ql and COUNT() - return type ?

[nefilim]

Hi,

I don't know if this is the best way to do it but I figured it's less expensive to have a select method in the home interface of a cmp that counts the amount of rows for a specific condition than to find them all and count the collection.

The problem is though, according to Denniger & Peter's EJB 2.1 select methods can only return type of remote or local interface or of a persistent attribute. So I come up with this query:

SELECT COUNT(p.id) FROM User AS p WHERE p.deptId=?1

However, deploying on JBoss 3.2.2 I get the following error:

(org.jboss.ejb.plugins.cmp.ejbql.ParseException: Encountered "COUNT" at line 1, column 8.
Was expecting one of:
"DISTINCT" ...
"OBJECT" ...
<NUMERIC_VALUED_PATH> ...
<STRING_VALUED_PATH> ...
<DATETIME_VALUED_PATH> ...
<BOOLEAN_VALUED_PATH> ...
<ENTITY_VALUED_PATH> ...
<VALUE_CLASS_VALUED_PATH> ...
)

Is COUNT() not supported yet or am I not using it correctly? Btw, what does one do if the primary key is not numeric, the return type would not match the persistent attribute type? Is there a better way of achieving this?

Many thanks,
Peter

[draftdog]

hi Peter,

make sure you implement this method as an select method and not as a finder method

assuming you're using xdoclet you will need to add a class-level tag @ejb.select and specify the query there, you will then also need to write a method for this query

there are many examples to be found on the internet that explain how to achieve this, but let me point you to a working example of mine, it is a bean generated by AndroMDA using a custom template, it automatically generates some default finders and selects

http://cvs.sourceforge.net/viewcvs.py/jeteam/ejb/src/java/org/jeteam/business/note/NoteBean.java?view=markup

my primary keys are Strings while the COUNT returns a java.lang.Long


hth
Wouter.

[draftdog]

correction, it is not @ejb.select but @jboss.query you will need to add at the class level

this will make ejbdoclet render this as JBoss-QL (also notice the 'dynamic' attribute (for dynamic-ql)

anyway, taking a look at the tags + methods should give you an idea