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Some years ago I wrote a blog about emails with body and attachment with help of the MailPackage structure:

XI Mail Adapter: An approach for sending emails with attachment with help of Java mapping

 

In this blog, I will present another solution which does not use MailPackage and I show also how to add binary payloads to an email.

 

Meanwhile, there are many blogs available that show the use of the mail adapter and module configuration. However, using a Java mapping to create the whole MIME stream is the most flexible way to create a mail exactly in the way that it should look like.

 

The following code should show the basics of the MIME creation, feel free to use and enhance it to your needs:

 

Java Mapping to create MIME parts of an email
package sample;

import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import javax.xml.bind.DatatypeConverter;
import com.sap.aii.mapping.api.AbstractTransformation;
import com.sap.aii.mapping.api.StreamTransformationException;
import com.sap.aii.mapping.api.TransformationInput;
import com.sap.aii.mapping.api.TransformationOutput;

public class MyBinaryMessageAsAttachment extends AbstractTransformation {

  String attachmentName = "file.pdf";
  String boundary = "-" + "-" + "AaZz"; //
  String contentType = "multipart/mixed; boundary=\"" + boundary + "\"";
  String mailContent = "This is a sample file";
  String CRLF = "\r\n";

  public void transform (TransformationInput arg0, TransformationOutput arg1)  
                        throws StreamTransformationException {

    InputStream in = arg0.getInputPayload().getInputStream();
    OutputStream out = arg1.getOutputPayload().getOutputStream();
    try {
        // create the declaration of the MIME parts
        //First part
        String output = "-" + "-" + boundary + CRLF
               + "Content-Type: text/plain; charset=UTF-8" + CRLF
               + "Content-Disposition: inline" + CRLF + CRLF
               + mailContent // this should be some more useful text
               + CRLF + CRLF
    
        //Second part
               + "-" + "-" + boundary + CRLF
               + "Content-Transfer-Encoding: base64" + CRLF
               + "Content-Type: application/pdf; name=" 
               + attachmentName + CRLF
               + "Content-Disposition: attachment; filename=" 
               + attachmentName + CRLF + CRLF;
        out.write(output.getBytes());

        // convert InputStream to Byte array
        byte[] input = new byte[in.available()];
        in.read(input);
    
        // convert payload to base64
        output = DatatypeConverter.printBase64Binary(input);

        // split lines after 76 rows
        output = addLinefeeds(output);
        out.write(output.getBytes());

        // last boundary
        output = CRLF + CRLF + "-" + "-" + boundary + "-" + "-" + CRLF;
        out.write(output.getBytes());

        // set content type to message header
        arg1.getOutputHeader().setContentType(contentType);
    } catch (IOException e) {
        throw new StreamTransformationException(e.getMessage());
    }

  }




  public String addLinefeeds(String str) {

    StringBuffer result = new StringBuffer(str);
    int n = 76; // split by 76 characters (maximum of numbers in lines)
    int l = str.length();
    int i = n;

    while (l > n) {
        result.insert(i, CRLF);
        i = i + n + 2;
        l = l - n;
    }
    return result.toString();
  }

}

 

The Java Mapping will create two MIME parts. The first part is plain text, the second part is a binary, therefore we encode it to base64 and divide it into lines of no more than 76 characters each (which is the allowed maximum according to MIME protocol). The result will look like this:

 

Sample output of Java mapping

—-AaZz

Content-Type: text/plain; charset=UTF-8

Content-Disposition: inline

 

 

This is a sample file

 

 

—-AaZz

Content-Transfer-Encoding: base64

Content-Type: application/pdf; name=file.pdf

Content-Disposition: attachment; filename=file.pdf

 

 

PD94bWwgdmVyc2lvbj0iMS4wIiBlbmNvZGluZz0iVVRGLTgiPz4KPGNmZGk6Q29tcHJvYmFudGUg

cnRlPSIxNjA4Ni4xMyI+PC9jZmRpOlRyYXNsYWRvPjwvY2ZkaTpUcmFzbGFkb3M+PC9jZmRpOklt

cHVlc3Rvcz48Y2ZkaTpDb21wbGVtZW50bz48L2NmZGk6Q29tcGxlbWVudG8+PC9jZmRpOkNvbXBy

b2JhbnRlPg==

 

 

—-AaZz–

 

This scenario requires special settings of the Mail adapter channel.

It is very important that the mail attribute Use Mail Package is not checked, Content Encoding is set to None and Keep Attachments is not checked.

 

 

If you want to know, how the MIME parameters Content-Type and Content-Transfer-Encoding work, and which other parameters can be used, then look into RFC 1341 about MIME (Multipurpose Internet Mail Extensions): http://www.w3.org/Protocols/rfc1341/0_TableOfContents.html

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13 Comments

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  1. Anupam Ghosh

    Hi Stefan,

                        The pdf content is being encoded using base 64 encoding.

    The receiver has top decode the same I guess or he/she can read it just like PDF.

    Regards

    Anupam

    (0) 
      1. Evgeniy Kolmakov

        Hi Stefan!

        Thanks for another nice blog!

        One thing: wouldn’t you correct the phrase “into lines with 76 rows” in your record. I guess it should be something like “into lines with length of 76 symbols” there 🙂 .

        Regards, Evgeniy.

        (1) 
        1. Stefan Grube Post author

          Good point. The RFC1341 says: “The output stream (encoded bytes) must be represented in lines of no more than 76 characters each.” I corrected the phrase in my blog accordingly.

          (1) 
  2. Shyam Viswanatham

    Hey stefan,

    My requirement is to have a pdf attachment (xHTML) and a  static text in the body all the time. The interface is built as much as populating XHTML via XSLT and PDF renderer in an adapter module before calling the mail adapter.i am trying to add the body now.

    However, without deviating , i used your code and deployed it successfully and tried to run a simple test.I do get the output just a body without any attachments if i go by the channel config as well.

    Would you be able to shed any light on my requirement and generating an attchment and body via your code?

     

    Many thanks,

    Sam

     

     

    (0) 
  3. Shyam Viswanatham

    Hey Stefan, I used this code to see if an attachment is being created.While the code is being deployed and works, i do not see an attachment and the output you have shown is right but all of it comes in the body.I have made the channel settings exactly as you had mentioned.

     

    Can you please suggest how to get the attachment and the body text or am i doing anything wrong?

    (0) 
  4. Shyam Viswanatham

    Hey stefan,

     

    UPDATE: the code you have posted works fine.There was a final ‘-‘ missing for some reason in the final boundary condition and now its works perfect.

     

    MANY thanks once again to show this way forward.

    (0) 
  5. Prashant Bhavsar

    Hello Stefan,

    This is really useful post. I was able to get it working but both attachment contents and mail body are in the body.

     

    Hello Shyam,

    I am getting the same problem.

    Can you please share what you did to fix this?

     

    (0) 
    1. Stefan Grube Post author

      The font which is used for the Java code does not show the two minus (–) characters good, it appears as one character.

      Make sure that all boundaries start with two minus characters and the last boundary also ends with two minus characters.

      I changed the code to make it more obvious.

      (0) 

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