InputStream inputStream = getClass().getResourceAsStream("image.jpg");
// ...

import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.InputStream;

/**
 * Constructs a byte array and fills it with data that is read from the
 * specified resource.
 * @param filename the path to the resource
 * @return the specified resource as a byte array
 * @throws java.io.IOException if the resource cannot be read, or the
 *   bytes cannot be written, or the streams cannot be closed
 */
private byte[] obtainByteData(String filename) throws IOException {
    InputStream inputStream = getClass().getResourceAsStream(filename);
    ByteArrayOutputStream outputStream = new ByteArrayOutputStream();
 
    // Read bytes from the input stream in bytes.length-sized chunks and write
    // them into the output stream
    for (int readBytes = inputStream.read(); readBytes >= 0; readBytes = inputStream.read())
        outputStream.write(readBytes);
 
    // Convert the contents of the output stream into a byte array
    byte[] byteData = outputStream.toByteArray();
 
    // Close the streams
    inputStream.close();
    outputStream.close();
 
    return byteData;
}

import javax.wireless.messaging.MessagePart;
import javax.wireless.messaging.SizeExceededException;
 
// ...
 
/**
 * Constructs a MessagePart which can be added to a MultipartMessage.
 * @return the constructed MessagePart
 * @throws javax.wireless.messaging.SizeExceededException if the contents
 *   is larger than the available memory or supported size for the message
 *   part
 * @throws java.io.IOException if the byte data cannot be obtained
 */
private MessagePart createMsgPart() throws SizeExceededException,
        IOException {
    String imageContentID = "image01";
    String imageContentLocation = "image.jpg";
    String jpgMIME = "image/jpeg";
    // Convert the image into a byte array and construct a message part using
    // it
    byte[] imageContent = obtainByteData(imageContentLocation);
    MessagePart messagePart = new MessagePart(imageContent, jpgMIME,
            imageContentID, imageContentLocation, null);
    return messagePart;
}