@Stateful(name="stateful")
@Local(Session.class)
public class StatefulSessionBean
implements Session {
private int result;
@Override
public void add() {
result++;
}
@Override
public int get() {
return result;
}
}
Then create a servlet to Dependency Inject the stateful session bean
public class StatefulDependencyInjectionServlet
extends HttpServlet {
@EJB(beanName="stateful")
private Session stateful;
@Override
protected void doGet(HttpServletRequest req,
HttpServletResponse resp)
throws ServletException, IOException {
HttpSession session = req.getSession(true);
Session bean = (Session)session.getAttribute("stateful");
if (bean == null){
bean = this.stateful;
}
bean.add();
System.out.println("Stateful: " + bean.get());
session.setAttribute("stateful", bean);
}
}
Test the servlet several times and check the result
[24/08/11 14:30:00:234 EST] 00000016 SystemOut O Stateful: 1
[24/08/11 14:30:03:234 EST] 00000016 SystemOut O Stateful: 2
[24/08/11 14:30:06:203 EST] 00000016 SystemOut O Stateful: 3
It seems working fine. But if we close the browser, open it again and test the servlet several times, we will see:
[24/08/11 14:33:15:812 EST] 00000016 SystemOut O Stateful: 4
[24/08/11 14:33:16:718 EST] 00000016 SystemOut O Stateful: 5
[24/08/11 14:33:17:328 EST] 00000016 SystemOut O Stateful: 6
This behaviour is incorrect as when the browser is closed and reopened, it represents a new client, who should get a new instance of stateful session bean.
Now create another servlet to access the stateful session bean through Context Lookup.
@EJB(name="ejb/stateful",
beanInterface=Session.class,
beanName="stateful")
public class StatefulContextLookupServlet
extends HttpServlet {
@Override
protected void doGet(HttpServletRequest req,
HttpServletResponse resp)
throws ServletException, IOException {
HttpSession session = req.getSession(true);
Session stateful = (Session)session.getAttribute("stateful");
if (stateful == null){
try{
Context ctx = new InitialContext();
stateful = (Session)ctx.lookup
("java:comp/env/ejb/stateful");
}catch (Exception e) {
throw new EJBException(e);
}
}
stateful.add();
System.out.println("Stateful: "+stateful.get());
session.setAttribute("stateful", stateful);
}
}
Test the servlet several times and check the result
[24/08/11 14:38:42:250 EST] 00000016 SystemOut O Stateful: 1
[24/08/11 14:38:45:453 EST] 00000016 SystemOut O Stateful: 2
[24/08/11 14:38:46:000 EST] 00000016 SystemOut O Stateful: 3
Close the browser, open it again and test the servlet several times
[24/08/11 14:39:38:734 EST] 00000016 SystemOut O Stateful: 1
[24/08/11 14:39:39:796 EST] 00000016 SystemOut O Stateful: 2
[24/08/11 14:39:40:546 EST] 00000016 SystemOut O Stateful: 3
Now the behaviour is correct.
