Mail 源码分析

模块文件结构

.
├── __init__.py
├── backends
│   ├── __init__.py
│   ├── base.py
│   ├── console.py
│   ├── dummy.py
│   ├── filebased.py
│   ├── locmem.py
│   └── smtp.py
├── message.py
└── utils.py

模块结构

• backends: 邮件后端，包括 console,dummy,filebased,localmem,smtp
• message: 主要是消息的抽象，分为 plaintext,html 两类

ConsoleEmailBackend 类

属性

1. stream: 输出流

方法

1. send_messages(email_messages): 发送邮件

def write_message(self, message):msg = message.message()msg_data = msg.as_bytes()charset = (msg.get_charset().get_output_charset() if msg.get_charset() else "utf-8")msg_data = msg_data.decode(charset)self.stream.write("%s\n" % msg_data)self.stream.write("-" * 79)self.stream.write("\n")def send_messages(self, email_messages):"""Write all messages to the stream in a thread-safe way."""if not email_messages:returnmsg_count = 0with self._lock:try:stream_created = self.open()for message in email_messages:self.write_message(message)self.stream.flush()  # flush after each messagemsg_count += 1if stream_created:self.close()except Exception:if not self.fail_silently:raisereturn msg_count

DummyEmailBackend 类

可以用于本地测试，验证方法调用是否成功

方法

1. send_messages(email_messages): 发送邮件

def send_messages(self, email_messages):return len(list(email_messages))

FileBasedEmailBackend 类

文件流，将邮件消息写入文件流中

方法

1. send_messages(email_messages): 发送邮件

def write_message(self, message):self.stream.write(message.message().as_bytes() + b"\n")self.stream.write(b"-" * 79)self.stream.write(b"\n")

LocmemEmailBackend 类

内存中存储邮件消息，可以用于测试或开发

方法

1. send_messages(email_messages): 发送邮件

def send_messages(self, messages):"""Redirect messages to the dummy outbox"""msg_count = 0for message in messages:  # .message() triggers header validationmessage.message()mail.outbox.append(copy.deepcopy(message))msg_count += 1return msg_count

SMTPEmailBackend 类

SMTP 邮件后端，通过 SMTP 协议发送邮件

方法

1. send_messages(email_messages): 发送邮件

def send_messages(self, email_messages):"""Send one or more EmailMessage objects and return the number of emailmessages sent."""if not email_messages:return 0with self._lock:new_conn_created = self.open()if not self.connection or new_conn_created is None:# We failed silently on open().# Trying to send would be pointless.return 0num_sent = 0try:for message in email_messages:sent = self._send(message)if sent:num_sent += 1finally:if new_conn_created:self.close()return num_sent

EmailMessage 类

属性

1. subject：邮件主题
2. body：邮件正文
3. from_email：发件人地址
4. to：收件人地址列表
5. cc：抄送人地址列表
6. bcc: 密送人地址列表
7. reply_to：回复地址列表
8. headers：自定义邮件头
9. attachments：附件列表
10. connection: 邮件服务器

方法

1. attach(): 添加附件

邮件附件如果已经是 mime.MIMEBase 的话，直接加入到附件列表中。
如果不是，先猜测 mimetype 类型，然后以(filename, content, mimetype)加入到附件列表中。

filename=None, mimetype=None 的情况，会出错。

def attach(self, filename=None, content=None, mimetype=None):"""Attach a file with the given filename and content. The filename canbe omitted and the mimetype is guessed, if not provided.If the first parameter is a MIMEBase subclass, insert it directlyinto the resulting message attachments.For a text/* mimetype (guessed or specified), when a bytes object isspecified as content, decode it as UTF-8. If that fails, set themimetype to DEFAULT_ATTACHMENT_MIME_TYPE and don't decode the content."""if isinstance(filename, MIMEBase):if content is not None or mimetype is not None:raise ValueError("content and mimetype must not be given when a MIMEBase ""instance is provided.")self.attachments.append(filename)elif content is None:raise ValueError("content must be provided.")else:mimetype = (mimetypeor mimetypes.guess_type(filename)[0]or DEFAULT_ATTACHMENT_MIME_TYPE)basetype, subtype = mimetype.split("/", 1)if basetype == "text":if isinstance(content, bytes):try:content = content.decode()except UnicodeDecodeError:# If mimetype suggests the file is text but it's# actually binary, read() raises a UnicodeDecodeError.mimetype = DEFAULT_ATTACHMENT_MIME_TYPEself.attachments.append((filename, content, mimetype))

2. message(): 生成 MIMEText 对象

def message(self):encoding = self.encoding or settings.DEFAULT_CHARSETmsg = SafeMIMEText(self.body, self.content_subtype, encoding)msg = self._create_message(msg)msg["Subject"] = self.subjectmsg["From"] = self.extra_headers.get("From", self.from_email)self._set_list_header_if_not_empty(msg, "To", self.to)self._set_list_header_if_not_empty(msg, "Cc", self.cc)self._set_list_header_if_not_empty(msg, "Reply-To", self.reply_to)# Email header names are case-insensitive (RFC 2045), so we have to# accommodate that when doing comparisons.header_names = [key.lower() for key in self.extra_headers]if "date" not in header_names:# formatdate() uses stdlib methods to format the date, which use# the stdlib/OS concept of a timezone, however, Django sets the# TZ environment variable based on the TIME_ZONE setting which# will get picked up by formatdate().msg["Date"] = formatdate(localtime=settings.EMAIL_USE_LOCALTIME)if "message-id" not in header_names:# Use cached DNS_NAME for performancemsg["Message-ID"] = make_msgid(domain=DNS_NAME)for name, value in self.extra_headers.items():if name.lower() != "from":  # From is already handledmsg[name] = valuereturn msg

EmailMultiAlternatives 类

EmailMultiAlternatives 类继承自 EmailMessage 类，增加了对 HTML 格式的支持。

总结

Django 的邮件模块提供了多种邮件后端，可以根据需要选择不同的后端。留有 dummy,console,locmem,filebased,smtp 多种类型后端。
通过 Django 邮件模块，避免重复编码，针对各类邮件服务器的特定规则只需自己实现发送后端逻辑，不需要重头编写。