Limit user to post certain number of comments per article - spring

Question

Somehow I'm running in circles for two days! I have MySQL Database and comments table in witch I have id, user_id, date, published_at, body, likes and dislikes. How to limit user for max 10 comments per day. Of course I have user table.
I know I have somehow to count number of comments for certain date and put it in security context but I don't know how. I've tried with some native queries in
Repository like:
#Query(value = "select count from comments WHERE published_at=?1 AND user_id=?2", nativeQuery = true)
public int brojPostovaPoDanuPoUseru(Date datum, Integer user_id);
I guess I should find logged user name from SecurityContext and after that find his id, but then again what if there are two users with a same name, and where to use SecurityContext to find this.
At least some guidelines please :)

Answer 1

You can implement this on database level. My idea would be to save the time in seconds in date ( using Java: System.currentTimeMillis()). Then when you query by the user id, you can sort the results by date in descending order and filter for the top 10. Then you would pick the smallest number in date and check if it was less then 24h ago, if so you could then return an exception.
This would be an example query:
select * from (SELECT * FROM `comments` where comments.user_id=?1 ORDER BY `comments`.`date` DESC limit 10) as c order by c.date ASC limit 1
Let's say you saved date in secods using System.currentTimeMillis() / 1000. Now with the query result you would first calculate the seconds in hours and then in a day. This results in 86400 seconds. Now you would calculate the current time in seconds and extract it with the 24h in seconds as calculated before. And then you would check if this calculated result is smaller than the value of date this would indicate that the last 10th comment was made within the 24 hours.
This is the sample code in your repository:
#Query("select * from (SELECT * FROM `comments` where comments.user_id=?1 ORDER BY `comments`.`date` DESC limit 10) as c order by c.date ASC limit 1", nativeQuery=true)
public Comments getLastTenthComment(int userId);
This is the sample code in your service:
public boolean isAllowedToComment(int userId){
Comment comment = repository.getLastTenthComment(userId);
int dayInSeconds = 86400;
long currentTime = System.currentTimeMillis() / 1000;
long yesterdayInSeconds = currentTime - dayInSeconds;
if(comment.getDate() >= yesterdayInSeconds){
return false;
}
return true;
}