通过 javax.mail 实现一个发送邮件的工具类（支持发送匿名邮件、附件邮件） 可用于发送简单的预警日志等场景 工具类 MailSender.java： ``` package com.fiebug.common.util; import javax.activation.DataHandler; import javax.activation.DataSource; import javax.mail.Message; import javax.mail.MessagingException; import javax.mail.Session; import javax.mail.Transport; import javax.mail.internet.*; import javax.naming.Context; import javax.naming.NamingEnumeration; import javax.naming.NamingException; import javax.naming.directory.Attribute; import javax.naming.directory.Attributes; import javax.naming.directory.DirContext; import javax.naming.directory.InitialDirContext; import javax.net.ssl.SSLSocketFactory; import java.io.UnsupportedEncodingException; import java.util.Date; import java.util.Hashtable; import java.util.Properties; /** * 邮件发送者 * * @author Null / test@fiebug.com */ public class MailSender { private String host; private String port; private String user; private String password; private boolean isAnonymous = false; private boolean debug = false; private static final String CHARACTER_ENCODING = "UTF-8"; private static final String MAIL_TYPE = "text/html;charset=UTF-8"; private static final String ANONYMOUS_EMAIL = "anonymous@anonymous.com"; private MailSender() { this.isAnonymous = true; } private MailSender(String host, String port, String user, String password) { this.host = host; this.port = port; this.user = user; this.password = password; } /** * 获取匿名 MailSender 实例 * * @return */ public static MailSender getInstance() { return new MailSender(); } /** * 获取 MailSender 实例 * * @param host * @param port * @param user * @param password * @return */ public static MailSender getInstance(String host, String port, String user, String password) { return new MailSender(host, port, user, password); } /** * 发送邮件 * * @param from 发送者邮箱 * @param to 接收者邮箱 * @param subject 主题 * @param content 正文 * @param attachments DataSource 接口常用的实现有 FileDataSource ByteArrayDataSource * @return */ public void sendMessage(String from, String to, String subject, String content, DataSource... attachments) { try { if (from == null || from.isEmpty()) { from = ANONYMOUS_EMAIL; } MimeMultipart mimeMultipart = new MimeMultipart(); // 添加正文 MimeBodyPart contentMimeBody = new MimeBodyPart(); contentMimeBody.setContent(content, MAIL_TYPE); mimeMultipart.addBodyPart(contentMimeBody); // 添加附件 MimeBodyPart bodyPart; String nameEncoded; for (DataSource attachment : attachments) { bodyPart = new MimeBodyPart(); bodyPart.setDataHandler(new DataHandler(attachment)); nameEncoded = encodeText(attachment.getName()); // 普通附件文件名 bodyPart.setFileName(nameEncoded); String contentType = attachment.getContentType(); if (contentType != null && contentType.toLowerCase().startsWith("image/")) { // 图片附件，用于正文中引用图片 bodyPart.setContentID(nameEncoded); } mimeMultipart.addBodyPart(bodyPart); } sendMessage(from, to, subject, mimeMultipart); } catch (Exception e) { throw new RuntimeException(e); } } /** * 发送邮件 * * @param from 发送者邮箱 * @param to 接收者邮箱 * @param subject 主题 * @param mimeMultipart 主体部分 * @throws MessagingException * @throws UnsupportedEncodingException */ private void sendMessage(String from, String to, String subject, MimeMultipart mimeMultipart) throws MessagingException, UnsupportedEncodingException { if (isAnonymous) { host = getMxHost(to, null); port = "25"; } // 获取 Session String sslSocketFactory = SSLSocketFactory.class.getName(); Properties properties = new Properties(); properties.setProperty("mail.transport.protocol", "smtp"); properties.setProperty("mail.smtp.host", host); properties.setProperty("mail.smtp.port", port); properties.setProperty("mail.smtp.auth", String.valueOf(!isAnonymous)); properties.setProperty("mail.smtp.socketFactory.class", sslSocketFactory); Session session = Session.getInstance(properties); session.setDebug(debug); // 建立连接并发送邮件 Transport transport = session.getTransport(); if (isAnonymous) { transport.connect(); } else { transport.connect(user, password); } MimeMessage mimeMessage = new MimeMessage(session); mimeMessage.setFrom(new InternetAddress(from)); mimeMessage.setRecipients(Message.RecipientType.TO, to); mimeMessage.setSubject(MimeUtility.encodeText(subject, CHARACTER_ENCODING, null)); mimeMessage.setContent(mimeMultipart); mimeMessage.setHeader("X-Mailer", "JavaMail"); mimeMessage.setSentDate(new Date()); transport.sendMessage(mimeMessage, mimeMessage.getAllRecipients()); transport.close(); } /** * 根据邮箱获取对应的 MX 记录值 * * @param email * @param dns * @return */ private String getMxHost(String email, String dns) { final String regexp = "^(\\d+) (.+)\\.$"; try { // 设置 DNS 服务器 if (dns == null) { dns = "dns://"; } else { dns = "dns://" + dns; } // 获取邮件地址中的域名 String[] emailArr = email.split("@"); if (emailArr.length != 2) { throw new RuntimeException("email address error."); } String domain = emailArr[1]; // 通过 DNS 获取域名 MX 记录 Hashtable env = new Hashtable<>(); env.put(Context.INITIAL_CONTEXT_FACTORY, "com.sun.jndi.dns.DnsContextFactory"); env.put(Context.PROVIDER_URL, dns); DirContext dirContext = new InitialDirContext(env); Attributes attributes = dirContext.getAttributes(domain, new String[]{"MX"}); // 取出一组 MX 记录中第一个 Attribute mxAttribute = attributes.get("MX"); if (mxAttribute == null || mxAttribute.size() <= 0) { return null; } NamingEnumeration attributeAll = mxAttribute.getAll(); int mxPriority = Integer.MAX_VALUE; String mxValue = null; while (attributeAll.hasMore()) { String mxs = (String) attributeAll.next(); int priority = Integer.parseInt(mxs.replaceAll(regexp, "$1")); String value = mxs.replaceAll(regexp, "$2"); // 取优先级最高的值 if (priority < mxPriority) { mxPriority = priority; mxValue = value; } } return mxValue; } catch (NamingException e) { return null; } } private String encodeText(String text) { try { return MimeUtility.encodeText(text, CHARACTER_ENCODING, null); } catch (UnsupportedEncodingException e) { // ignore } return text; } public boolean isDebug() { return debug; } public void setDebug(boolean debug) { this.debug = debug; } } ``` 依赖的包： ``` javax.mail mail 1.4.7 ```