I am working on a Spring MVC project. I am having issue with getting null values from database after some time interval. Following is the method written in DAO which return last entered value.

@Override
public String getDashboardData() {
    String q = "SELECT deviceid FROM main_tbl order by id DESC limit 1";
    String newId = jdbcTemplate.queryForObject(q, String.class);
    System.out.println(newId);
    return newId;
}

This method is called from jsp with every 1 sec. My problem is that, this method returns bunch of some values & null value alternately. I didn't get the actual reason because everything works fine.

My output is like below:

01
05
09
41
null
null
null
null
15
09
05
65
10
null
null
null
null 

Is that problem with postgresql..? Or is their any that I missed. I’ll be very grateful for any help!