chosen. (In such cases, both of the nearest representable
   * values are even integers; this method returns the one that is a multiple of a greater power of
   * two.)
   *

    /**
     * Use a exclusive connection for this tree
     *
     * If an exclusive connection is used the caller must make sure that the tree handle is kept alive,
     * otherwise the connection will be disconnected once the usage drops to zero.
     *
     * @param np
     *            whether to use an exclusive connection
     */
    void setNonPooled(final boolean np) {
        this.nonPooled = np;
    }

    /**

    this.valueSetCapacity = valueSetCapacity;
  }

  /**
   * {@inheritDoc}
   *
   * <p>Creates an empty {@code LinkedHashSet} for a collection of values for one key.
   *
   * @return a new {@code LinkedHashSet} containing a collection of values for one key
   */
  @Override
  Set<V> createCollection() {
    return Platform.newLinkedHashSetWithExpectedSize(valueSetCapacity);
  }

  /**
   * {@inheritDoc}

 *   <li>The {@code copyOf} methods will sometimes recognize that the actual copy operation is
 *       unnecessary; for example, {@code copyOf(copyOf(anArrayList))} should copy the data only
 *       once. This reduces the expense of habitually making defensive copies at API boundaries.
 *       However, the precise conditions for skipping the copy operation are undefined.

   *   <li>The visible constructor or visible static factory method with the most parameters is used
   *       to construct the sample instances. In case of tie, the candidate constructors or
   *       factories are tried one after another until one can be used to construct sample
   *       instances.
   *   <li>For the constructor or static factory method used to construct instances, it's checked