您可以通过两种方式使用 Gmail API 发送电子邮件:
- 您可以使用
messages.send
方法直接发送。 - 您可以使用
drafts.send
方法从草稿中发送电子邮件。
电子邮件以 base64url 编码的字符串形式在消息资源的 raw
属性中发送。发送电子邮件的总体工作流程如下:
- 以某种便捷的方式创建电子邮件内容,并将其编码为 base64url 字符串。
- 创建新的消息资源,并将其
raw
属性设置为您刚刚创建的 base64url 字符串。 - 调用
messages.send
,或者,如果发送的是草稿,则调用drafts.send
来发送消息。
此工作流程的详细信息可能会因您选择的客户端库和编程语言而异。
创建消息
Gmail API 需要符合 RFC 2822 且编码为 base64url 字符串的 MIME 电子邮件。许多编程语言都有库或实用程序,可简化创建和编码 MIME 消息的过程。以下代码示例演示了如何使用适用于各种语言的 Google API 客户端库创建 MIME 消息。
Java
使用 javax.mail.internet
软件包中的 MimeMessage
类可以大大简化电子邮件消息的创建过程。以下示例展示了如何创建电子邮件,包括邮件头:
import java.util.Properties; import javax.mail.MessagingException; import javax.mail.Session; import javax.mail.internet.InternetAddress; import javax.mail.internet.MimeMessage; /* Class to demonstrate the use of Gmail Create Email API */ public class CreateEmail { /** * Create a MimeMessage using the parameters provided. * * @param toEmailAddress email address of the receiver * @param fromEmailAddress email address of the sender, the mailbox account * @param subject subject of the email * @param bodyText body text of the email * @return the MimeMessage to be used to send email * @throws MessagingException - if a wrongly formatted address is encountered. */ public static MimeMessage createEmail(String toEmailAddress, String fromEmailAddress, String subject, String bodyText) throws MessagingException { Properties props = new Properties(); Session session = Session.getDefaultInstance(props, null); MimeMessage email = new MimeMessage(session); email.setFrom(new InternetAddress(fromEmailAddress)); email.addRecipient(javax.mail.Message.RecipientType.TO, new InternetAddress(toEmailAddress)); email.setSubject(subject); email.setText(bodyText); return email; } }
下一步是对 MimeMessage
进行编码,实例化 Message
对象,并将 base64url 编码的消息字符串设置为 raw
属性的值。
import com.google.api.services.gmail.model.Message; import java.io.ByteArrayOutputStream; import java.io.IOException; import javax.mail.MessagingException; import javax.mail.internet.MimeMessage; import org.apache.commons.codec.binary.Base64; /* Class to demonstrate the use of Gmail Create Message API */ public class CreateMessage { /** * Create a message from an email. * * @param emailContent Email to be set to raw of message * @return a message containing a base64url encoded email * @throws IOException - if service account credentials file not found. * @throws MessagingException - if a wrongly formatted address is encountered. */ public static Message createMessageWithEmail(MimeMessage emailContent) throws MessagingException, IOException { ByteArrayOutputStream buffer = new ByteArrayOutputStream(); emailContent.writeTo(buffer); byte[] bytes = buffer.toByteArray(); String encodedEmail = Base64.encodeBase64URLSafeString(bytes); Message message = new Message(); message.setRaw(encodedEmail); return message; } }
Python
以下代码示例演示了如何创建 MIME 消息、将其编码为 base64url 字符串,并将其分配给 Message
资源的 raw
字段:
import base64 from email.message import EmailMessage import google.auth from googleapiclient.discovery import build from googleapiclient.errors import HttpError def gmail_create_draft(): """Create and insert a draft email. Print the returned draft's message and id. Returns: Draft object, including draft id and message meta data. Load pre-authorized user credentials from the environment. TODO(developer) - See https://developers.google.com/identity for guides on implementing OAuth2 for the application. """ creds, _ = google.auth.default() try: # create gmail api client service = build("gmail", "v1", credentials=creds) message = EmailMessage() message.set_content("This is automated draft mail") message["To"] = "[email protected]" message["From"] = "[email protected]" message["Subject"] = "Automated draft" # encoded message encoded_message = base64.urlsafe_b64encode(message.as_bytes()).decode() create_message = {"message": {"raw": encoded_message}} # pylint: disable=E1101 draft = ( service.users() .drafts() .create(userId="me", body=create_message) .execute() ) print(f'Draft id: {draft["id"]}\nDraft message: {draft["message"]}') except HttpError as error: print(f"An error occurred: {error}") draft = None return draft if __name__ == "__main__": gmail_create_draft()
