Thank you very much. You are right - the problem was in the DAO !! Valli IIC SSS INDIA
-----Original Message----- From: Paul Hodgetts [mailto:[EMAIL PROTECTED]] Sent: Monday, January 27, 2003 1:19 AM To: Struts Users Mailing List Subject: RE: Newbie: Action class - how to make it thread safe? Sowbhagya Valli Suryadevara wrote: > We are using the struts(1.0.2) framework in our application. > When multiple users are clicking on the same SAVE button > simultaneously the data is getting interchanged for the users. > > Am I supposed to synchronize any of the blocks? The sample > code provided by struts does not have any synchronized > blocks. If required then should it be for accessing the > session and the dao ?? [original sample code below...] mech responded: > So you could either try for example to synchronize only the block after > checking for "saveUser". Could already solve your problem. Or try to > make your DAOs thread-safe. It's a really bad idea to introduce synchronized blocks into methods in the request processing chain. This can have serious negative repercussions for scalability. If some protection is needed for concurrent access to data, such as might occur if multiple clients are updating the same record, that should be handled at the database level with transactions and strategies for preventing updates with stale data (e.g., time stamps). A few observations: * The data seems to be coming from the session. Assuming there is no sharing of session IDs across clients, the data should be unique per client request. * The action seems to be using only local variables. The data in these variables should be unique to the thread, and thus the client request. * You are doing a database insert, which presumably is creating a new record for each client request. I'm assuming there are either constraints at the database level for unique keys, or you don't care about unique keys and every insert creates a new record, even with duplicate data, so the database insert should be unique per client request. In short, unless I've missed something in the small block of sample code in the original post, there is nothing that indicates there should any conflict between clients as described. There must be more to this story. It doesn't seem like it has anything to do with Struts. It's possible the DAO, or maybe the form object depending on how you wrote it, have some static variables that might be shared. The DAO looks like it might be a singleton, so it's possible it is sharing some instance data. But that's not visible from the example. FWIW, you really shouldn't be using your form as a domain object and passing it all the way to the persistence tier, thus coupling the tiers. It's a better design pattern to have the action transfer the needed values out of the form into a domain object, or into a data transfer/value object, and then pass that around instead. Also, as a matter of naming style calling something a "Session Bean" is very confusing when J2EE has something called a Session Bean that is widely used and means something entirely different. Regards, Paul ----- Paul Hodgetts -- President, Principal Consultant Agile Logic -- www.agilelogic.com Consulting, Coaching, Training -- On-Site & Out-Sourced Development Java, J2EE, C++, OOA/D -- Agile Methods/XP/Scrum, Use Cases, UI/IA -----Original Sample Code----- public class UserActions extends Action { public ActionForward perform(ActionMapping mapping, ActionForm form, HttpServletRequest request, HttpServletResponse response) throws IOException, ServletException { String actionType = request.getParameter("actionType"); HttpSession session = request.getSession(); MessageResources messageResources = getResources(); // getting user-specific values from the session MSSessionBean sessionBean = (MSSessionBean)session.getAttribute(MSSessionBean.SESSION_PARAM); // for saving the user if (actionType.equals("saveUser")) { int companyId = sessionBean.getCompanyId(); String strUserId = sessionBean.getUserId(); Locale userLocale = sessionBean.getUserLocale(); PersonForm person = (PersonForm) form; // calling the data access object to insert into the data base PersonDAO personDAO = PersonDAO.getInstance(); personDAO.insert(person); } } -- To unsubscribe, e-mail: <mailto:[EMAIL PROTECTED]> For additional commands, e-mail: <mailto:[EMAIL PROTECTED]> --------------------------------------------------------------------- To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED]
