批量请求

本文档介绍了如何对 API 调用进行批处理以减少客户端必须建立的 HTTP 连接数量。

本文档专门介绍了如何通过发送 HTTP 请求来发出批处理请求。如果您要使用某个 Google 客户端库来发出批处理请求，请参阅该客户端库的说明文档。

概览

客户端建立的每个 HTTP 连接都会产生一定的开销。Google Classroom API 支持批处理，这样您的客户端就可以将多个 API 调用组合为一个 HTTP 请求。

在以下示例情况下，您可能需要使用批处理：

• 检索大量课程的学生名单。
• 批量创建或更新课程。
• 添加大量课程名单。
• 检索大量用户的课程列表。

在上述每种情况下，您都可以将这些调用组合成一个 HTTP 请求，而不是单独发送每个调用。请注意，所有内部请求都必须发送到同一 Google API。

单个批量请求最多可以包含 50 次调用。如果必须进行更多调用，请使用多个批量请求。

注意：Google Classroom API 的批处理系统使用的语法与 OData 批处理系统相同，但语义有所不同。

批量详情

批量请求就是将多个 API 调用进行合并而形成的一个 HTTP 请求，您可以将此请求发送到 API 发现文档中指定的 batchPath。默认路径为 /batch/api_name/api_version。本部分详细介绍了批处理语法，随后还会提供一个示例。

注意：一组一起进行批处理的 n 个请求将按 n 个请求（而非一个请求）计入用量限额。在处理之前，系统会将批量请求拆分为一组请求。

批量请求的格式

批量请求是一个包含多个 Google Classroom API 调用的标准 HTTP 请求，使用 multipart/mixed 内容类型。在此主 HTTP 请求中，每个部分都包含一个内嵌的 HTTP 请求。

各个部分都以其自身的 Content-Type: application/http 标头开头。您还可以选择添加一个 Content-ID 标头。不过，每个部分的标头仅用于标记该部分的开头，而与嵌套请求无关。在服务器将批量请求拆分为多个单独请求之后，每个部分的标头就会被忽略。

各个部分的正文是一个完整的 HTTP 请求，各自有专用的动词、网址、标头和正文。此 HTTP 请求必须仅包含网址的路径部分；不允许在批量请求中使用完整的网址。

外部批量请求的 HTTP 标头应用于批次中的每个请求，但 Content-Type 之类的 Content- 标头除外。如果您在外部请求和个别调用中都指定了特定的 HTTP 标头，则个别调用标头的值将替换外部批量请求标头的值。另请注意，单个调用的标头仅应用于该调用本身。

例如，如果您为特定调用提供了 Authorization 标头，则该标头仅应用于该调用。如果您为外部请求提供了 Authorization 标头，则该标头将应用于所有的单个调用，除非单个调用将其替换为自身的 Authorization 标头。

当服务器收到批处理请求时，会将外部请求的查询参数和标头（如果适用）应用于各部分，然后将各部分视作单独的 HTTP 请求进行处理。

对批量请求的响应

服务器的响应是一个标准的 HTTP 响应，使用 multipart/mixed 内容类型；其中的每个部分分别是对批量请求中一个请求的响应，且顺序与这些请求相同。

和请求中的各部分一样，响应中的各部分都包含一个完整的 HTTP 响应，其中包括状态代码、标头和正文。此外，和请求中的各部分一样，响应中的各部分均以 Content-Type 标头为前缀，用于标记各部分的开头。

如果请求的某个特定部分具有 Content-ID 标头，则响应的对应部分也会有相同的 Content-ID 标头，其格式为在原始值前面加上 response- 字符串，如下例所示。

注意：服务器可能会以任何顺序执行您的调用，因此不要预期这些调用将会以您指定的顺序执行。如果要确保两个调用以指定顺序执行，就不能在单个请求中发送这两个调用。正确的做法是，先单独发送第一个调用，等收到其响应之后再发送第二个。

示例

以下示例展示了如何将批处理与 Google Classroom API 结合使用。

批量请求示例

POST https://classroom.googleapis.com/batch HTTP/1.1
Authorization: Bearer your_auth_token
Content-Type: multipart/mixed; boundary=batch_foobarbaz
Content-Length: total_content_length

--batch_foobarbaz
Content-Type: application/http
Content-Transfer-Encoding: binary
MIME-Version: 1.0
Content-ID: <item1:[e-mail]>

PATCH /v1/courses/134529639?updateMask=name HTTP/1.1
Content-Type: application/json; charset=UTF-8
Authorization: Bearer your_auth_token

