Java Random number getting repeat issue

I have a system which communicate to external system via webservices in which we used to send random nos as msg id and same is getting stored as a primary key of table in our database. Problem here is since we have approx 80-90 k call on daily basis i have seen so many exceptions saying that duplicate primary key. I am generating random nos in java. How can i be sure that whatever random number i will generate will not be duplicated.

below is code for the generating random nos:

private static int getRandomNumberInRange(int min, int max) {

    if (min >= max) {
        throw new IllegalArgumentException("max must be greater than min");
    }

    Random r = new Random();
    return r.nextInt((max - min) + 1) + min;
}