Hi,
If u want to threadsafe there is two ways.
One is implements SingleThreadModel. But this will give good
result but performance will be poor.
Another way is u can synchronize some code using synchronized
block(mainly database statements which ever is necessary). Take care
when ever createing Object's globally in servlets. Bye.
On Apr 12, 2005 7:24 AM, Brett Zamora <[EMAIL PROTECTED]> wrote:
> Hi...
>
> I'm trying to build a JSP/Servlet application that will retrieve, add,
> update, and delete records from a database. I've recently encountered some
> of the complications that can be seen if a servlet is not written to be
> thread safe.
>
> First I'd like to say that I've been reading and reading on this issue and I
> thought I had a pretty good grasp on the subject, however, I still cannot
> eliminate the condition I am experiencing.
>
> The problem I'm seeing is when I first start up my application server,
> either Tomcat or Resin, and I run my application, which retrieves records to
> be displayed from the database, invalid data is displayed in some of the
> fields. Basically, the instance variables for the bean class are being
> trashed.
>
> I can only create this condition the first time after I stop and restart the
> application server. After the first occurrence, it does not seem to
> continue. This doesn't mean the condition doesn't exist, just that I can't
> seem to recreate it.
>
> I have set up a sample of the problem at http://www.zware.net/simpleDemo
>
> It is a very basic, very small sample amount of code that does what I
> outlined on the simple demo page. I've also provided the source code, so
> that anybody that might be willing to help me, could see how I am attempting
> to synchronize my code to avoid the condition I am seeing.
>
> In a nutshell, I create a bean for the user record. I then synchronize the
> bean and call a method to retrieve the data. Before exiting the synchronize
> block, I add the bean to the session object. I then exit the synchronize
> block and forward control to the jsp page to display the data.
>
> As I said, I can only cause the condition to occur in a very specific way,
> however, I'm inclined to believe that I'm doing something drastically wrong
> and I am afraid to continue developing anything until I completely
> understand how to avoid the multi-threading problem that I seem to be
> experiencing.
>
> I would appreciate any feedback that anybody could provide on what I've done
> wrong. Please don't slam me for code structure. This simple app was put
> together to be readable and to solicit some assistance with my
> use/understanding of how to synchronize an object.
>
> Synchronization seems pretty straight-forward, conceptually, however, I
> cannot resolve this issue. I've even gone so far as to use the implements
> SingleThreadModel on the SimpleCtl class, but this still does not resolve
> the condition.
>
> I'm wondering if it could be my JDBC driver? My backend database is MySql
> and I've tried a couple of version 3.x JDBC drivers, but again, I cannot
> resolve the problem.
>
> Any help is greatly appreciated.
>
> Regards,
>
> Brett
>
> Sample: http://www.zware.net/simpleDemo
>
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--
P.Narendra Krishna, MCA.
(9892950229)
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