javax.activation.UnsupportedDataTypeException: no object DCH for MIME type multipart/mixed; boundary

Question

Currently I\'m inline of writing a code that will be listening to a directory. when the directory is updated with .apk file, I\'ll send a mail with this .apk file to a gmail

Answer 1

The answer from Som worked for me. However I had to modify the mappings as I was using JavaMail DSN, and needed those mailcap entries also (included below, including Som's answer):

// Original answer from Som:
MailcapCommandMap mc = (MailcapCommandMap) CommandMap.getDefaultCommandMap();
mc.addMailcap("text/html;; x-java-content-handler=com.sun.mail.handlers.text_html");
mc.addMailcap("text/xml;; x-java-content-handler=com.sun.mail.handlers.text_xml");
mc.addMailcap("text/plain;; x-java-content-handler=com.sun.mail.handlers.text_plain");
mc.addMailcap("multipart/*;; x-java-content-handler=com.sun.mail.handlers.multipart_mixed");
mc.addMailcap("message/rfc822;; x-java-content-handler=com.sun.mail.handlers.message_rfc822");

// Additional elements to make DSN work 
mc.addMailcap("multipart/report;;  x-java-content-handler=com.sun.mail.dsn.multipart_report");
mc.addMailcap("message/delivery-status;; x-java-content-handler=com.sun.mail.dsn.message_deliverystatus");
mc.addMailcap("message/disposition-notification;; x-java-content-handler=com.sun.mail.dsn.message_dispositionnotification");
mc.addMailcap("text/rfc822-headers;;   x-java-content-handler=com.sun.mail.dsn.text_rfc822headers");

As it turns out, it was adding the DSN JAR into my fat JAR (using shadowJar/Gradle) that caused the problem: the META-INF/mailcap from the DSN jar was overwriting the core one.