Loading .eml files into javax.mail.Messages

Question

I'm trying to unit test a method which processes javax.mail.Message instances.

I am writing a converter to change emails which arrive in different formats and are then converted into a consistent internal format (MyMessage). This conversion will usually depend on the from-address or reply-address of the email, and the parts of the email, the subject, and the from- and reply-addresses will be required for creating the new MyMessage.

I have a collection of raw emails which are saved locally as .eml files, and I'd like to make a unit test which loads the .eml files from the classpath and converts them to javax.mail.Message instances. Is this possible, and if so, how would it be done?

Answer 1

After a few tests, I finally successfully loaded a message using the MimeMessage(Session, InputStream) public constructor (as opposed to the Folder-based protected one cited in the other response).

import java.io.FileInputStream;
import java.io.InputStream;

import javax.mail.internet.MimeMessage;

public class LoadEML {

    public static void main(String[] args) throws Exception {
        InputStream is = new FileInputStream(args[0]);
        MimeMessage mime = new MimeMessage(null, is);
        System.out.println("Subject: " + mime.getSubject());
    }

}