java.io.IOException：使用 SpringBoot 寫入 Multipart 時出現異常

Question

賞金將在 7 天后到期。 此問題的答案有資格獲得+200聲望賞金。 Nunyet de Can Calçada正在從有信譽的來源尋找答案。

我想發送一個帶有附件的 email：

  public void sendMailWithAttachment(String to, String subject, String body, String fileToAttach) {

        MimeMessagePreparator preparator = mimeMessage -> {

            mimeMessage.setRecipient(Message.RecipientType.TO, new InternetAddress(to));
            mimeMessage.setFrom(new InternetAddress("admin@gmail.com"));
            mimeMessage.setSubject(subject);
            mimeMessage.setText(body);

            FileSystemResource file = new FileSystemResource(new File(fileToAttach));
            System.out.println(file.contentLength());
            MimeMessageHelper helper = new MimeMessageHelper(mimeMessage, true);
            helper.addAttachment("logo.jpg", file);
        };

        try {
            javaMailSender.send(preparator);
        }
        catch (MailException ex) {
            // simply log it and go on...
            System.err.println(ex.getMessage());
        }
    }

但我有這個例外：

Failed messages: javax.mail.MessagingException: IOException while sending message;
  nested exception is:
    java.io.IOException: Exception writing Multipart

Answer 1

Spring 文檔中給出的示例與您的代碼不匹配：它創建一個MimeMessageHelper object 並使用它來定義正文和附加文件。

你應該這樣做：

public void sendMailWithAttachment(String to, String subject, String body, String fileToAttach) {

        MimeMessagePreparator preparator = mimeMessage -> {

            MimeMessageHelper message = new MimeMessageHelper(mimeMessage, true, "UTF-8");
            message.setRecipient(Message.RecipientType.TO, new InternetAddress(to));
            message.setFrom(new InternetAddress("admin@gmail.com"));
            message.setSubject(subject);
            message.setText(body);

            FileSystemResource file = new FileSystemResource(new File(fileToAttach));
            message.addAttachment("logo.jpg", file);
        };

        try {
            javaMailSender.send(preparator);
        }
        catch (MailException ex) {
            // simply log it and go on...
            System.err.println(ex.getMessage());
        }
    }

Answer 2

我會以不同的方式創建MimeMessagePreparator並使用Streams來讀取文件。

public void sendMailWithAttachment(String to, String subject, String body, String fileToAttach) {

        MimeMessagePreparator preparator = mimeMessage -> {

            FileInputStream inputStream = new FileInputStream(new File(fileToAttach));

            MimeMessageHelper message = new MimeMessageHelper(mimeMessage, true, "UTF-8");
            message.setRecipient(Message.RecipientType.TO, new InternetAddress(to));
            message.setFrom(new InternetAddress("admin@gmail.com"));
            message.setSubject(subject);
            message.setText(body);            
            message.addAttachment("logo.jpg", new ByteArrayResource(IOUtils.toByteArray(inputStream)));
  
        };

        try {
            javaMailSender.send(preparator);
        }
        catch (MailException ex) {
            // simply log it and go on...
            System.err.println(ex.getMessage());
        }
    }