Feature Request : Sending attachments via Stream

[kiwisincebirth]

Current State

The current API for creating a mail message with email attachments i.e.

// usage example (except) from documentation
Message message = Message.builder().attachment(ATTACHMENT_1)

// the builder method signatures
public Message.MessageBuilder attachment(File attachment)
public Message.MessageBuilder attachment(List<File> attachments)

The API utilises The java.io.File class to indicate the resource to be included / attached to the email. From the File java doc An abstract representation of file and directory pathnames. - Which means the API will only work for attachments, that are stored as files in a file filesystem.

Issue

In a server side application data (files) is generally not stored in a file system. It can be stored in a database or in another location or service. In my scenario the attachment is downloaded from a private web service via HTTPS.

To use the API I have to download the attachment and store it in as a local file system. This creates several issues based a double handling writing to and reading from the file system, performance, latency, resource use, etc

Enhancement

Like most modern programming languages Java support the concept of a stream data from a producer to consumer. This is in the form of the InputStream and OutputStream api's.

Ideally MessageBuilder should be enhanced to support streaming of attachments, which vastly improves the flexibility for providing attachment data.

[szagr]

@kiwisincebirth, thank you for raising this topic.
Support streaming of attachments will be added in the next release.

[szagr]

In v1.0.5 was added FormData support.
Example:
https://github.com/mailgun/mailgun-java/blob/main/src/test/java/com/mailgun/integration/MailgunMessagesIntegrationTest.java#L212
Currently, only one FormData can be used.
Multiple FormData support may be implemented later
OpenFeign/feign-form#91
Or we can implement some workaround ourselves.

[szagr]

@kiwisincebirth Multiple FormData attachment support was added in v1.0.5.