Problems with Requests

Question

          Hi,
          i am using weblogic in my project both as a webserver and as the application server.
          But i am facing problems with requests being sent to the server. Basically i have
          a form in my jsp which, if submitted by multiple clients at the same instant in
          time, the server gets confused and mixes up the data in the requests !! the form
          is submitted to another jsp which in turn calls a SLSB which in turn calls various
          entity Beans to fulfill the request.
          Now if 2 or more clients hit the submit button together, the server is mixing
          the data from the requestsand i get corrupted output as a result.
          That if i submit values (a,b,c) from one client machine and values (x,y,z) from
          another machine, the server puts one of the transactions properly and in the other
          it picks up the data from the other request and takes something like (x,y,c) !!
          Is this a bug in Weblogic 6.1 or am doing something wrong ?? Anyone faced this
          problem ?
          Any help would be appreciated.
          Raja
          

Answer 1

Hi,
          It's highly unlikely that it's WebLogic. Somewhere along the line, you are
          calling or referring to the same instance of either a class of a variable.
          You should brush up on the meaning of static variables.
          Make sure that you are not using class-level variables in your servlet. WLS
          will create only one instance of a Servlet or JSP and invoke it from
          multiple threads (requests) unless it is declared as SingleThreadModel. (See
          the servlet spec).
          When you declare variables inside a method - they are defined on the stack -
          so they're safe from multiple threads since each thread has it's own stack.
          If you declare them in a class, they're on the heap, and are shared by
          multiple threads invoking that servlet-class instance.
          There is a workaround if you MUST use class-level variables (not a good idea
          in a servlet). You can declare your Servlet (or JSP) as SingleThreadModel.
          This is less desirable since it carries a performance hit. It's best to
          design around it - but you might try declaring this to see if it helps in
          the JSP...
          <%@ page isThreadSafe="false" %>
          Of course, if the threading issues I've discussed above are occurring
          elsewhere in your code, you'll have to design-around it. Like I say, check
          for static class variables. It's unlikely that your other code is invoking
          the same instances of other classes from multiple threads (unless those
          instances are servlet-class-variables - and your problem will be resolved by
          the above).
          Make sure that you are not referencing static variables in your servlet or
          other bean classes (unless you intend to). Static variables are scoped at
          the class level and are therefore shared by all instances of that class (or
          servlet). The above SingleThreadModel won't help you in that case since all
          instances of the same class will be using the same static variables.
          Hope that helps,
          Alex
          "Raja" <[email protected]> wrote in message
          news:[email protected]...
          >
          > Hi,
          > i am using weblogic in my project both as a webserver and as the
          application server.
          > But i am facing problems with requests being sent to the server. Basically
          i have
          > a form in my jsp which, if submitted by multiple clients at the same
          instant in
          > time, the server gets confused and mixes up the data in the requests !!
          the form
          > is submitted to another jsp which in turn calls a SLSB which in turn calls
          various
          > entity Beans to fulfill the request.
          > Now if 2 or more clients hit the submit button together, the server is
          mixing
          > the data from the requestsand i get corrupted output as a result.
          > That if i submit values (a,b,c) from one client machine and values (x,y,z)
          from
          > another machine, the server puts one of the transactions properly and in
          the other
          > it picks up the data from the other request and takes something like
          (x,y,c) !!
          > Is this a bug in Weblogic 6.1 or am doing something wrong ?? Anyone faced
          this
          > problem ?
          > Any help would be appreciated.
          >
          > Raja
          >
          >