```
https://yourapi.com/invoices/?callback_url=https://www.external.org/events
```

並附上這個 JSON body：

```JSON
{
    "id": "2expen51ve",
    "customer": "Mr. Richie Rich",
    "total": "9999"
}
```

那麼「你的 API」會處理這張發票，並在稍後某個時點，向 `callback_url`（也就是「外部 API」）送出回呼請求：

```
https://www.external.org/events/invoices/2expen51ve
```

其 JSON body 大致包含：

```JSON
{

{* ../../docs_src/stream_json_lines/tutorial001_py310.py ln[33:36] hl[34] *}

## 服务器发送事件（SSE） { #server-sent-events-sse }

 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.google.common.eventbus.outside;

import static com.google.common.truth.Truth.assertThat;

import com.google.common.eventbus.Subscribe;
import com.google.common.eventbus.outside.AnnotatedNotAbstractInSuperclassTest.SubClass;
import java.util.ArrayList;
import java.util.List;

import okio.ByteString.Companion.toByteString

/**
 * Logs SSL keys to a log file, allowing Wireshark to decode traffic and be examined with http2
 * filter. The approach is to hook into JSSE log events for the messages between client and server
 * during handshake, and then take the agreed masterSecret from private fields of the session.
 *
 * Copy WireSharkKeyLoggerListener to your test code to use in development.
 *

import gradlebuild.AbstractBuildScanInfoCollectingService
import gradlebuild.registerBuildScanInfoCollectingService
import org.gradle.tooling.events.task.TaskOperationResult
import org.gradle.tooling.events.task.TaskSuccessResult
import java.io.Serializable
import java.util.concurrent.atomic.AtomicBoolean

/**

  /**
   * Configure this call to publish all future events to [eventListener], in addition to the
   * listeners configured by [OkHttpClient.Builder.eventListener] and other calls to this function.
   *
   * If this call is later [cloned][clone], [eventListener] will not be notified of its events.
   *
   * There is no mechanism to remove an event listener. Implementations should instead ignore events
   * that they are not interested in.
   *

user  nginx;
worker_processes  auto;

error_log  /var/log/nginx/error.log warn;
pid        /var/run/nginx.pid;

events {
    worker_connections  4096;
}

http {
    include       /etc/nginx/mime.types;
    default_type  application/octet-stream;

    log_format  main  '$remote_addr - $remote_user [$time_local] "$request" '
                      '$status $body_bytes_sent "$http_referer" '

user  nginx;
worker_processes  auto;

error_log  /var/log/nginx/error.log warn;
pid        /var/run/nginx.pid;

events {
    worker_connections  4096;
}

http {
    include       /etc/nginx/mime.types;
    default_type  application/octet-stream;

    log_format  main  '$remote_addr - $remote_user [$time_local] "$request" '
                      '$status $body_bytes_sent "$http_referer" '

@NullUnmarked
public class SubscriberTest extends TestCase {

  private static final Object FIXTURE_ARGUMENT = new Object();

  private EventBus bus;
  private boolean methodCalled;
  private @Nullable Object methodArgument;

  @Override
  protected void setUp() throws Exception {
    bus = new EventBus();
    methodCalled = false;
    methodArgument = null;
  }

  public void testCreate() {

```
https://yourapi.com/invoices/?callback_url=https://www.external.org/events
```

JSON body가 다음과 같다면:

```JSON
{
    "id": "2expen51ve",
    "customer": "Mr. Richie Rich",
    "total": "9999"
}
```

그러면 *여러분의 API*는 청구서를 처리하고, 나중에 어느 시점에서 `callback_url`(즉 *external API*)로 콜백 요청을 보냅니다:

```
https://www.external.org/events/invoices/2expen51ve
```

그리고 다음과 같은 JSON body를 포함할 것입니다: