How to get the whole attachment as a MimeMessage?

Question

I'm finding a way to deal with base64 encoded .eml attachment. I need to parse it to MimeMessage for further process
   for (i=0; i<part.getCount(); i++) {
        currentPart = (MimePart) part.getBodyPart(i);
        if ( file extension is .eml ) {
            InputStream input = currentPart.getInputStream();
            currentPart = new MimeMessage(null, input);
        }with the above code, I would only get the decoded body of the email content, all header information are missing.
From JavaMail API, getInputStream() and writeTo() would only get/write the content part, so I've tried to use:
   for(Enumeration enum = currentPart.getAllHeaderLines(); enum.hasMoreElements();)     {
        currentPart.addHeaderLine((String)enum.nextElement());
   }          I suppose currentPart is a MimeMessage now, but when I try this:
   request.setAttribute("part", (MimeMessage) currentPart.getContent());I would get a ClassCastException
Would anyone give me some suggestion?

Answer 1

I am a little unsure as to what exactly you are trying to achieve, but I will assume you are trying to extract the attachment from one message and parse this attachment as a MimeMessage.
First, the parts in a MimeMessage are grouped in a tree structure so you can't just iterate over the list of parts and expect to get them all, you have to do it recursively.
eg., (pseudo code only)
public void getParts(Part p, List parts) {
  if(p.getContent() != null) {
    if(p.getContent() instanceof Multipart) {
      Multipart mp = (Multipart) content;
      for(int i = 0; i < mp.getCount(); i++) {
        getParts(mp.getBodyPart(i), parts);
    else
       parts.add(p);
// Then call it like:
List parts = new LinkedList();
getParts(part, parts);
// Where "part" is your original messageOnce you have the list of parts, you need to find the attachment. This is done by looking at the "disposition" of the part.
An attachment will usually (although not always) be of type MimeMessage.INLINE or MimeMessage.ATTACHMENT
So... iterate though your parts list looking for attachments
Iterator i = parts.iterator();
Part p = null;
MimeMessage attachment = null;
while(i.hasNext()) {
  p = (Part)i.next();
  // NOTE: p.getDisposition() may be null here
  if(p.getDisposition().equals(MimeMessage.INLINE) || p.getDisposition().equals(MimeMessage.ATTACHMENT)) {
    // You have an attachment
    // Use the data handler to get the stream
    InputStream input= p.getDataHandler().getInputStream();
    // Construct you new MimeMessage
    attachment = new MimeMessage(null, input);
    // Exit the loop
    break;
}The simplest way to test is you have your attachment is to print it's filename with p.getFileName();
You can also bypass creating the part list by adding the disposition check to the first getParts method.