Synchronized problem in JSP/Servlet, please help me.

Question

Hi, all
I have many processes in one JSP page or Servlet program of my project.
When many people visit at one time, then the project throws some SQL/DB Errors.
I have updated it and test it many times, I think, that is a synchronized problem.
At last I used ��synchronized (this){my JSP/Servlt SQL/DB processes}�� to synchronize
The process. Then the errors removed.
And now I think that too danger to use the ��synchronized (this){}�� to synchronized.
If use it then some other problem may be growling on. Such as when one people need to use
This service others must to wait, the process may be too slow! And when an exception throws
from the SQL/DB or some other place, what I do? Need any advice from you.
Sincerely
Urey
*** my JSP/Servlt Server is tomcat ***

Answer 1

As Chuck points out, there isn't a new instance of the Servlet/JSP for each request - they are probably all calling the same instance so any state will be shared. If your Connection is stored as a member variable then you'll have problems with it already being in use if two people hit the page at the same time.
Limited resources such as database connections should ideally be pooled anyway to ensure that you're not opening them all the time and that you can control how many are open across the entire application. Then you'd simply need to get a fresh connection out of the pool at the top of the page and make sure you put it back when you're done.
Incidentally, although it might work, synchronizing the database access in the JSP would be a bad idea since you'd just create a queue of requests waiting to use the one Connection whereas you really need a number of Connections to deal with everyone simultaneously.
If you need some example code for a simple JSP using a database connection pool (DataSource) just say.
Hope this helps.