### Einen Callback-`APIRouter` erstellen

Erstellen Sie zunächst einen neuen `APIRouter`, der einen oder mehrere Callbacks enthält.

```Python hl_lines="3  25"
{!../../../docs_src/openapi_callbacks/tutorial001.py!}
```

### Die Callback-*Pfadoperation* erstellen

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:

```Python hl_lines="35"
{!../../../docs_src/openapi_callbacks/tutorial001.py!}
```

!!! tip

⚫️ 🔜 ✔️ *➡ 🛠️* 👈 🔜 📨 `Invoice` 💪, & 🔢 🔢 `callback_url` 👈 🔜 🔌 📛 ⏲.

👉 🍕 📶 😐, 🌅 📟 🎲 ⏪ 😰 👆:

```Python hl_lines="9-13  36-53"
{!../../../docs_src/openapi_callbacks/tutorial001.py!}
```

!!! tip
     `callback_url` 🔢 🔢 ⚙️ Pydantic <a href="https://docs.pydantic.dev/latest/concepts/types/#urls" class="external-link" target="_blank">📛</a> 🆎.

🕴 🆕 👜 `callbacks=messages_callback_router.routes` ❌ *➡ 🛠️ 👨‍🎨*. 👥 🔜 👀 ⚫️❔ 👈 ⏭.

### 添加回调路由

至此，在上文创建的回调路由里就包含了*回调路径操作*（外部开发者要在外部 API 中实现）。

现在使用 API *路径操作装饰器*的参数 `callbacks`，从回调路由传递属性 `.routes`（实际上只是路由/路径操作的**列表**）：

```Python hl_lines="36"
{!../../../docs_src/openapi_callbacks/tutorial001.py!}
```

!!! tip "提示"

    注意，不能把路由本身（`invoices_callback_router`）传递给 `callback=`，要传递 `invoices_callback_router.routes` 中的 `.routes` 属性。

### 查看文档

      |
      """.trimMargin(),
    )
    assertThat(callbacks).isEmpty()
  }

  private fun consumeEvents(source: String) {
    val callback: ServerSentEventReader.Callback =
      object : ServerSentEventReader.Callback {
        override fun onEvent(
          id: String?,
          type: String?,
          data: String,
        ) {
          callbacks.add(Event(id, type, data))
        }

  override fun handle(callbacks: Array<Callback>) {
    for (callback in callbacks) {
      if (callback is PasswordCallback) {
        val console = System.console()

        if (console != null) {
          callback.password = console.readPassword(callback.prompt)
        } else {
          System.err.println(callback.prompt)

     *
     * Use this API to attach timing, debugging, or other application data to a request so that
     * you may read it in interceptors, event listeners, or callbacks.
     */
    @JvmName("reifiedTag")
    inline fun <reified T : Any> tag(tag: T?): Builder = tag(T::class, tag)

    /**

import okio.BufferedSource

/**
 * [HTTP/2][Protocol.HTTP_2] only. Processes server-initiated HTTP requests on the client.
 * Implementations must quickly dispatch callbacks to avoid creating a bottleneck.
 *
 * While [onReset] may occur at any time, the following callbacks are expected in order,
 * correlated by stream ID.
 *
 *  * [onRequest]
 *  * [onHeaders] (unless canceled)
 *  * [onData] (optional sequence of data frames)
 *

import okhttp3.Call
import okhttp3.Callback
import okhttp3.Request
import okhttp3.Response
import okhttp3.ResponseBody
import okhttp3.internal.stripBody
import okhttp3.sse.EventSource
import okhttp3.sse.EventSourceListener

internal class RealEventSource(
  private val request: Request,
  private val listener: EventSourceListener,
) : EventSource, ServerSentEventReader.Callback, Callback {
  private var call: Call? = null

configured to fall back for broad connectivity.

Using OkHttp is easy. Its request/response API is designed with fluent builders and immutability. It
supports both synchronous blocking calls and async calls with callbacks.


Get a URL
---------

This program downloads a URL and prints its contents as a string. [Full source][get_example].

```java
OkHttpClient client = new OkHttpClient();