2. By using a `with` block, we make sure that the file-like object is closed after the generator function is done. So, after it finishes sending the response.
3. This `yield from` tells the function to iterate over that thing named `file_like`. And then, for each part iterated, yield that part as coming from this generator function (`iterfile`).

    So, it is a generator function that transfers the "generating" work to something else internally.

    private Map<String, MavenProject> projectMap;

    /**
     * Sort a list of projects.
     * <ul>
     * <li>collect all the vertices for the projects that we want to build.</li>
     * <li>iterate through the deps of each project and if that dep is within
     * the set of projects we want to build then add an edge, otherwise throw
     * the edge away because that dependency is not within the set of projects

 * Multiset#entrySet()} method, plus optionally overriding {@link #add(Object, int)} and {@link
 * #remove(Object, int)} to enable modifications to the multiset.
 *
 * <p>The {@link #count} and {@link #size} implementations all iterate across the set returned by
 * {@link Multiset#entrySet()}, as do many methods acting on the set returned by {@link
 * #elementSet()}. Override those methods for better performance.
 *
 * @author Kevin Bourrillion

 * <p>The collections returned by {@link #keySet()} and {@link #asMap()} iterate through the keys in
 * the order they were first added to the multimap. Similarly, {@link #get}, {@link #removeAll}, and
 * {@link #replaceValues} return collections that iterate through the values in the order they were
 * added. The collections generated by {@link #entries()}, {@link #keys()}, and {@link #values}

비동기 제너레이터 또는 일반 제너레이터/이터레이터를 받아 응답 본문을 스트리밍 합니다.

{* ../../docs_src/custom_response/tutorial007.py hl[2,14] *}

#### 파일과 같은 객체를 사용한 `StreamingResponse`

파일과 같은 객체(예: `open()`으로 반환된 객체)가 있는 경우, 해당 파일과 같은 객체를 반복(iterate)하는 제너레이터 함수를 만들 수 있습니다.

이 방식으로, 파일 전체를 메모리에 먼저 읽어들일 필요 없이, 제너레이터 함수를 `StreamingResponse`에 전달하여 반환할 수 있습니다.

이 방식은 클라우드 스토리지, 비디오 처리 등의 다양한 라이브러리와 함께 사용할 수 있습니다.

import org.opensearch.transport.client.Client;

/**
 * <p>
 * {@link ESSourceReader} reads documents from Elasticsearch using the scroll API.
 * It implements the {@link DocumentReader} interface to provide a way to iterate over documents
 * in a large index without loading all of them into memory at once.
 * </p>
 *
 * <p>
 * The reader supports limiting the number of documents read based on a percentage of the total documents

                assertTrue(urlQueue.getUrl().startsWith(url2));
            }

            dataService.iterate(sessionId1, accessResult -> {
                assertTrue(accessResult.getUrl().startsWith(url1));
                assertEquals(Constants.GET_METHOD, accessResult.getMethod());
            });
            dataService.iterate(sessionId2, accessResult -> {
                assertTrue(accessResult.getUrl().startsWith(url2));

    // is likely to be a bug anyway.

    // N.B. All writes to the list and the next pointers must have happened before the above
    // synchronized block, so we can iterate the list without the lock held here.
    RunnableExecutorPair reversedList = null;
    while (list != null) {
      RunnableExecutorPair tmp = list;
      list = list.next;
      tmp.next = reversedList;

   * Dispatches all events enqueued prior to this call, serially and in order, for every listener.
   *
   * <p>Note: this method is idempotent and safe to call from any thread
   */
  public void dispatch() {
    // iterate by index to avoid concurrent modification exceptions
    for (int i = 0; i < listeners.size(); i++) {
      listeners.get(i).dispatch();
    }
  }

  /**

   * Dispatches all events enqueued prior to this call, serially and in order, for every listener.
   *
   * <p>Note: this method is idempotent and safe to call from any thread
   */
  public void dispatch() {
    // iterate by index to avoid concurrent modification exceptions
    for (int i = 0; i < listeners.size(); i++) {
      listeners.get(i).dispatch();
    }
  }

  /**