实际开发中电子邮件的应用非常广泛，比如注册激活邮件，邮件找回密码，自动批量发送活动信息等。本文介绍如何通过 Java 代码来创建支持附件、支持多收件人、多抄送人、多密送人的复杂电子邮件，并连接邮件服务器发送邮件。
电子邮件协议
常用的电子邮件协议包括 SMTP，POP3，IMAP，其中邮件的创建和发送只需要用到 SMTP协议，所以代码也只涉SMTP协议，SMTP 是 Simple Mail Transfer Protocol 的简称，即简单邮件传输协议。
JavaMail
Java 官方也提供了对电子邮件协议封装的 Java 类库JavaMail，自行官网下载。
mvn项目的话，添加依赖如下：
<!-- JavaMail邮件发送 --><dependency><groupId>javax.mail</groupId><artifactId>mail</artifactId><version>1.5.0-b01</version></dependency>
创建一封电子邮件的步骤:
1. 创建一个邮件对象（MimeMessage）并链接到邮件服务器；
2. 设置发件人、收件人(可多个收件人、抄送人、密送人)、邮件的主题（标题）、正文（内容）、显示的发送时间；
3. 发送。
准备工作：
发送邮件首先需要有一个邮箱账号和密码，本文以qq邮箱为例，邮箱账号必须要开启 SMTP 服务，在浏览器网页登录邮箱后一般在邮箱的“设置”选项中可以开启，并记下授权码，如下所示（其他邮箱大同小异）:
实现代码如下：
实体类EmailBean.java：
package mon.bean.email;import mon.bean.email.EmailUser;import java.util.List;/*** @author weny.yang* @ClassName: EmailBean* @Description:邮件实体* @date Nov 2, */public class EmailBean {private String smtpHost;// 发件人邮箱的 SMTP 服务器地址private EmailUser fromUser;// 发件人private List<EmailUser> recipientType_TO;//(必填) 收件人，可以配置多个private List<EmailUser> recipientType_CC;//(可选) 抄送人，可以配置多个private List<EmailUser> recipientType_BCC;//(可选) 密送人，可以配置多个,其他人无法知道密送人收到邮件private String emailTitle;// 邮件主题private String emailContent;// 邮件内容private List<String> annexPaths;// 附件路径public EmailBean() {super();}public EmailBean(String smtpHost, EmailUser fromUser, List<EmailUser> recipientType_TO, List<EmailUser> recipientType_CC,List<EmailUser> recipientType_BCC, String emailTitle, String emailContent, List<String> annexPaths) {super();this.smtpHost = smtpHost;this.fromUser = fromUser;this.recipientType_TO = recipientType_TO;this.recipientType_CC = recipientType_CC;this.recipientType_BCC = recipientType_BCC;this.emailTitle = emailTitle;this.emailContent = emailContent;this.annexPaths = annexPaths;}public String getSmtpHost() {return smtpHost;}public void setSmtpHost(String smtpHost) {this.smtpHost = smtpHost;}public EmailUser getFromUser() {return fromUser;}public void setFromUser(EmailUser fromUser) {this.fromUser = fromUser;}public List<EmailUser> getRecipientType_TO() {return recipientType_TO;}public void setRecipientType_TO(List<EmailUser> recipientType_TO) {this.recipientType_TO = recipientType_TO;}public List<EmailUser> getRecipientType_CC() {return recipientType_CC;}public void setRecipientType_CC(List<EmailUser> recipientType_CC) {this.recipientType_CC = recipientType_CC;}public List<EmailUser> getRecipientType_BCC() {return recipientType_BCC;}public void setRecipientType_BCC(List<EmailUser> recipientType_BCC) {this.recipientType_BCC = recipientType_BCC;}public String getEmailTitle() {return emailTitle;}public void setEmailTitle(String emailTitle) {this.emailTitle = emailTitle;}public String getEmailContent() {return emailContent;}public void setEmailContent(String emailContent) {this.emailContent = emailContent;}public List<String> getAnnexPaths() {return annexPaths;}public void setAnnexPaths(List<String> annexPaths) {this.annexPaths = annexPaths;}public String toString() {return "{smtpHost=" + smtpHost + ",fromUser=" + fromUser + ",recipientType_TO=" + recipientType_TO+ ",recipientType_CC=" + recipientType_CC + ",recipientType_BCC=" + recipientType_BCC + ",emailTitle="+ emailTitle + ",emailContent=" + emailContent + ",annexPaths = " + annexPaths + "}";}}
实体类EmailUser.java：
package mon.bean.email;/*** @author weny.yang* @ClassName: User* @Description:发件人/收件人/抄送人/密送人* @date 11月10日*/public class EmailUser {private String name;// 昵称private String address;// 邮箱地址private String authCode;// 授权码(发件人需要，收件人/抄送人/密送人不需要)/*** 构造函数 User.发件人*/public EmailUser(String name, String address, String authCode) {super();this.name = name;this.address = address;this.authCode = authCode;}/*** 构造函数 User.收件人/抄送人/密送人*/public EmailUser(String address) {super();this.address = address;}public String getName() {return name;}public void setName(String name) {this.name = name;}public String getAddress() {return address;}public void setAddress(String address) {this.address = address;}public String getAuthCode() {return authCode;}public void setAuthCode(String authCode) {this.authCode = authCode;}public String toString() {return "{name=" + name + ",address=" + address + "}";}}