{
  "name": "Course 1"
}
--batch_foobarbaz
Content-Type: application/http
Content-Transfer-Encoding: binary
MIME-Version: 1.0
Content-ID: <item2:[e-mail]>

PATCH /v1/courses/134529901?updateMask=section HTTP/1.1
Content-Type: application/json; charset=UTF-8
Authorization: Bearer your_auth_token
{
  "section": "Section 2"
}
--batch_foobarbaz--

批量响应示例

此部分是对上一部分中的示例请求的响应。

HTTP/1.1 200
Content-Length: response_total_content_length
Content-Type: multipart/mixed; boundary=batch_foobarbaz

--batch_foobarbaz
Content-Type: application/http
Content-ID: <response-item1:[e-mail]>

HTTP/1.1 200 OK
Content-Type application/json
Content-Length: response_part_1_content_length

{
  "id": "134529639",
  "name": "Course 1",
  "section": "Section 1",
  "ownerId": "116269102540619633451",
  "creationTime": "2015-06-25T14:23:56.535Z",
  "updateTime": "2015-06-25T14:33:06.583Z",
  "enrollmentCode": "6paeflo",
  "courseState": "PROVISIONED",
  "alternateLink": "http://classroom.google.com/c/MTM0NTI5NjM5"
}
--batch_foobarbaz
Content-Type: application/http
Content-ID: <response-item2:[e-mail]>

HTTP/1.1 200 OK
Content-Type: application/json
Content-Length: response_part_2_content_length

{
  "id": "134529901",
  "name": "Course 1",
  "section": "Section 2",
  "ownerId": "116269102540619633451",
  "creationTime": "2015-06-25T14:23:08.761Z",
  "updateTime": "2015-06-25T14:33:06.490Z",
  "enrollmentCode": "so75ha5",
  "courseState": "PROVISIONED",
  "alternateLink": "http://classroom.google.com/c/MTM0NTI5OTAx"
}
--batch_foobarbaz--

使用客户端库

以下代码示例演示了如何使用 Google API 客户端库发出批量请求。如需详细了解如何安装和设置这些库，请参阅相应的快速入门指南。

.NET

classroom/snippets/ClassroomSnippets/BatchAddStudents.cs

在 GitHub 上查看

using Google;
using Google.Apis.Auth.OAuth2;
using Google.Apis.Classroom.v1;
using Google.Apis.Classroom.v1.Data;
using Google.Apis.Requests;
using Google.Apis.Services;
using System;
using System.Collections.Generic;
using System.Threading.Tasks;

namespace ClassroomSnippets
{
    // Class to demonstrate the use of Classroom Batch Add Students API
    public class BatchAddStudents
    {
        /// <summary>
        /// Add multiple students in a specified course.
        /// </summary>
        /// <param name="courseId">Id of the course to add students.</param>
        /// <param name="studentEmails">Email address of the students.</param>
        public static void ClassroomBatchAddStudents(string courseId,
            List<string> studentEmails)
        {
            try
            {
                /* Load pre-authorized user credentials from the environment.
                 TODO(developer) - See https://developers.google.com/identity for 
                 guides on implementing OAuth2 for your application. */
                GoogleCredential credential = GoogleCredential.GetApplicationDefault()
                    .CreateScoped(ClassroomService.Scope.ClassroomRosters);

                // Create Classroom API service.
                var service = new ClassroomService(new BaseClientService.Initializer
                {
                    HttpClientInitializer = credential,
                    ApplicationName = "Classroom Snippets"
                });

                var batch = new BatchRequest(service, "https://classroom.googleapis.com/batch");
                BatchRequest.OnResponse<Student> callback = (student, error, i, message) =>
                {
                    if (error != null)
                    {
                        Console.WriteLine("Error adding student to the course: {0}", error.Message);
                    }
                    else
                    {
                        Console.WriteLine("User '{0}' was added as a student to the course.",
                            student.Profile.Name.FullName);
                    }
                };
                foreach (var studentEmail in studentEmails)
                {
                    var student = new Student() {UserId = studentEmail};
                    var request = service.Courses.Students.Create(student, courseId);
                    batch.Queue<Student>(request, callback);
                }

                Task.WaitAll(batch.ExecuteAsync());
            }
            catch (Exception e)
            {
                // TODO(developer) - handle error appropriately
                if (e is AggregateException)
                {
                    Console.WriteLine("Credential Not found");
                }
                else if (e is GoogleApiException)
                {
                    Console.WriteLine("Course does not exist.");
                }
                else
                {
                    throw;
                }
            }
        }
    }
}

