Android™

MIME Body vs. Sub-Parts

See more MIME Examples

Explains the difference between sub-parts and body.

MIME documents (i.e. messages) can have a nested structure. The simplest MIME message contains a header followed by content (possibly encoded). The header is delimited from the content by two consecutive CRLF's.

A MIME message may be multipart. If so, then the Content-Type header field indicates "multipart" and the content the follows the header is itself a MIME message, which may also be multipart, etc. You can see how MIME messages effectively have a tree structure. The non-leaf nodes have Content-Types that are "multipart/" and the leaf nodes have non-multipart Content-Types.

The Chilkat MIME component/library uses two terms that need to be understood in order to effectively use the API. These are "body" and "sub-part". A multipart node has 1 or more sub-parts, but its body is empty. A leaf node (i.e. non-multipart node) has no sub-parts, but the body is (usually) non-empty.

This example creates a multipart MIME message and shows the results of getting the sub-parts and body of each node.

Android™

// Important: Don't forget to include the call to System.loadLibrary
// as shown at the bottom of this code sample.
package com.test;

import android.app.Activity;
import com.chilkatsoft.*;

import android.widget.TextView;
import android.os.Bundle;

public class SimpleActivity extends Activity {

  private static final String TAG = "Chilkat";

  // Called when the activity is first created.
  @Override
  public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);

    boolean success = false;

    //  This example assumes the Chilkat API to have been previously unlocked.
    //  See Global Unlock Sample for sample code.

    CkMime mime = new CkMime();

    //  Create a multipart/mixed MIME message with two sub-parts.
    //  We'll use the Base64 encoding for the 2nd sub-part.
    CkMime part1 = new CkMime();
    success = part1.SetBodyFromPlainText("This is part 1");

    CkMime part2 = new CkMime();
    success = part2.SetBodyFromPlainText("This is part 2");
    part2.put_Encoding("base64");

    success = mime.NewMultipartMixed();
    mime.put_UseMmDescription(false);
    success = mime.AppendPart(part1);
    success = mime.AppendPart(part2);

    //  Show the MIME message:
    Log.i(TAG, mime.getMime());

    //  Here's the MIME:
    //  Content-Type: multipart/mixed;
    //  	boundary="------------040605030407000302060008";
    //  
    //  --------------040605030407000302060008
    //  Content-Type: text/plain;
    //  	 charset="us-ascii";
    //  Content-Transfer-Encoding: 7bit
    //  
    //  This is part 1
    //  --------------040605030407000302060008
    //  Content-Type: text/plain;
    //  	 charset="us-ascii";
    //  Content-Transfer-Encoding: base64
    //  
    //  VGhpcyBpcyBwYXJ0IDI=
    //  
    //  --------------040605030407000302060008--

    //  If we examine the root node of the MIME message, 
    //  we see that it has 2 sub-parts and the body is empty (as expected)
    int n = mime.get_NumParts();
    Log.i(TAG, "Num Parts = " + String.valueOf(n));
    Log.i(TAG, "Body = " + mime.getBodyDecoded());

    //  The GetEntireBody retrieves the entire content after
    //  the header.  (Perhaps GetEntireBody should've been named
    //  GetEntireContent to make it less confusing...)
    Log.i(TAG, "---- EntireBody:");
    Log.i(TAG, mime.getEntireBody());
    Log.i(TAG, "********");

    //  Now examine the 2nd sub-part.  It has a body encoded
    //  using base64.  Get the contents of the body in both
    //  decoded and encoded forms:

    //  index 0 is the 1st part, index 1 is the 2nd part.
    CkMime part = new CkMime();
    mime.PartAt(1,part);

    Log.i(TAG, "Decoded Body:");
    Log.i(TAG, part.getBodyDecoded());
    Log.i(TAG, "Encoded Body:");
    Log.i(TAG, part.getBodyEncoded());

  }

  static {
      System.loadLibrary("chilkat");

      // Note: If the incorrect library name is passed to System.loadLibrary,
      // then you will see the following error message at application startup:
      //"The application <your-application-name> has stopped unexpectedly. Please try again."
  }
}