# 查询参数和字符串校验 { #query-parameters-and-string-validations }

**FastAPI** 允许你为参数声明额外的信息和校验。

让我们以下面的应用为例：

{* ../../docs_src/query_params_str_validations/tutorial001_py310.py hl[7] *}

查询参数 `q` 的类型为 `str | None`，这意味着它是 `str` 类型，但也可以是 `None`。其默认值确实为 `None`，所以 FastAPI 会知道它不是必填的。

/// note | 注意

FastAPI 会因为默认值 `= None` 而知道 `q` 的值不是必填的。

将类型标注为 `str | None` 能让你的编辑器提供更好的辅助和错误检测。

///

## 额外校验 { #additional-validation }

            f.set(c, val);
        } catch (Exception e) {
            throw new AssertionError(e);
        }
    }

    // Helper to build a minimal smb URL
    private static URL smbUrl(String spec) throws Exception {
        return new URL(null, spec, new Handler());
    }

    @Test
    @DisplayName("getConfig returns context config")
    void getConfig_returnsConfig() {

Environment variable'ları anlamak için [Ortam Değişkenleri](../environment-variables.md) dokümanını okuyabilirsiniz.

///

## Tipler ve doğrulama { #types-and-validation }

Bu environment variable'lar yalnızca metin (string) taşıyabilir; çünkü Python'ın dışındadırlar ve diğer programlarla ve sistemin geri kalanıyla uyumlu olmaları gerekir (hatta Linux, Windows, macOS gibi farklı işletim sistemleriyle de).

          && totalLoadTime == other.totalLoadTime
          && evictionCount == other.evictionCount;
    }
    return false;
  }

  @Override
  public String toString() {
    return MoreObjects.toStringHelper(this)
        .add("hitCount", hitCount)
        .add("missCount", missCount)
        .add("loadSuccessCount", loadSuccessCount)

    if (o instanceof RangeMap) {
      RangeMap<?, ?> rangeMap = (RangeMap<?, ?>) o;
      return asMapOfRanges().equals(rangeMap.asMapOfRanges());
    }
    return false;
  }

  @Override
  public String toString() {
    return asMapOfRanges().toString();
  }

  /**
   * This class is used to serialize ImmutableRangeMap instances. Serializes the {@link
   * #asMapOfRanges()} form.
   */

          && totalLoadTime == other.totalLoadTime
          && evictionCount == other.evictionCount;
    }
    return false;
  }

  @Override
  public String toString() {
    return MoreObjects.toStringHelper(this)
        .add("hitCount", hitCount)
        .add("missCount", missCount)
        .add("loadSuccessCount", loadSuccessCount)

            "type": "type_error.integer"
        }
    ]
}
```

你將會改而得到文字版：

```
Validation errors:
Field: ('path', 'item_id'), Error: Input should be a valid integer, unable to parse string as an integer
```

### 覆寫 `HTTPException` 的錯誤處理器 { #override-the-httpexception-error-handler }

同樣地，你也可以覆寫 `HTTPException` 的處理器。

例如，你可能想在這些錯誤時回傳純文字而非 JSON：

            return this; // For simplicity, return self
        }

        @Override
        public void enc_ndr_string(String s) {
            // Simulate encoding a string
            offset += (s.length() * 2) + 4; // Length + null terminator + actual string
        }
    }

    // Test for LsarQosInfo
    @Test
    void testLsarQosInfoEncode() throws NdrException {

 * HashCode} when finished using {@link Hasher#hash}. (See an {@linkplain #newHasher example} of
 * this.)
 *
 * <p>If all you want to hash is a single byte array, string or {@code long} value, there are
 * convenient shortcut methods defined directly on {@link HashFunction} to make this easier.
 *
 * <p>Hasher accepts primitive data types, but can also accept any Object of type {@code T} provided

   */
  @Override
  public int hashCode() {
    return Objects.hash(xStats, yStats, sumOfProductsOfDeltas);
  }

  @Override
  public String toString() {
    if (count() > 0) {
      return MoreObjects.toStringHelper(this)
          .add("xStats", xStats)
          .add("yStats", yStats)
          .add("populationCovariance", populationCovariance())