# 路徑參數與數值驗證 { #path-parameters-and-numeric-validations }

就像使用 `Query` 為查詢參數宣告更多驗證與中繼資料一樣，你也可以用 `Path` 為路徑參數宣告相同類型的驗證與中繼資料。

## 匯入 `Path` { #import-path }

首先，從 `fastapi` 匯入 `Path`，並匯入 `Annotated`：

{* ../../docs_src/path_params_numeric_validations/tutorial001_an_py310.py hl[1,3] *}

/// info

FastAPI 在 0.95.0 版加入並開始推薦使用 `Annotated`。

如果你使用更舊的版本，嘗試使用 `Annotated` 會出錯。

{
    "openapi": "3.1.0",
    "info": {
        "title": "FastAPI",
        "version": "0.1.0"
    },
    "paths": {
        "/items/": {
            "get": {
                "summary": "Read Items",
                "operationId": "read_items_items__get",
                "responses": {
                    "200": {
                        "description": "Successful Response",
                        "content": {

                path = path + formatter.getFileExtension();
            }

            if (path.startsWith("/")) {
                path = path.substring(1);
            }

            final String[] components = (host + "/" + path).split("/");
            final StringBuilder sanitized = new StringBuilder();
            for (int i = 0; i < components.length; i++) {

Bu, tüm API'nızı oluşturmak için ana etkileşim noktası olacaktır.

### Adım 3: bir *path operation* oluşturun { #step-3-create-a-path-operation }

#### Path { #path }

Buradaki "Path", URL'in ilk `/` işaretinden başlayarak son kısmını ifade eder.

Yani, şu şekilde bir URL'de:

```
https://example.com/items/foo
```

...path şöyle olur:

```
/items/foo
```

/// info | Bilgi

     *
     * @param artifact the artifact for which to associate a path
     * @param path path to associate to the given artifact
     *
     * @see org.apache.maven.api.services.ArtifactManager#setPath(ProducedArtifact, Path)
     */
    void setArtifactPath(@Nonnull ProducedArtifact artifact, @Nonnull Path path);

    /**
     * Shortcut for {@code getService(ArtifactManager.class).getPath(...)}.

#     <type> <name>
#
# Type can be:
#    path - an exact path to a single file
#    file-name - an exact leaf filename, regardless of path
#    path-prefix - a prefix match on the file path
#    file-prefix - a prefix match of the leaf filename (no path)
#    paths-from-repo - read a file from the repo and load file paths
#

file-prefix	zz_generated.

file-name	types.generated.go

    /**
     * Default constructor.
     */
    public SearchBody() {
        super();
    }

    /** Name of the file crawling configuration */
    public String name;

    /** File paths to crawl */
    public String paths;

    /** Description of the file crawling configuration */
    public String description;

        }

        public boolean parsingFailed = false;
        public Path cwd;
        public Path installationDirectory;
        public Path userHomeDirectory;
        public Map<String, String> systemProperties;
        public Map<String, String> userProperties;
        public Path topDirectory;

        @Nullable
        public Path rootDirectory;

        @Nullable
        public List<CoreExtensions> extensions;

    /** The path of the HTML: /admin/pathmap/admin_pathmap.jsp */
    HtmlNext path_AdminPathmap_AdminPathmapJsp = new HtmlNext("/admin/pathmap/admin_pathmap.jsp");

    /** The path of the HTML: /admin/pathmap/admin_pathmap_details.jsp */
    HtmlNext path_AdminPathmap_AdminPathmapDetailsJsp = new HtmlNext("/admin/pathmap/admin_pathmap_details.jsp");

    /** The path of the HTML: /admin/pathmap/admin_pathmap_edit.jsp */

    client = TestClient(app)
    response = client.get(path, headers={"p": "hello"})
    assert response.status_code == 200
    assert response.json() == {"p": None}


@pytest.mark.parametrize(
    "path",
    [
        "/optional-alias",
        "/model-optional-alias",
    ],
)
def test_optional_alias_by_alias(path: str):
    client = TestClient(app)