private String generateBoundary() {

		final char[] BOUNDARY_CHARS = "-_1234567890abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ".toCharArray();
		final String BOUNDARY_BASE = "---BOUNDARY-";

		StringBuilder buffer = new StringBuilder();
		buffer.append(BOUNDARY_BASE);
		Random rand = new Random();
		int count = rand.nextInt(11) + 30; // count between 30 and 40
		for (int i = 0; i < count; i++) {
			buffer.append(BOUNDARY_CHARS[rand.nextInt(BOUNDARY_CHARS.length)]);
		}
		return buffer.toString();
	}