创建包含附件的消息
创建含附件的消息与创建任何其他消息类似,但将文件作为多部分 MIME 消息上传的过程取决于编程语言。以下代码示例演示了创建包含附件的多部分 MIME 消息的可能方式。
Java
以下示例展示了如何创建多部分 MIME 消息,编码和分配步骤与上述相同。
import com.google.api.client.googleapis.json.GoogleJsonError; import com.google.api.client.googleapis.json.GoogleJsonResponseException; import com.google.api.client.http.HttpRequestInitializer; import com.google.api.client.http.javanet.NetHttpTransport; import com.google.api.client.json.gson.GsonFactory; import com.google.api.services.gmail.Gmail; import com.google.api.services.gmail.GmailScopes; import com.google.api.services.gmail.model.Draft; import com.google.api.services.gmail.model.Message; import com.google.auth.http.HttpCredentialsAdapter; import com.google.auth.oauth2.GoogleCredentials; import java.io.ByteArrayOutputStream; import java.io.File; import java.io.IOException; import java.util.Properties; import javax.activation.DataHandler; import javax.activation.DataSource; import javax.activation.FileDataSource; import javax.mail.MessagingException; import javax.mail.Multipart; import javax.mail.Session; import javax.mail.internet.InternetAddress; import javax.mail.internet.MimeBodyPart; import javax.mail.internet.MimeMessage; import javax.mail.internet.MimeMultipart; import org.apache.commons.codec.binary.Base64; /* Class to demonstrate the use of Gmail Create Draft with attachment API */ public class CreateDraftWithAttachment { /** * Create a draft email with attachment. * * @param fromEmailAddress - Email address to appear in the from: header. * @param toEmailAddress - Email address of the recipient. * @param file - Path to the file to be attached. * @return the created draft, {@code null} otherwise. * @throws MessagingException - if a wrongly formatted address is encountered. * @throws IOException - if service account credentials file not found. */ public static Draft createDraftMessageWithAttachment(String fromEmailAddress, String toEmailAddress, File file) throws MessagingException, IOException { /* Load pre-authorized user credentials from the environment. TODO(developer) - See https://developers.google.com/identity for guides on implementing OAuth2 for your application.*/ GoogleCredentials credentials = GoogleCredentials.getApplicationDefault() .createScoped(GmailScopes.GMAIL_COMPOSE); HttpRequestInitializer requestInitializer = new HttpCredentialsAdapter(credentials); // Create the gmail API client Gmail service = new Gmail.Builder(new NetHttpTransport(), GsonFactory.getDefaultInstance(), requestInitializer) .setApplicationName("Gmail samples") .build(); // Create the email content String messageSubject = "Test message"; String bodyText = "lorem ipsum."; // Encode as MIME message Properties props = new Properties(); Session session = Session.getDefaultInstance(props, null); MimeMessage email = new MimeMessage(session); email.setFrom(new InternetAddress(fromEmailAddress)); email.addRecipient(javax.mail.Message.RecipientType.TO, new InternetAddress(toEmailAddress)); email.setSubject(messageSubject); MimeBodyPart mimeBodyPart = new MimeBodyPart(); mimeBodyPart.setContent(bodyText, "text/plain"); Multipart multipart = new MimeMultipart(); multipart.addBodyPart(mimeBodyPart); mimeBodyPart = new MimeBodyPart(); DataSource source = new FileDataSource(file); mimeBodyPart.setDataHandler(new DataHandler(source)); mimeBodyPart.setFileName(file.getName()); multipart.addBodyPart(mimeBodyPart); email.setContent(multipart); // Encode and wrap the MIME message into a gmail message ByteArrayOutputStream buffer = new ByteArrayOutputStream(); email.writeTo(buffer); byte[] rawMessageBytes = buffer.toByteArray(); String encodedEmail = Base64.encodeBase64URLSafeString(rawMessageBytes); Message message = new Message(); message.setRaw(encodedEmail); try { // Create the draft message Draft draft = new Draft(); draft.setMessage(message); draft = service.users().drafts().create("me", draft).execute(); System.out.println("Draft id: " + draft.getId()); System.out.println(draft.toPrettyString()); return draft; } catch (GoogleJsonResponseException e) { // TODO(developer) - handle error appropriately GoogleJsonError error = e.getDetails(); if (error.getCode() == 403) { System.err.println("Unable to create draft: " + e.getDetails()); } else { throw e; } } return null; } }