工具类：
package mon.utils.email;import java.io.File;import java.util.Date;import java.util.List;import java.util.Properties;import javax.activation.DataHandler;import javax.activation.FileDataSource;import javax.mail.*;import javax.mail.internet.InternetAddress;import javax.mail.internet.MimeBodyPart;import javax.mail.internet.MimeMessage;import javax.mail.internet.MimeMultipart;import mon.bean.email.EmailBean;import mon.bean.email.EmailUser;import lombok.extern.slf4j.Slf4j;import com.sun.mail.util.MailSSLSocketFactory;/*** @author weny.yang* @ClassName: EmailUtil* @Description:复杂邮件发送工具，支持附件* @date 11月9日*/@Slf4jpublic class EmailUtil {/*** @Title: sendEmail* @Description:发送复杂邮件* @author weny.yang*/public static void sendEmail(EmailBean bean) {Transport transport = null;try {log.info("发送邮件开始[" + bean.getEmailTitle() + "]");Properties prop = new Properties();prop.setProperty("mail.host", bean.getSmtpHost()); // 邮件服务器prop.setProperty("mail.transport.protocol", "smtp"); // 邮件发送协议prop.setProperty("mail.smtp.auth", "true"); // 需要验证用户名密码// SSL加密MailSSLSocketFactory sf = new MailSSLSocketFactory();sf.setTrustAllHosts(true);prop.put("mail.smtp.ssl.enable", "true");prop.put("mail.smtp.ssl.socketFactory", sf);// 1、创建应用程序所需的环境会话 session 对象Session session = Session.getDefaultInstance(prop, new Authenticator() {@Overrideprotected PasswordAuthentication getPasswordAuthentication() {// 发件人的邮箱地址和授权码return new PasswordAuthentication(bean.getFromUser().getAddress(), bean.getFromUser().getAuthCode());}});// 2、获取 transport 对象transport = session.getTransport();// 3、连接邮箱服务器transport.connect(bean.getSmtpHost(), bean.getFromUser().getAddress(), bean.getFromUser().getAuthCode());// 4、创建复杂邮件MimeMessage mimeMessage = creatComplexEmail(session, bean);// 5、发送邮件transport.sendMessage(mimeMessage, mimeMessage.getAllRecipients());log.info("发送邮件完成[" + bean.getEmailTitle() + "]");} catch (Exception e) {log.error("邮件发送异常", e);} finally {try {if (null != transport) {// 6、关闭连接transport.close();}} catch (MessagingException e) {log.error("资源释放异常", e);}}}/*** @Title: complexEmail* @Description:创建复杂邮件* @author weny.yang*/private static MimeMessage creatComplexEmail(Session session, EmailBean bean) throws Exception {// 消息信息MimeMessage message = new MimeMessage(session);// 发件人message.setFrom(new InternetAddress(bean.getFromUser().getAddress(), bean.getFromUser().getName(), "UTF-8"));// 收件人List<EmailUser> toList = bean.getRecipientType_TO();if (toList != null && toList.size() > 0) {for (EmailUser user : toList) {message.setRecipient(MimeMessage.RecipientType.TO, new InternetAddress(user.getAddress(), user.getName(), "UTF-8"));}}// 抄送人List<EmailUser> ccList = bean.getRecipientType_CC();if (ccList != null && ccList.size() > 0) {for (EmailUser user : ccList) {message.setRecipient(, new InternetAddress(user.getAddress(), user.getName(), "UTF-8"));}}// 密送人List<EmailUser> bccList = bean.getRecipientType_BCC();if (bccList != null && bccList.size() > 0) {for (EmailUser user : bccList) {message.setRecipient(MimeMessage.RecipientType.BCC, new InternetAddress(user.getAddress(), user.getName(), "UTF-8"));}}// 邮件标题message.setSubject(bean.getEmailTitle());// 邮件文本MimeBodyPart text = new MimeBodyPart();text.setContent(bean.getEmailContent(), "text/html;charset=utf-8");// 支持html标签解析，展示自定义格式// 组装邮件MimeMultipart allFile = new MimeMultipart();// 添加文本allFile.addBodyPart(text);// 添加附件List<String> annexPaths = bean.getAnnexPaths();if (annexPaths != null && annexPaths.size() > 0) {for (String path : annexPaths) {MimeBodyPart appendix = new MimeBodyPart();DataHandler dataHandler = new DataHandler(new FileDataSource(path));appendix.setDataHandler(dataHandler);appendix.setFileName(new File(path).getName());allFile.addBodyPart(appendix);//设置附件}}allFile.setSubType("mixed"); //正文和附件都存在邮件中，所有类型设置为mixed// 放到Message消息中message.setContent(allFile);// 显示的发件时间message.setSentDate(new Date());message.saveChanges();//保存修改return message;}}
运行效果：
