springboot 邮箱发送群发并且发送多个附件

在 Spring Boot 中，实现邮箱的群发和发送多个附件可以使用 JavaMail API。下面是一个简单的示例代码：

import java.io.File;
import java.util.Properties;

import javax.mail.Authenticator;
import javax.mail.Message;
import javax.mail.MessagingException;
import javax.mail.Session;
import javax.mail.Transport;
import javax.mail.internet.InternetAddress;
import javax.mail.internet.MimeBodyPart;
import javax.mail.internet.MimeMessage;
import javax.mail.internet.MimeMultipart;
import javax.mail.internet.MimeUtility;

public class EmailService {

    private String host; // SMTP服务器主机名
    private String username; // 发件人账号
    private String password; // 发件人密码

    public EmailService(String host, String username, String password) {
        this.host = host;
        this.username = username;
        this.password = password;
    }

    public void sendEmail(String[] to, String[] cc, String[] bcc, String subject, String content, String[] attachments) throws Exception {
        Properties props = new Properties();
        props.put("mail.smtp.host", host);
        props.put("mail.smtp.auth", "true");
        props.put("mail.smtp.ssl.enable", "true");

        Authenticator auth = new EmailAuthenticator(username, password);

        Session mailSession = Session.getInstance(props, auth);

        MimeMessage message = new MimeMessage(mailSession);
        message.setFrom(new InternetAddress(username));

        InternetAddress[] toAddresses = new InternetAddress[to.length];
        for (int i = 0; i < to.length; i++) {
            toAddresses[i] = new InternetAddress(to[i]);
        }
        message.setRecipients(Message.RecipientType.TO, toAddresses);

        if (cc != null && cc.length > 0) {
            InternetAddress[] ccAddresses = new InternetAddress[cc.length];
            for (int i = 0; i < cc.length; i++) {
                ccAddresses[i] = new InternetAddress(cc[i]);
            }
            message.setRecipients(Message.RecipientType.CC, ccAddresses);
        }

        if (bcc != null && bcc.length > 0) {
            InternetAddress[] bccAddresses = new InternetAddress[bcc.length];
            for (int i = 0; i < bcc.length; i++) {
                bccAddresses[i] = new InternetAddress(bcc[i]);
            }
            message.setRecipients(Message.RecipientType.BCC, bccAddresses);
        }

        message.setSubject(subject);

        MimeMultipart contentPart = new MimeMultipart();
        MimeBodyPart textPart = new MimeBodyPart();
        textPart.setText(content);
        contentPart.addBodyPart(textPart);

        if (attachments != null && attachments.length > 0) {
            for (String attachment : attachments) {
                MimeBodyPart attachPart = new MimeBodyPart();
                File file = new File(attachment);
                attachPart.attachFile(file);
                attachPart.setFileName(MimeUtility.encodeText(file.getName()));
                contentPart.addBodyPart(attachPart);
            }
        }

        message.setContent(contentPart);

        Transport.send(message);
    }

    private static class EmailAuthenticator extends Authenticator {

        private String username;
        private String password;

        public EmailAuthenticator(String username, String password) {
            this.username = username;
            this.password = password;
        }

        @Override
        protected javax.mail.PasswordAuthentication getPasswordAuthentication() {
            return new javax.mail.PasswordAuthentication(username, password);
        }
    }
}

然后就可以在你的代码中使用这个 EmailService 类来发送邮件了：

EmailService emailService = new EmailService("smtp.example.com", "username@example.com", "password");
String[] to = {"recipient1@example.com", "recipient2@example.com"};
String[] cc = {"cc1@example.com", "cc2@example.com"};
String[] bcc = {"bcc1@example.com", "bcc2@example.com"};
String subject = "Test email";
String content = "This is a test email.";
String[] attachments = {"/path/to/attachment1", "/path/to/attachment2"};
emailService.sendEmail(to, cc, bcc, subject, content, attachments);

其中，`to`、`cc`、`bcc` 分别表示邮件的收件人、抄送人、密送人，`subject` 表示邮件主题，`content` 表示邮件内容，`attachments` 表示邮件的附件路径数组。