rowCount and EntityManager

[schnulla]

Hello,

I want to see how many users are registered:

<h:outputText styleClass="outputText" value="#{userList.rowCount} Users"/>

@Stateless
@Name("registrationStats")
public class RegistrationStats implements RegistrationStatsInterface {
     
     @PersistenceContext
     private EntityManager entityManager;
     
     @DataModel     
     private List<User> userList;
     
     @Factory("userList")
     public void populateUserList() {
          userList = entityManager.createQuery("SELECT COUNT(*) FROM User").getResultList();
     }
}

@Local
public interface RegistrationStatsInterface {     
     public void populateUserList();
}

But I always get 1 user registered.

Please can you help me?

[dhcinc]

In your query, you are asking for a count of the number of users. As such, you will always get one row back from the select.

Perhaps you meant to use SELECT user from User user?

[schnulla]

You are right it must be SELECT user from User. Thank you!

I wonder how I could use COUNT() and outject that value
to my h:outputText? And how-to update this value because
at the moment DataModel is only populated on the first
page visit.

Thanks for any hints :)

[schnulla]

You are right it must be SELECT user from User. Thank you!

uups I meant SELECT name from User

[meetoblivion]

well if you want to outject the count, you could do something like this:

private BigDecimal userListSize;

@Factory("userListSize")
public void populateUserListSize() {
userListSize = entityManager.createQuery("SELECT COUNT(*) FROM User").getSingleResult();
}

or you could use the existing userList

private BigDecimal userListSize;

@Factory("userListSize")
public void populateUserListSize() {
userListSize = userList.size();
}

[schnulla]

Thanks the first works fine and this way I get
rid of the @DataModel and .rowCount stuff :)

I guess COUNT() is also more performant than
SELECT user FROM User?

The only thing I have to solve now is to
update userListSize on every page visit.
What is the standard practice to do this?

Thanks for the help :)