<p>In order to handle concurrency issue, is locking-- any form of locking, whether it's row, table or database locking a good solution?</p>

<p><strong>If not, how to handle concurrency issue?</strong></p>

I think not, because it is all the way "down" and makes your application more complex. Most languages have excelent concurrency handling techniques, and even then the best way is to write code which can handle concurrency "natively".
For more info on concurrency in Java:
http://java.sun.com/docs/books/tutorial/essential/concurrency/index.html