super();
    }

    // ===================================================================================
    //                                                                           Attribute
    //                                                                           =========
    /** Helper for crawling configuration management. */
    @Resource
    protected CrawlingConfigHelper crawlingConfigHelper;

    // ===================================================================================
    //                                                                           Attribute
    //                                                                           =========
    @Resource
    protected FessConfig fessConfig;

    private static final long serialVersionUID = 1L;

    // ===================================================================================
    //                                                                           Attribute
    //                                                                           =========
    protected DocMeta docMeta;
    protected final EntityUniqueDrivenProperties __uniqueDrivenProperties = newUniqueDrivenProperties();

    //

    // ===================================================================================
    //                                                                           Attribute
    //

    // ===================================================================================
    //                                                                         Constructor

Now use the parameter `callbacks` in *your API's path operation decorator* to pass the attribute `.routes` (that's actually just a `list` of routes/*path operations*) from that callback router:

{* ../../docs_src/openapi_callbacks/tutorial001.py hl[35] *}

/// tip

Notice that you are not passing the router itself (`invoices_callback_router`) to `callback=`, but the attribute `.routes`, as in `invoices_callback_router.routes`.

///

You can reuse FastAPI's internal functions to create the HTML pages for the docs, and pass them the needed arguments:

* `openapi_url`: the URL where the HTML page for the docs can get the OpenAPI schema for your API. You can use here the attribute `app.openapi_url`.
* `title`: the title of your API.
* `oauth2_redirect_url`: you can use `app.swagger_ui_oauth2_redirect_url` here to use the default.

{* ../../docs_src/openapi_callbacks/tutorial001.py hl[35] *}

/// tip | Tipp

Beachten Sie, dass Sie nicht den Router selbst (`invoices_callback_router`) an `callback=` übergeben, sondern das Attribut `.routes`, wie in `invoices_callback_router.routes`.

///

    // ===================================================================================
    //                                                                           Attribute
    //                                                                           =========
    protected List<AbstractAggregationBuilder<?>> aggregationAggregationBuilderList;

     * The module name is extracted from the {@code module-info.class} file if present, otherwise from
     * the {@code "Automatic-Module-Name"} attribute of the {@code META-INF/MANIFEST.MF} file if present.
     *
     * <p>A typical usage is to invoke this method for all dependencies having a
     * {@link DependencyScope#TEST TEST} or {@link DependencyScope#TEST_ONLY TEST_ONLY}

        super();
    }

    // ===================================================================================
    //                                                                           Attribute
    //                                                                           =========
    /** System properties for dynamic configuration management */
    @Resource
    protected DynamicProperties systemProperties;