Why attachments are missing using Spring Mail? (Kotlin)

Question

I want to send an email using Spring Boot and its mail library. Here is how I implemented it: The byteArray is not null and not empty.

class Attachment(val fileName: String, val byteArray: ByteArray)
private val emailSender: JavaMailSender

[...]

private fun sendMessage(to: String, subject: String, text: String, attachments: List<Attachment>? = null) {
        val message = emailSender.createMimeMessage()
        val helper = MimeMessageHelper(message, true)
        message.setContent(text, "text/html; charset=utf-8")

        helper.setFrom(sender)
        helper.setTo(to)
        helper.setSubject(subject)

        // add attachment
        attachments?.forEach { attachment ->
            helper.addAttachment(attachment.fileName, ByteArrayResource(attachment.byteArray))
        }

        try {
            emailSender.send(message)
        } catch (e: MailException) {
            logger.warn("Email could not be sent: $to, reason: ${e.message}")
        }
}

Answer 1

If you use the mail helper class from Spring, then you also need to specify the html content there.

private fun sendMessage(to: String, subject: String, text: String, attachments: List<Attachment>? = null) {
        val message = emailSender.createMimeMessage()
        val helper = MimeMessageHelper(message, true)

        helper.setFrom(sender)
        helper.setTo(to)
        helper.setSubject(subject)
        helper.setText(text, true)

        // add attachment
        attachments?.forEach { attachment ->
            helper.addAttachment(attachment.fileName, ByteArrayResource(attachment.byteArray))
        }

        try {
            emailSender.send(message)
        } catch (e: MailException) {
            logger.warn("Email could not be sent: $to, reason: ${e.message}")
        }
}