使用javamail将字符串作为附件发送会得到重复的内容

Question

I'm struggling to send a csv file over javamail.

Since the content is small, I constructed manually the data as CSV format, stored in memory and passed as ByteArrayDataSource to MimeMessageHelper . However, the received file has strangely double the content.

The code is pretty standard:

// mail sender
try {
            MimeMessage mail = javaMailSender.createMimeMessage();
            MimeMessageHelper helper = new MimeMessageHelper(mail, true, "UTF-8");
            helper.setSubject(mailObj.getMailSubject());
            helper.setFrom(mailObj.getMailFrom());
            helper.setTo(mailObj.getMailTo());
            Mail.Attachment attachment = mailObj.getAttachment();
            if (attachment != null) helper.addAttachment(attachment.getFilename(),
                                                         attachment.getDataSource());
            javaMailSender.send(helper.getMimeMessage());
        } catch (Exception e) {
            log.error("Cannot send email " + mailObj.toString(), e);
        }

DataSource createDataSource(Data originalData) throws IOException {
        try (StringWriter out = new StringWriter(); PrintWriter pw = new PrintWriter(out) {
            @Override
            public void println() {
                write(LINE_SEP);
            }
        }) {
            pw.write('\uFEFF'); // Write BOM
            pw.println(HEADERS);
            for (AppointmentBookingEvent details : appointments) {
                // Concatenate the data with PrintWriter.println(...);
            }
            return new ByteArrayDataSource(out.toString().getBytes(StandardCharsets.UTF_8), "text/csv");
        }
    }

I noticed that the method DataSource.getInputStream() is called twice by the sender's internal functions. Was that by any chance the cause ?

Answer 1

I'm struggling to send a csv file over javamail.

Since the content is small, I constructed manually the data as CSV format, stored in memory and passed as ByteArrayDataSource to MimeMessageHelper . However, the received file has strangely double the content.

The code is pretty standard:

// mail sender
try {
            MimeMessage mail = javaMailSender.createMimeMessage();
            MimeMessageHelper helper = new MimeMessageHelper(mail, true, "UTF-8");
            helper.setSubject(mailObj.getMailSubject());
            helper.setFrom(mailObj.getMailFrom());
            helper.setTo(mailObj.getMailTo());
            Mail.Attachment attachment = mailObj.getAttachment();
            if (attachment != null) helper.addAttachment(attachment.getFilename(),
                                                         attachment.getDataSource());
            javaMailSender.send(helper.getMimeMessage());
        } catch (Exception e) {
            log.error("Cannot send email " + mailObj.toString(), e);
        }

DataSource createDataSource(Data originalData) throws IOException {
        try (StringWriter out = new StringWriter(); PrintWriter pw = new PrintWriter(out) {
            @Override
            public void println() {
                write(LINE_SEP);
            }
        }) {
            pw.write('\uFEFF'); // Write BOM
            pw.println(HEADERS);
            for (AppointmentBookingEvent details : appointments) {
                // Concatenate the data with PrintWriter.println(...);
            }
            return new ByteArrayDataSource(out.toString().getBytes(StandardCharsets.UTF_8), "text/csv");
        }
    }

I noticed that the method DataSource.getInputStream() is called twice by the sender's internal functions. Was that by any chance the cause ?