How I can genarate Unique Random number and store in mysql table in spring boot

I want to develop an Spring boot web application where I can generate sets of number and store in a table. For example

This is my controller

@RequestMapping("/testInteger")
    public String genint(com.randomdata.entity.Random random) {
        
        
        int intRange;
        try {
            
            for (int i = 0; i < 10; i++) {
                intRange = generateRandomIntIntRange(1000, 10000);
                String string = Integer.toString(intRange);
                random.setRandomNumber(string);
                randomDao.save(random);
            }
        } catch (Exception e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        
        return "index";
        
    }

This is my random number generating method.

public static int generateRandomIntIntRange(int min, int max) {
        Random r = new Random();
        return r.nextInt((max - min) + 1) + min;
        
    }

But it's can save 1 number in db table and others showing

Hibernate: update random set random_number=? where id=?
Hibernate: update random set random_number=? where id=?
Hibernate: update random set random_number=? where id=?
Hibernate: update random set random_number=? where id=?
Hibernate: update random set random_number=? where id=?
Hibernate: update random set random_number=? where id=?
Hibernate: update random set random_number=? where id=?
Hibernate: update random set random_number=? where id=?
Hibernate: update random set random_number=? where id=?

Of course, I missed something. but I cannot find yet.