Python
与上一个示例类似,此示例也会处理将消息编码为 base64url 并将其分配给 Message
资源的 raw
字段。
import base64 import mimetypes import os from email.message import EmailMessage from email.mime.audio import MIMEAudio from email.mime.base import MIMEBase from email.mime.image import MIMEImage from email.mime.text import MIMEText import google.auth from googleapiclient.discovery import build from googleapiclient.errors import HttpError def gmail_create_draft_with_attachment(): """Create and insert a draft email with attachment. Print the returned draft's message and id. Returns: Draft object, including draft id and message meta data. Load pre-authorized user credentials from the environment. TODO(developer) - See https://developers.google.com/identity for guides on implementing OAuth2 for the application. """ creds, _ = google.auth.default() try: # create gmail api client service = build("gmail", "v1", credentials=creds) mime_message = EmailMessage() # headers mime_message["To"] = "[email protected]" mime_message["From"] = "[email protected]" mime_message["Subject"] = "sample with attachment" # text mime_message.set_content( "Hi, this is automated mail with attachment.Please do not reply." ) # attachment attachment_filename = "photo.jpg" # guessing the MIME type type_subtype, _ = mimetypes.guess_type(attachment_filename) maintype, subtype = type_subtype.split("/") with open(attachment_filename, "rb") as fp: attachment_data = fp.read() mime_message.add_attachment(attachment_data, maintype, subtype) encoded_message = base64.urlsafe_b64encode(mime_message.as_bytes()).decode() create_draft_request_body = {"message": {"raw": encoded_message}} # pylint: disable=E1101 draft = ( service.users() .drafts() .create(userId="me", body=create_draft_request_body) .execute() ) print(f'Draft id: {draft["id"]}\nDraft message: {draft["message"]}') except HttpError as error: print(f"An error occurred: {error}") draft = None return draft def build_file_part(file): """Creates a MIME part for a file. Args: file: The path to the file to be attached. Returns: A MIME part that can be attached to a message. """ content_type, encoding = mimetypes.guess_type(file) if content_type is None or encoding is not None: content_type = "application/octet-stream" main_type, sub_type = content_type.split("/", 1) if main_type == "text": with open(file, "rb"): msg = MIMEText("r", _subtype=sub_type) elif main_type == "image": with open(file, "rb"): msg = MIMEImage("r", _subtype=sub_type) elif main_type == "audio": with open(file, "rb"): msg = MIMEAudio("r", _subtype=sub_type) else: with open(file, "rb"): msg = MIMEBase(main_type, sub_type) msg.set_payload(file.read()) filename = os.path.basename(file) msg.add_header("Content-Disposition", "attachment", filename=filename) return msg if __name__ == "__main__": gmail_create_draft_with_attachment()
发送消息
创建消息后,您可以在对 messages.send
的调用的请求正文中提供该消息,从而发送该消息,如以下示例所示。
Java
import com.google.api.client.googleapis.json.GoogleJsonError; import com.google.api.client.googleapis.json.GoogleJsonResponseException; import com.google.api.client.http.HttpRequestInitializer; import com.google.api.client.http.javanet.NetHttpTransport; import com.google.api.client.json.gson.GsonFactory; import com.google.api.services.gmail.Gmail; import com.google.api.services.gmail.GmailScopes; import com.google.api.services.gmail.model.Message; import com.google.auth.http.HttpCredentialsAdapter; import com.google.auth.oauth2.GoogleCredentials; import java.io.ByteArrayOutputStream; import java.io.IOException; import