使用 Gmail API 傳送電子郵件的方式有兩種:
- 您可以使用
messages.send
方法直接傳送該字串。 - 您可以使用
drafts.send
方法,從草稿中傳送。
電子郵件會以 Base64url 編碼字串的形式傳送,且位於訊息資源的 raw
屬性中。傳送電子郵件的高階工作流程如下:
- 以簡便的方式建立電子郵件內容,並將其編碼為 Base64url 字串。
- 建立新的訊息資源,並將
raw
屬性設為您剛建立的 Base64url 字串。 - 呼叫
messages.send
;如果傳送草稿,請呼叫drafts.send
。
此工作流程的詳細資料可能因您選擇的用戶端程式庫和程式設計語言而異。
建立訊息
Gmail API 規定 MIME 電子郵件符合 RFC 2822 規定,並採用 Base64url 字串編碼。許多程式設計語言都有程式庫或公用程式,可簡化建立和編碼 MIME 訊息的程序。以下程式碼範例示範如何使用適用於不同語言的 Google API 用戶端程式庫,建立 MIME 訊息。
Java
在 javax.mail.internet
套件中使用 MimeMessage
類別,大幅簡化電子郵件的建立過程。以下範例說明如何建立電子郵件,包括標頭:
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; } }
下一步是對 MimeMessage
進行編碼,將 Message
物件例項化,然後將採用 Base64url 編碼的訊息字串設為 raw
屬性的值。
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
下列程式碼範例示範如何建立 MIME 訊息、對 Base64url 字串進行編碼,以及如何指派給 Message
資源的 raw
欄位:
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"] = "gduser1@workspacesamples.dev" message["From"] = "gduser2@workspacesamples.dev" 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()
建立含有附件的訊息
建立含有附件的訊息與建立其他郵件類似,但將檔案上傳為多部分 MIME 訊息的程序取決於程式設計語言。以下程式碼範例示範如何建立含有附件的多部分 MIME 訊息。
Java
以下範例說明如何建立多部分 MIME 郵件,編碼和指派步驟與上述相同。
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
與上一個範例類似,這個範例也會處理訊息編碼至 base64url 的作業,並指派給 Message
資源的 raw
欄位。
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"] = "gduser1@workspacesamples.dev" mime_message["From"] = "gduser2@workspacesamples.dev" 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()
傳送訊息
建立訊息後,只要在對 messages.send
的呼叫要求主體中提供訊息,即可傳送訊息,如以下範例所示。
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"] = "gduser1@workspacesamples.dev" message["From"] = "gduser2@workspacesamples.dev" 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()
如果您想傳送回覆,並想將電子郵件加入討論串,請確認下列事項:
- 「
Subject
」標頭相符 References
和In-Reply-To
標頭符合 RFC 2822 標準。
如要進一步瞭解如何透過草稿傳送訊息,請參閱「建立草稿」一文。