Java

classroom/snippets/src/main/java/BatchAddStudents.java

在 GitHub 上查看

import com.google.api.client.googleapis.batch.BatchRequest;
import com.google.api.client.googleapis.batch.json.JsonBatchCallback;
import com.google.api.client.googleapis.javanet.GoogleNetHttpTransport;
import com.google.api.client.googleapis.json.GoogleJsonError;
import com.google.api.client.http.HttpHeaders;
import com.google.api.client.http.javanet.NetHttpTransport;
import com.google.api.client.json.gson.GsonFactory;
import com.google.api.services.classroom.Classroom;
import com.google.api.services.classroom.ClassroomScopes;
import com.google.api.services.classroom.model.Student;
import java.io.IOException;
import java.security.GeneralSecurityException;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;

/* Class to demonstrate the use of Classroom Batch Add Students API */
public class BatchAddStudents {

  /* Scopes required by this API call. If modifying these scopes, delete your previously saved
  tokens/ folder. */
  static ArrayList<String> SCOPES =
      new ArrayList<>(Arrays.asList(ClassroomScopes.CLASSROOM_ROSTERS));

  /**
   * Add multiple students in a specified course.
   *
   * @param courseId - Id of the course to add students.
   * @param studentEmails - Email address of the students.
   * @throws IOException - if credentials file not found.
   * @throws GeneralSecurityException - if a new instance of NetHttpTransport was not created.
   */
  public static void batchAddStudents(String courseId, List<String> studentEmails)
      throws GeneralSecurityException, IOException {

    // Create the classroom API client.
    final NetHttpTransport HTTP_TRANSPORT = GoogleNetHttpTransport.newTrustedTransport();
    Classroom service =
        new Classroom.Builder(
                HTTP_TRANSPORT,
                GsonFactory.getDefaultInstance(),
                ClassroomCredentials.getCredentials(HTTP_TRANSPORT, SCOPES))
            .setApplicationName("Classroom samples")
            .build();

    BatchRequest batch = service.batch();
    JsonBatchCallback<Student> callback =
        new JsonBatchCallback<>() {
          public void onSuccess(Student student, HttpHeaders responseHeaders) {
            System.out.printf(
                "User '%s' was added as a student to the course.\n",
                student.getProfile().getName().getFullName());
          }

          public void onFailure(GoogleJsonError error, HttpHeaders responseHeaders) {
            System.out.printf("Error adding student to the course: %s\n", error.getMessage());
          }
        };
    for (String studentEmail : studentEmails) {
      Student student = new Student().setUserId(studentEmail);
      service.courses().students().create(courseId, student).queue(batch, callback);
    }
    batch.execute();
  }
}

PHP

classroom/snippets/src/ClassroomBatchAddStudents.php

在 GitHub 上查看

use Google\Client;
use Google\Service\Classroom;
use Google\Service\Classroom\Student;
use Google\Service\Exception;

function batchAddStudents($courseId, $studentEmails)
{
    /* Load pre-authorized user credentials from the environment.
    TODO(developer) - See https://developers.google.com/identity for
     guides on implementing OAuth2 for your application. */
    $client = new Client();
    $client->useApplicationDefaultCredentials();
    $client->addScope("https://www.googleapis.com/auth/classroom.profile.emails");
    $service = new Classroom($client);
    $service->getClient()->setUseBatch(true);
    //create batch
    $batch = $service->createBatch();
    foreach ($studentEmails as $studentEmail) {
        $student = new Student([
            'userId' => $studentEmail
        ]);
        $request = $service->courses_students->create($courseId, $student);
        $requestId = $studentEmail;
        $batch->add($request, $requestId);
    }
    //executing request
    $results = $batch->execute();
    foreach ($results as $responseId => $student) {
        $studentEmail = substr($responseId, strlen('response-') + 1);
        if ($student instanceof Exception) {
            $e = $student;
            printf("Error adding user '%s' to the course: %s\n", $studentEmail,
                $e->getMessage());
        } else {
            printf("User '%s' was added as a student to the course.\n",
                $student->profile->name->fullName, $courseId);
        }
    }
    $service->getClient()->setUseBatch(false);
    return $results;
}

Python

course_id = '123456'
student_emails = ['[e-mail]', '[e-mail]']
def callback(request_id, response, exception):
    if exception is not None:
        print 'Error adding user "{0}" to the course course: {1}'.format(
            request_id, exception)
    else:
        print 'User "{0}" added as a student to the course.'.format(
            response.get('profile').get('name').get('fullName'))
batch = service.new_batch_http_request(callback=callback)
for student_email in student_emails:
    student = {
        'userId': student_email
    }
    request = service.courses().students().create(courseId=course_id,
                                                  body=student)
    batch.add(request, request_id=student_email)
batch.execute(http=http)