java.util.Properties; import javax.mail.MessagingException; import javax.mail.Session; import javax.mail.internet.InternetAddress; import javax.mail.internet.MimeMessage; import org.apache.commons.codec.binary.Base64; /* Class to demonstrate the use of Gmail Send Message API */ public class SendMessage { /** * Send an email from the user's mailbox to its recipient. * * @param fromEmailAddress - Email address to appear in the from: header * @param toEmailAddress - Email address of the recipient * @return the sent message, {@code null} otherwise. * @throws MessagingException - if a wrongly formatted address is encountered. * @throws IOException - if service account credentials file not found. */ public static Message sendEmail(String fromEmailAddress, String toEmailAddress) throws MessagingException, IOException { /* Load pre-authorized user credentials from the environment. TODO(developer) - See https://developers.google.com/identity for guides on implementing OAuth2 for your application.*/ GoogleCredentials credentials = GoogleCredentials.getApplicationDefault() .createScoped(GmailScopes.GMAIL_SEND); HttpRequestInitializer requestInitializer = new HttpCredentialsAdapter(credentials); // Create the gmail API client Gmail service = new Gmail.Builder(new NetHttpTransport(), GsonFactory.getDefaultInstance(), requestInitializer) .setApplicationName("Gmail samples") .build(); // Create the email content String messageSubject = "Test message"; String bodyText = "lorem ipsum."; // Encode as MIME message Properties props = new Properties(); Session session = Session.getDefaultInstance(props, null); MimeMessage email = new MimeMessage(session); email.setFrom(new InternetAddress(fromEmailAddress)); email.addRecipient(javax.mail.Message.RecipientType.TO, new InternetAddress(toEmailAddress)); email.setSubject(messageSubject); email.setText(bodyText); // Encode and wrap the MIME message into a gmail message ByteArrayOutputStream buffer = new ByteArrayOutputStream(); email.writeTo(buffer); byte[] rawMessageBytes = buffer.toByteArray(); String encodedEmail = Base64.encodeBase64URLSafeString(rawMessageBytes); Message message = new Message(); message.setRaw(encodedEmail); try { // Create send message message = service.users().messages().send("me", message).execute(); System.out.println("Message id: " + message.getId()); System.out.println(message.toPrettyString()); return message; } catch (GoogleJsonResponseException e) { // TODO(developer) - handle error appropriately GoogleJsonError error = e.getDetails(); if (error.getCode() == 403) { System.err.println("Unable to send message: " + e.getDetails()); } else { throw e; } } return null; } }
Python
import base64 from email.message import EmailMessage import google.auth from googleapiclient.discovery import build from googleapiclient.errors import HttpError def gmail_send_message(): """Create and send an email message Print the returned message id Returns: Message object, including message id Load pre-authorized user credentials from the environment. TODO(developer) - See https://developers.google.com/identity for guides on implementing OAuth2 for the application. """ creds, _ = google.auth.default() try: service = build("gmail", "v1", credentials=creds) message = EmailMessage() message.set_content("This is automated draft mail") message["To"] = "[email protected]" message["From"] = "[email protected]" message["Subject"] = "Automated draft" # encoded message encoded_message = base64.urlsafe_b64encode(message.as_bytes()).decode() create_message = {"raw": encoded_message} # pylint: disable=E1101 send_message = ( service.users() .messages() .send(userId="me", body=create_message) .execute() ) print(f'Message Id: {send_message["id"]}') except HttpError as error: print(f"An error occurred: {error}") send_message = None return send_message if __name__ == "__main__": gmail_send_message()
如果您尝试发送回复,并希望电子邮件形成会话,请确保:
Subject
标头匹配References
和In-Reply-To
标头遵循 RFC 2822 标准。
如需了解如何从草稿发送消息,请参阅创建草稿。