通过 Gmail API 发送带有纯文本回退的 HTML 电子邮件
一个已回答的问题 在 StackOverflow 建议添加 html- 电子邮件正文的标记将起到作用.该解决方案正确吗?
An answered question at StackOverflow suggests that adding html-markup to the body of the email will do the trick. Is that solution correct?
但是如果收件人的电子邮件服务器/客户端不支持 HTML 电子邮件怎么办?
But what if the recipient's email server/client does not support HTML email?
例如使用 Apache 公共电子邮件 时，我执行以下操作:
E.g. when using Apache commons email, I do the following:
// set the html message
email.setHtmlMsg("<html>Our logo - <img src="cid:"+cid+""></html>");
// set the alternative message
email.setTextMsg("Your email client does not support HTML messages");
如果收件人电子邮件服务器/客户端不支持 HTML，有没有办法告诉 Gmail API 回退到哪个电子邮件?
Is there any way to tell Gmail API what email to fall back to if the recipient email server/client does not support HTML?
附:我对 Java 代码示例特别感兴趣.
P.S. I'm especially interested in Java code samples.
谢谢
推荐答案
要提供两种选择，您可以将 Content-Type 设置为 mixed/alternative 而不是其中任何一种text/plain 或 text/html:
To give two alternatives, you can set the Content-Type to mixed/alternative instead of either text/plain or text/html:
如果我们想在 API explorer，我们只是对邮件进行 Base64 编码，并将所有 / 替换为 _ 并将所有 + 替换为 <代码>-.
If we want to try this out in the API explorer, we just Base64-encode the mail, and make it url-safe by replacing all / with _ and all + with -.
在开发者控制台中:
btoa(
"Subject: Example Subject
" +
"From: <example@gmail.com>
" +
"To: <example@gmail.com>
" +
"Content-Type: multipart/alternative; boundary="foo_bar"
" +
"--foo_bar
" +
"Content-Type: text/plain; charset=UTF-8
" +
"*Bold example message text*
" +
"--foo_bar
" +
"Content-Type: text/html; charset=UTF-8
" +
"<div dir="ltr"><b>Bold example message text</b></div>
" +
"--foo_bar--"
).replace(/+/g, '-').replace(///g, '_');
POST https://www.googleapis.com/gmail/v1/users/me/messages/send?access_token={YOUR_API_KEY}
{
"raw": "U3ViamVjdDogRXhhbXBsZSBTdWJqZWN0DQpGcm9tOiA8ZXhhbXBsZUBnbWFpbC5jb20-DQpUbzogPGV4YW1wbGVAZ21haWwuY29tPg0KQ29udGVudC1UeXBlOiBtdWx0aXBhcnQvYWx0ZXJuYXRpdmU7IGJvdW5kYXJ5PSJmb29fYmFyIg0KDQotLWZvb19iYXINCkNvbnRlbnQtVHlwZTogdGV4dC9wbGFpbjsgY2hhcnNldD1VVEYtOA0KDQoqQm9sZCBleGFtcGxlIG1lc3NhZ2UgdGV4dCoNCg0KLS1mb29fYmFyDQpDb250ZW50LVR5cGU6IHRleHQvaHRtbDsgY2hhcnNldD1VVEYtOA0KDQo8ZGl2IGRpcj0ibHRyIj48Yj5Cb2xkIGV4YW1wbGUgbWVzc2FnZSB0ZXh0PC9iPjwvZGl2Pg0KDQotLWZvb19iYXItLQ=="
}
要在 Java 中做同样的事情，你可以这样做:
To do the equivalent in Java, you could do:
Message message = new MimeMessage(session);
Multipart multiPart = new MimeMultipart("alternative");
MimeBodyPart textPart = new MimeBodyPart();
textPart.setText(text, "utf-8");
MimeBodyPart htmlPart = new MimeBodyPart();
htmlPart.setContent(html, "text/html; charset=utf-8");
multiPart.addBodyPart(textPart);
multiPart.addBodyPart(htmlPart);
message.setContent(multiPart);
ByteArrayOutputStream output = new ByteArrayOutputStream();
message.writeTo(output);
String rawEmail = Base64.encodeBase64URLSafeString(output.toByteArray());
Message message = new Message();
message.setRaw(rawEmail);
message = service.users().messages().send(userId, message).execute();
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