I am reading MySQL maual about AUTO_INCREMENT field, which indicates that "An AUTO_INCREMENT column works properly only if it contains only positive values".

a SQL snippet generated by MySQL QueryBrowser as following:

CREATE TABLE `user` (
`USER_ID` int(10) unsigned NOT NULL auto_increment,
`NAME` varchar(255) NOT NULL default '',
PRIMARY KEY (`USER_ID`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;

MySQL unsigned INTEGER type range from 0 to 4294967295, but Java int type range from -2147483648 to 2147483647, the USER_ID will be increased day by day, then exceeds max value 2147483647, and then.... does that means that if i mapping DB INT AUTO_INCREMENT with java int is a bad practice? anyone has any suggestions?

Well, yes, if you expect your database to grow beyond that size. But then you'll have trouble with MySQL's range as well. And, considering that the size of a database with this many entities would be a couple hundred gigabytes at least, you probably won't use MySQL for that task anyway.

So, first do a little math to see if this could be a problem for you. I'm pretty sure you'll find out it isn't.